Mauerlat is: cross-section, mounting angle and extension, purpose and fastening rules

Mauerlat is a special belt laid around the perimeter of the upper end of the external load-bearing wall of the building and intended for attaching rafter legs. Wood is considered a traditional material for the manufacture of this element of the rafter system, but if a metal frame is installed under the roof, then rolled metal - I-beams, channels or profiles - can also be installed as a Mauerlat.

It is relatively easy to install a Mauerlat for a gable roof with your own hands - there are several different technologies for this. But it should be remembered that the more securely it is fixed to the wall, the longer the service life of the entire structure of the rafter system will become.

Wall mounting methods

Correctly fastening the Mauerlat to the walls will ensure its reliable operation.
Depending on the type of base, attachment points are made in four ways.

Fastening with anchor bolts. The anchors are laid in advance in a reinforced concrete belt made along the edge of the wall. This method is suitable for relatively soft walls made of concrete blocks. The belt allows you to distribute the concentrated load from the roof even more efficiently. Anchors should be fastened at intervals of at least rafter spacing

It is important to think about the location so that it falls on the spaces between the rafter legs. The Mauerlat is installed on anchors and pulled to the wall

This method provides the most rigid connection possible, but is characterized by the highest cost;

Fastening with pins. This type of fastening is suitable for small brick buildings. L-shaped studs are laid into the brickwork with the curved end down. The laying depth is assumed to be at least 45 centimeters. The length of the stud should be selected so that it passes through the Mauerlat and allows fastening with nuts. The cross section of the stud is 12 - 16 millimeters. The waterproofing layer between the wall and the Mauerlat is also pinned onto studs. With this method, the upper layers of the masonry are reinforced with additional reinforcing mesh;

Fastening with staples. Wooden blocks are installed into the masonry 2–3 rows below the edge of the wall. The brackets are attached to these bars from below, and to the Mauerlat from above. This method does not damage the waterproofing layer.

If the Mauerlat is installed directly on brickwork or on aerated concrete blocks, a point load will occur. As a result, the wall may collapse. Armopoyas is the solution to this problem.

Basic methods of installing a Mauerlat

Having chosen the material for making the base for the rafters, you need to decide whether a reinforcing belt will be poured along the top of the wall. This structural element is reinforcing and is usually installed on block, brick or fill walls, giving the roof a reliable foundation. If the walls are monolithic, or the brickwork is made in several rows in thickness, then the reinforcing belt is abandoned in order to simplify the work, save money and lighten the entire structure of the house.

Thus, there are two types of arrangement of the base for the Mauerlat - with and without filling the reinforcing belt.

To ensure high-quality ventilation of the attic space and avoid rotting of wooden structural elements, experts recommend fixing the Mauerlat 300÷500 mm above the attic floor beams.

Attaching the Mauerlat to the walls can be done in various ways, depending on the existing base:

The mauerlat beam along the entire perimeter of the building is rigidly connected into a single frame. Since lumber usually has a standard length of 6 m, the mauerlat is assembled from several pieces of timber. They are spliced together with an oblique cut or half-timber, and the joint is additionally fastened with self-tapping screws, screws or wooden dowels.

The corner units of the frame are fastened with metal plates or brackets. The frame can additionally be fixed with brackets to the wall. One side of this element is driven into the Mauerlat, and the other into the wall. In the presented mounting diagram for the Mauerlat, this type of fixation is shown on the left side.

A half-wood connection can be made using a pin embedded in the wall in advance, or with anchors driven into the through holes of the combined parts of the beam.

This type of fixation of the Mauerlat to the walls is possible without a reinforcing belt.

On the right side of the diagram presented above, the installation of timber on a reinforced concrete belt is shown, into which studs are embedded at a certain distance to secure the Mauerlat to them.

This installation method is used for lightweight backfill walls or those built from foam concrete and gas silicate blocks. In such a design, the main load from the rafter system falls on the reinforcing belt, and the Mauerlat distributes it evenly along the entire perimeter.

Let's consider both cases - with and without a reinforcing belt, in more detail

Installing a Mauerlat on a wall without a reinforcing belt

Basic installation and mounting options

There are four options for installing a mauerlat on a brick wall without a reinforcing belt. The simplest and therefore most common is when the beam is fixed on top of the wall to a waterproofing material:

— For the entire thickness of the wall surface, when the walls are one brick thick.

— At the level of the inner surface of the wall, into which a wooden plug ¼ brick deep is embedded below the upper end. In this case, the bracket is driven into the Mauerlat and the plug.

— At the level of the inner surface of the wall, on the upper edge of which, in front of the Mauerlat on its outer side, a wooden plug beam of a smaller cross-section, treated with a bitumen primer, is fixed.

- At the level of the inner surface of the wall, on top of a cork board pre-fixed on it, having the height of a brick.

The installation of a wooden Mauerlat on the wall is thought out in advance, taking into account the preparatory stage, which is carried out even when laying the walls:

The masonry rises above the floor beams by three or four brick courses. The surface of the wall must be flat. Then another row of brick is laid, but on the inside of the wall, instead of a brick, a processed timber plug is installed, having a thickness equal to the height of the brick.

Then another brick row is laid on top, covering the auxiliary wooden element.

Next, a waterproofing material is laid along the inner edge of the wall, on top of which a mauerlat beam is laid. On the remaining surface of the width of the wall, next to the Mauerlat, another row of brick is laid - this will protect the wooden part from external moisture. On this horizontal side, the timber must also be separated from the brick by a layer of waterproofing

After the mortar in the masonry has completely hardened, a bracket is driven into the mauerlat and the auxiliary beam-plug, which secures the wooden base to the wall.

rafter mount

In the second case, the wall is laid entirely from brick to the required height. When laying the next row, approximately in the middle of the wall thickness, wooden plugs treated with bitumen are installed, and a “shelf” for the mauerlat is left on the inside. On the outside, next to the cork, a brick is placed. Next, waterproofing is spread over the surface, and a Mauerlat is fixed on top of it, which is secured with staples to the plugs.
In the third option, all work is carried out in the same way as the second, but the masonry ends two rows before the desired height. Then, at the level of the inner edge of the end of the wall, plugs impregnated with bitumen are embedded, having a width greater than the width of the mauerlat, by approximately 50÷60 mm, and a height equal to the height of the brick. Next to them, a row of bricks is placed the width of the wall or with a protrusion outward. On top of the wooden plug, at a distance of 10–15 mm from its inner edge, a mauerlat is laid, which is covered from the outside with one row of bricks.

The masonry is carried out with a shift of bricks outward by 30÷50 mm, while a stepped ledge is formed. Due to the fact that the outer brick row rises above the level of fastening the Mauerlat, additional thermal insulation of the structure is provided, which is not observed in the simplest fastening option, when a wooden beam is simply installed on the waterproofed upper end of the wall.

It is worth paying attention to waterproofing. This material is installed so that it separates the raw wood from the brick or other masonry material. For waterproofing, not only roofing material can be used, but also linokrom, technoNIKOL or hydroisol.

Fasteners

The Mauerlat can be finally fixed to the wall in various ways - with staples, wire, threaded rods or anchor bolts. How this is done will be discussed below.

Wire twist

If you plan to fasten the Mauerlat with twisted wire, then it is laid along the inner edge of the wall, and brickwork is done along the outer edge.

To work, you will need steel wire - “rod rod”, having a diameter of 5 ÷ 6 mm. It is laid at the stage of wall construction 4-5 rows of masonry to the top, usually folded in half. The free length of the ends of the wire on both sides of the wall should be left so that it is enough for twisting on the inner edge of the installed Mauerlat.

The twisting itself is carried out using a pry bar or crowbar.

Another option for fastening the Mauerlat by twisting is to pass the ends of pre-embedded wire through through holes drilled in the timber.

In this case, the wire is raised from both sides to the edge of the wall, then it is bent and passed through the through holes of the Mauerlat from below, and then twisted so that the beam is tightly pressed to the upper surface of the wall. Fastening using twisting is carried out in steps equal to the step of installing the rafters - the connecting nodes are between adjacent rafter legs.

Staple fastening

As mentioned above, in some cases, wooden plugs are embedded into the brickwork, which have a width and height equal to the size of the brick. Sometimes they use a cork made of timber, running along the entire wall parallel to the mauerlat.

Corks must be carefully treated (impregnated) with a bitumen primer to prevent the wood from absorbing atmospheric moisture. The insertion of wooden plugs has already been described above, and all that remains is to consider attaching the Mauerlat to them using staples.

In order for the bracket to fit neatly into the wood without splitting it in two, it is recommended to drill holes according to the markings, equal in diameter to the ends of the bracket. Then the bracket is installed in the designated holes and driven into them with a hammer.

Installing the Mauerlat on studs

Another option for fastening the Mauerlat is to install it on metal threaded rods or on reinforcement rods embedded in the masonry. This fastening method is used if the walls of the building will bear a high load. The studs are usually placed between the rafters at a distance equal to the installation pitch of the rafter legs. This distance can sometimes be increased, but in any case it should not exceed 1500 mm.

Fastening is performed in the following order:

Sections of reinforcement are prepared, bent in the lower part in the form of the letter L, or studs with a diameter of 10÷14 mm, in the lower part of which a horizontal section having a length equal to the length of the brick is welded. This shape of the pin is necessary for a more rigid installation of the element in the masonry.
If you choose an L-shaped version of the stud or reinforcement, then it will be enough to deepen it into the masonry by three rows, that is, approximately 200 mm. If even studs are installed, it is recommended to embed them at 350-400 mm.
The next step is to lay waterproofing material on the top row of masonry. To ensure that the waterproofing lies evenly on the wall surface, holes are cut in the rolled material where the studs reach the surface.
Next, markings are made on the Mauerlat beam for the holes through which it will be put on the studs. This process can be carried out quite simply, even without a ruler and pencil. To do this, the beam is installed from above, on the protruding studs, and it is tapped from above with a hammer in the areas where the fasteners are located. There should be dents on the beam through which through holes will be drilled. The diameter of the holes must exceed the diameter of the stud by 2÷3 mm so that the beam can be easily put on the fasteners, without distortions.
If the beam is installed on studs that have threads at the top, then a wide washer is put on them and the nut is tightened. If the Mauerlat is mounted on reinforcement, then its free end must be bent at a right angle and secured to the surface of the beam with powerful nails, which are driven in and then bent.

Anchors

This type of fastening is suitable for a power plate that will bear both light and heavy loads. The main difference between anchoring a beam to a wall is that it does not require any preliminary embedded elements.

The anchor fastening consists of two elements - the expansion anchor itself, installed in a hole drilled for it in the wall and timber, and a screw, which is inserted into it, and on which a nut is screwed on top. When the nut is tightened, the screw moves upward progressively, together with the conical head, which moves the “petals” apart and ensures reliable fixation of the fastener.

Installation work on installing the Mauerlat using this method is carried out in the following order:

Waterproofing material is laid on the wall.
The mauerlat beam is laid on top of it.
Next, markings are made along which through holes will be drilled.
The anchors must have a diameter of 10÷15 mm, respectively, the holes are drilled with a drill of 12÷17 mm. The drill must pass through the timber and go deep into the wall by at least 180÷200 mm.
The next step is to drive anchors with a screw part into the holes, onto which a nut is then screwed using a wrench, under which a wide washer is placed.

Fastening the Mauerlat to the reinforcing belt

A reinforcing belt under the rafter system will never be superfluous, even if the walls of the building are strong enough, since attaching the Mauerlat to it is as reliable and durable as possible. For some buildings, a reinforcing belt is simply necessary, for example, this applies to backfill walls or walls built from aerated concrete blocks. Aerated concrete is quite fragile and holds fasteners very poorly on its own.

Creating a reinforcing belt

The reinforcing belt for installing the Mauerlat can be made without help. Of course, if the work is carried out by one person, it will go much slower, but the main thing in this case is the opportunity to save money.

The reinforcing belt is a ribbon of concrete, inside of which there is a metal frame made of reinforcement. The width of the belt should correspond to the width of the wall, its height is 200÷250 mm, and it runs along the entire perimeter of the building. It is very important to ensure that the number of fasteners should be equal to the number of rafter legs. Therefore, having calculated the number of rafters in the roof structure, the pitch of the location of the fastening embedded parts is calculated.

In order for the belt to be strong and not crumble, M400÷500 cement is used to prepare the solution, and the finished concrete from it is poured into the formwork in one go.

The solution for pouring the reinforcing belt is made from cement, crushed stone and sand, in proportions 1: 3: 3. Sometimes plasticizers are added to the mixture, which allow the poured solution to dry evenly and reduce the amount of water used when mixing it.

Briefly, the process of pouring a concrete belt is shown in the table below:

Illustration

Brief description of the operation performed

Illustration	Brief description of the operation performed
The first step to fill the reinforcing belt is to install the formwork. It can be made from different materials. Most often, boards are used to mount this box, and bars are used to fasten them together. This is the most affordable material, which, after the belt hardens, can be removed and reused. It is quite possible to use third grade lumber. To prevent the poured solution from seeping into the gaps between the boards and into the joints between them and the wall, it is necessary to secure dense polyethylene on the inside of the wooden walls, which can be removed after the concrete has hardened.
Another formwork option consists of two layers - plywood with a thickness of at least 10 mm, fixed to the wall from the outside, and insulating material installed from the inside of the structure and pressed against the plywood sides.
It is advisable to install the insulation on the waterproofing sealant, and also use it to glue the corner joints of the material, and then wait for it to dry. Then the solution poured into the formwork will remain completely inside the formwork.
Another option is permanent polystyrene foam formwork. It consists of hollow blocks that are assembled into a single structure, and it is also advisable to fix them on the wall using waterproof sealant. This design is both formwork and a thermal insulation layer, which will reduce the impact of a powerful cold bridge through the concrete belt and will retain heat in the attic. However, it makes sense to use foam blocks or an internal layer of thermal insulation on the formwork if the roofing system itself is fully insulated. Whatever material the formwork is constructed from, its upper edge must be carefully aligned horizontally using a level.
The next step is to assemble the reinforcing structure. Reinforcement is installed along the inner walls of the formwork, along the upper and lower edges, with a distance of 15÷20 mm from the top and bottom.
The reinforcement is tied with thinner wire, and the shape of the frame should generally follow the shape of the internal space of the formwork.
The individual parts of the reinforcement are fastened together with twisted wire.
In order to create the necessary clearance between the internal walls and the reinforcement system, and at the same time the structure is fixed in one position, special clamps are installed on the reinforcement rods.
The star fastener is most often used to create a gap between the formwork wall and the reinforcement, which must be filled with a layer of concrete mortar. The clamps are produced under different numbers, which determine the thickness of the concrete layer that will separate the reinforcement and, in this case, the insulation, and in other cases, the outer edge of the wall or formwork being poured. That is, the reinforcement structure is completely hidden inside the concrete and will be completely safe from corrosion there. The distance can be from 15 to 75 mm. The clamps are installed in increments of 500÷750 mm.
Having finished reinforcing the formwork, studs are installed at a distance equal to the pitch between the rafters, since in this option they are embedded in the belt reinforcing the building. The bottom of the pin should be L-shaped. It is installed on this bend at the bottom of the formwork, in the middle part of the reinforcement structure, and is rigidly fixed with twisted wire in two places - on the horizontal lower and upper lintel. The studs must stand strictly vertically and on the same line, and rise above the future belt by the thickness of the Mauerlat, plus 50÷80 mm.
The next step is to fill the formwork with concrete mortar, the surface of which is leveled along the walls of the box. Leveling the surface of the reinforced belt is done using a rule or a flat board.

After the reinforcing belt has hardened (this process should take at least 15–18 days, or even more depending on its thickness), you can proceed to the installation of the Mauerlat. This process will no longer differ in any way from a similar operation when the studs were embedded in the brickwork.

Video: an original solution to the problem of creating a reinforced belt under the Mauerlat on an aerated concrete wall

Other ways to install mounts for the Mauerlat

In addition to what was mentioned above, there are other ways to fasten studs into the concrete of a reinforced belt for installing a Mauerlat.

log staples

A. Formwork is installed according to the same principle - from boards, plywood or foam permanent blocks. In addition, the walls of the formwork can even be made of ordinary or aerated concrete bricks.

A reinforcement structure is also installed inside the formwork, but the studs are mounted differently before pouring the mortar into the formwork.
The wooden walls of the formwork are fastened together with jumpers, installed at the same distance from each other - it must correspond to the spacing of the rafters. The middle is determined on the slats, and a hole is drilled at the found point with a diameter 2÷2.5 mm larger than the diameter of the pin.
Next, the pin itself is installed in the hole, having a height of 100÷150 mm greater than the height of the belt and Mauerlat. From below, the stud is screwed into a nut - at the point where it rests on the bottom of the formwork, that is, at the end of the wall of the house. Additionally, it is advisable to secure the stud with two nuts on the jumper itself in order to install it strictly vertically. The top nut will then be easy to remove when removing the formwork. All other studs are installed in the same way.
When all the embedded elements are installed, the concrete solution is poured into the formwork and leveled to the level of the walls.

If in this way the studs will be installed in formwork made of brick or aerated concrete, then wooden overlays with a hole for the stud can be simply installed without even securing them to the walls.

The concrete solution in the formwork must harden and gain strength for at least 15 days. Stripping is allowed only after the concrete has gained at least 70–75% of its brand strength.

B. Mauerlat can be anchored to a reinforcing belt in the same way as to walls built from other materials.

B. If it is decided to fix the wooden beam with wire, then it is screwed to the reinforcement, which is prudently installed inside the formwork and protrudes from both sides of the belt.

Waterproofing layer under the Mauerlat

Waterproofing is laid on the end part of the wall or on a concrete belt to preserve the Mauerlat timber from penetration into the wood by capillary action from building structures and, accordingly, to prevent decomposition processes. It is recommended to lay waterproofing over the entire width of the wall, and for a better fit of the material to the wall material, it is fixed to bitumen mastic, which in itself is a good waterproofing agent.

Holes are cut in the waterproofing material if it is mounted on top of embedded studs. The material must stretch, since there should be no folds or gaps between it and the concrete belt.

You need to work with mastic carefully so as not to spoil the outside of the walls, especially if it is not covered with finishing material.

A few words about fastening the rafters to the Mauerlat

As mentioned above, the purpose of the Mauerlat is to evenly distribute the load from the rafter system over the entire surface of the wall. And how it performs its function will determine how the entire roof structure will behave when exposed to additional loads in the form of wind or snow drifts.

There are two ways to fasten the rafters to the Mauerlat - rigid and sliding, and which one to choose primarily depends on which rafter system is chosen for installing the roof - layered or hanging.

Rigid mount

Rigid fastening implies the complete exclusion of displacement of any parts of the system. It is most often used for a gable layered rafter system, which has additional support in the form of a permanent partition inside the building.

To install a rigid structure, several types of fastening are used:

— Support beam and metal corners.

— Cutting the rafter leg into the mauerlat and additional fastening with corners. The cutout in the rafter should not be larger than ⅓ of its width.

— Fixation of the rafter leg using ties and a metal corner.

— Notching using a cutout in the Mauerlat and staples driven into the rafters and Mauerlat.

— Additionally, a notch on a rafter resting against the mauerlat is often secured with nails driven in at an angle.

It should be noted here that if a house is built from a log or timber, the role of the mauerlat is most often performed by the top log, to which the rafter legs are attached.

Sliding mount

Sliding fastening is most often used in a gable hanging system, where the rafters rest only on the external load-bearing walls and do not have additional intermediate support. Sliding elements attached to the rafters and the mauerlat allow the structure to move when the house shrinks or when the effect of external loads on it increases.

This design is especially important for wooden log houses, since after construction shrinkage is inevitable, sometimes reaching up to 15%, and, as a rule, it occurs unevenly.

Deformation processes of the elements of the rafter system can also affect during its operation. So, in rainy times, wood can swell from moisture, since it is quite hygroscopic, and in winter frosts and extreme heat it can dry out.

Sliding fastenings help maintain the integrity of the structure, because when it settles, its individual parts can move along with the wall.

rafter mount

In addition to sliding fastenings of rafter legs to the mauerlat, a hinge made of movable plates can also be installed as a ridge connection. This type of fastening of elements also helps the roof structure remain intact when its geometry changes during periods of shrinkage or other vibrations.

In order for the roof to be reliable in any situation, before installation it is necessary to draw up a drawing and calculate all the parameters. If the process of erecting a rafter system is being carried out for the first time, then the best option would still be to seek help from specialists, since the strength of this structure depends on many nuances that are simply unknown to a beginner due to inexperience.

At the end of the publication - another interesting video - a home master shares his experience of installing a Mauerlat on a monolithic wall.

What is the Mauerlat made of?

There are several ready-made materials in the form of wooden or steel profiles: timber, steel angle, channel, pipe, I-beam. You can assemble a structure from boards by connecting them together. Let's consider each option separately, determine the advantages and disadvantages of each.

Wooden beam

Beams of different sections are used depending on the weight of the roof itself. The minimum cross-section of the Mauerlat is 100x100 mm, the maximum is 200x200 mm

Particular attention should be paid to the type of wood used. The fewer knots, the better; this defect does not work well in tension, forming rather deep cracks

The latter reduce the strength of the material. But it is the Mauerlat, like no other element of the building, that is subject to tensile loads.

Mauerlat made of wooden beams for the roof of a house

Boards fastened together

If the roof is small, the load from it will also be small. It is recommended to save money by installing interconnected boards 50 mm thick instead of timber. Two boards 100 mm wide will create a beam with a section of 100x100 mm. Four boards 200 mm wide - a Mauerlat with a section of 200x200 mm. You can connect with nails, self-tapping screws, bolts (studs).

Mauerlat made of boards fastened together

Steel profile

Metal for the Mauerlat is rarely used. This is expensive, any metal profile is an additional load on the walls, which is not welcome. A pipe is often used, but it acts as an addition to increasing the rigidity of the entire roofing system.

The pipe is passed through the rafter legs, in which through holes are made. The pipe itself must be attached to a wooden beam.

Requirements for this system:

the diameter of the pipe should be 100 mm less than the width of the rafters;
holes in the rafter legs are made strictly along one axis;
The pipe is fastened to the Mauerlat using clamps.

What affects the rafters

Before you start making rafters, you should decide on their type, method of fastening and linear dimensions. Only in this case can you be sure of the strength and safety of the structure.

How do various factors influence the parameters of rafters?

Physical factor Brief description of the effect on rafter parameters

Roof load size

The rafters must withstand snow and wind loads. During calculations, you need to take the actual maximum values of snow cover from the tables of building codes and take into account the strength and wind rose. The data allows you to find out the total load on the roof slope depending on its area and angle of inclination. Next, you can determine the size of the rafters, their number and pitch. In this case, a safety factor must be included. The fact is that lumber does not have stable and uniform strength values; too many unforeseen factors influence these indicators. In most cases, 50×150 mm or 50×200 mm boards are used to make rafter legs.

Roof type

Gable roofs can be layered or hanging. For hanging roofs, you need to make rafters from stronger boards

In this case, the method of fixing the elements to the Mauerlat is taken into account. If a notch is made, then the width of the boards should increase by the amount of the notch. The fact is that cutting in this place automatically reduces the width of the material that takes the load

If you make a cross cut 60 mm long on a 200 mm thick board, then only the remaining width of 140 mm is taken into account. Accordingly, if, when calculating the loads, rafters from 200 mm boards are selected, but during fastening unintended cuts of 60 mm are made, then the width of the blanks for the rafters increases to 260 mm. This remark is made for those who like to abuse various notches and cuts for the persistent areas of the ends of the rafters. Currently, there are many special devices that allow you to firmly fix the rafter in the desired position without filing

The fact is that the cut in this place automatically reduces the width of the material that takes the load. If you make a cross cut 60 mm long on a 200 mm thick board, then only the remaining width of 140 mm is taken into account. Accordingly, if, when calculating the loads, rafters from 200 mm boards are selected, but during fastening unintended cuts of 60 mm are made, then the width of the blanks for the rafters increases to 260 mm. This remark is made for those who like to abuse various notches and cuts for the persistent areas of the ends of the rafters. Currently, there are many special devices that allow you to firmly fix the rafter in the desired position without sawing.

Purpose of the building

For residential buildings, rafters must have a safety margin of at least 1.4 of the design values. For non-residential buildings the coefficient is reduced to 1.2. Conclusion - the size of the rafter boards on houses is larger than on garages and other extensions.

Purpose of attic spaces

Residential attic spaces (attics) must have an insulated roof. The width of the rafters must correspond to the thickness of the insulating layer. At the same time, you need to adjust the pitch between the rafter legs depending on the standard width of the insulation. If in a given climate zone the optimal thickness of roof insulation is 200 mm, then it is recommended to choose the same width for the rafters. Various extensions of narrow rafter legs during roof insulation are not considered the right solution.

This knowledge will help you make the right decisions both during the manufacture of rafters and during their fixation directly on site. Mistakes in the construction of a rafter system are too expensive; you should not be overly self-confident.

Fastening the rafters

There are two ways to secure rafters - rigid and sliding.

Wood can expand under the influence of humidity and high temperatures; to compensate for these changes, a hinged or sliding joint is used. In this case, one of the structural elements can move freely. It is used for layered and hanging rafters. Can be done closed or open.

closed connection
It is made by means of corners attached to the Mauerlat on both sides. Each corner has an eye into which a plate is installed on both sides, attached to the rafters.
An open connection differs from a closed one only in that instead of an eye for attaching a plate, the corner has a bend in the upper part of the vertical shelf.

Hinged fastening is perfect for houses made of wood, which can shrink during use. For brick and concrete buildings, rigid fastening can be used.

Rigid fastening of the Mauerlat is carried out using a combined rafter system, which includes elements of both layered and hanging rafters. All elements are connected and cannot move relative to each other.

Fastening is carried out by notching, followed by fixing the rafter legs with corners or special LK fastenings. The parts are scrolled with self-tapping screws.

fastening with corners occurs on both sides and provides the required rigidity;
fastening with corners without sawing. Such parts have higher shelves and require more screws. The rafter leg rests on the mauerlat from above without a notch;
LK parts are available in various sizes, which allows you to select them to suit the desired thickness of the timber or board. Regardless of the size, the thickness of the fastening is 2 millimeters. This fastening ensures maximum reliability and rigidity of the structure;
installing rafters between two boards eliminates the need for additional metal fasteners. This method is suitable in cases where the required roof slope can be achieved only by slightly raising the rafter leg above the mauerlat. In this case, two boards are installed vertically on the Mauerlat on both sides of the rafters. The elements can be fastened to each other using nails or metal pins.

Attached to the mauerlat, to the floor beams, the rafters are additionally connected to the wall using twisted steel wire, which is secured with a ruff in the masonry. Such an event should be carried out at least through one rafter leg.

When do you need to make moving connections?

Here we come to dynamic support nodes - connections that can change their position. What is it for? Let's remember the physical properties of materials - many of them shrink or swell. First of all, this applies to buildings made of pure wood - timber, logs, etc. Natural wood necessarily shrinks, due to which your roof can not only be deformed, but also completely collapse. To avoid such fatal consequences, craftsmen recommend sliding fastenings of rafter legs with a mauerlat (or the upper crown of a log house).

A prerequisite when installing sliding units is to support the rafter frame on a strong ridge beam. Since the supporting lower nodes are dynamic, maximum rigidity should be achieved at the roof ridge. The upper edges of the rafters are sawed down for a tight connection between themselves and the ridge beam, connected and reinforced with crossbars, metal strips, plates and corners. It is better to connect the rafter element already fixed in the ridge to the crown of the log house.

Requirements for the Mauerlat

The Mauerlat should be made from the same material as the entire rafter system. This means that in the case of rafters made of wood, the base for them should be wooden, and if the roof is mounted from metal, then the best option for the Mauerlat would be an I-beam or channel. It is worth saying that quite often in frame construction a separate beam is not used to fasten the rafters; in this case, the functions of the Mauerlat are taken over by the upper crown of the wall, which is tied to 2-4 underlying logs. Since the roof itself has a lot of weight, the Mauerlat beam should not be too large, but it should cope with its tasks for many years. It has been experimentally established that the optimal solution would be to use timber with a square cross-section with a value of 10 or 15 cm, as well as with a rectangular one - 10x15 cm or 15x8 cm, read more about the dimensions of the Mauerlat. It is not advisable to use round logs, since they will not provide the strongest grip and you will have to put a lot of effort into leveling the bottom. If you still decide to mount the Mauerlat from a log, then you should choose a product with a diameter of 18 cm.

As a rule, the Mauerlat is laid in a continuous row along the walls. However, if the rafters are installed in increments of 150 cm, it is allowed to install the base in segments, that is, under each of the legs

In addition, it is important to take into account the method of installing the rafter system; it is useful to know: methods of attaching the rafters to the Mauerlat. It is customary to distinguish between two options:

sliding installation, in which the rafters rest only slightly on the Mauerlat, and their edge hangs freely; installation is point-blank, that is, the end of the rafters rests against the mauerlat, this fastening resembles a tongue-and-groove lock connection, however, it is important to keep in mind that cuts should be made in the rafters, and not in the mauerlat beam itself, as this can lead to its weakening strength characteristics.

Do not forget about treating wooden surfaces with protective agents against fire, moisture and bugs. In addition, it is necessary to use only high-quality beams that have been dried in the correct way. As for the question of how to attach the Mauerlat, the answer depends on the material used to make the walls of the house. For example, for concrete buildings no additional beam is provided, since such walls can withstand quite high loads

In a wooden building, the upper crown will serve as a mauerlat; of course, it is important to strengthen it and then the walls will cope perfectly with the pressure exerted on them. For panel buildings, a Mauerlat beam is also not required, since a heavy roof is not expected

However, as for brick houses or buildings made of aerated concrete blocks, there are several ways to install the Mauerlat.

Fastening the rafters: all popular methods

Because

The main task of the maueralat is to distribute the loads from the roof; be sure to pay special attention to attaching the rafters to it. The fact is that it depends on whether the roof will move over time, whether it will begin to sag or create stronger loads on one of the walls

This is serious!

There are two technologies for tying rafters to the Mauerlat:

Tough. Here, any displacement of the rafter leg, bends or shifts is completely eliminated. For stability, a hemming block is used, which prevents the rafter leg from slipping. And the metal corners prevent the rafters from moving to the sides.
Sliding. Such fastening is necessary if the house was built from logs or timber, which noticeably settle over time. And the Mauerlat itself is usually not used here - only the upper crown of the log house. If you use a rigid rafter fastening system, then the next year the roof will lose up to 50% of its strength - it will simply fail.

And now about everything in more detail.

Rigid fastening of rafters to the mauerlat

The main task of rigid fastening is to completely eliminate the possibility of rafters moving in any direction. Here the saddle of the cutout on the rafter is rested against the Mauerlat and firmly fixed with nails driven at an angle

But it is extremely important that all such cutouts on the rafters are the same, according to the same pattern and no more than 1/3 of the width of the rafters

The second method is single fastening with a special fastening plate. Additionally, in some cases, a meter-long beam is hemmed under the rafter, which also serves as a stop, and the fastening is done with a metal corner.

Sliding fastening of rafters to the mauerlat

A sliding mount is also called a hinged mount, and for good reason. Keep in mind that different wooden houses shrink differently. So, laminated veneer lumber sags the least over time, and the most is a fresh log house, which drops to 15% in just a year! Moreover, the shrinkage itself always occurs unevenly, which has an even greater impact on the distortion of the entire rafter system - if you have not installed a sliding fastening.

Roof distortion also occurs during the operation of the house itself. Thus, during prolonged rains, wood swells greatly, and in winter it loses a large percentage of moisture and dries out noticeably. Moreover, they settle in completely different ways:

south and north side;
the side that constantly receives moist river or sea air, and the drier side;
the side blown by the winds and the one in front of which there is a utility building;
hidden from the sun by a tree and open.

During all this time, the geometric parameters of the log house are constantly changing. Moreover, even the central wall of the house, on which the racks and beams of the rafter system rest, changes its parameters. Especially during the winter heating period, when it dries out noticeably. Therefore, if the rafters on the mauerlat or the upper crown of the log house are firmly secured, then in winter the snow load will cause the rafter system to bend.

Therefore, the knot needs to be a little loose, for which you will need a fastening element such as a “sled” or “slider”, as people like to call it. This is a special metal part that looks like a loop. When the geometry of the log house naturally changes, it moves along the guide, and the rafters settle a little without any harm to the entire system.

Here's more detail about the process itself:

By the way, some roofers still perform sliding angles using more traditional methods. To do this, they make a cut in the rafter leg, place the beam with a cut on the upper crown and secure it in the following ways:

With staples.
Crossing nails in the mauerlat.
One nail driven vertically.
Stylish fixing plates.

Also, as a good alternative to a modern sliding support, use strong forged wire, twisted twice (we talked about it in the paragraph on attaching the Mauerlat to the wall). It works well in tension and gives a certain degree of freedom to all elements of the roof structure.

As you can see, everything can be sorted out!

krovgid.com

Mauerlat device

Classification of connecting nodes

The roof frame consists of a number of elements, solidly fastened together in the middle. But the main operational load is borne by the rafters, which is why the functional characteristics of the roof and the gas safety of the entire structure depend on the strength of their fastening to the Mauerlat and their connection to each other.

Rafter systems, hanging and layered, transfer the load from their own weight, the weight of the roofing pie and atmospheric influences to load-bearing walls and other structures. The lower ends of the rafters rest on a support beam or Mauerlat, the upper ends are fastened in pairs freely to each other or mounted to the ridge girder. In addition, for the sake of structural rigidity, additional supports, crossbars, struts and other elements are used. If it is necessary to increase the length of the rafters, the rafter legs are multiplied. In general, rafter connection nodes can be divided into a small number of main groups

connection unit with the “foundation” of the roof”; ridge connection unit; fastening unit for additional elements of the rafter system; joining rafters near the extension.

Extension of rafters

Connecting the rafters along the middle allows you to make a rafter leg of the required size from the available lumber. More often, goodbye splicing is performed using the following joining methods

end-to-end; overlap; method of oblique cutting; in three boards; with support on the purlin.

Butt mount

. For splicing, the abutting ends must inevitably be cut off at 90° below the house. After tightly combining the resulting ends, a wooden mask or a metal fastening element (plate with teeth) is mounted on the rafters at the junction. Board overlays are installed on both sides and nailed in a checkerboard pattern with nails of the appropriate length, or fastened with self-tapping screws.

Oblique cut method

. The ends are trimmed under the house at 45°. The cut ends are joined, and then a through hole is drilled in the middle for bolt fastening. The bars are tightened with a bolt with a diameter of 12 or 14 mm with a wide washer.

Overlap fastening

. The wooden elements are laid with an overlap and the entire length of the river is sewn together with nails, which should be staggered. In some cases, studs with nuts and washers can be used. Such a connection of river rafters does not require precise cutting of the ends.

A long rafter leg can be made using three boards and spacers. In this case, one of the boards is laid in the middle of the other two with an overlap of at least a meter and fastened with nails in a checkerboard pattern. Then, wooden spacers equal to the thickness of the middle board are inserted into the empty space in the middle of the outer boards and nailed, to ensure the rigidity of the structure.

The connection of rafters of a length with support on an intermediate cycle is carried out in a small case, sometimes all rafter legs are built up at the same distance from the roof overhang. The horizontal cycle is mounted on racks that rest on the internal load-bearing wall or columns. In the case where the domicile of the splice falls on the purlin, there is the potential to provide the necessary rigidity of the long rafter leg. Both parts of the rafters are connected to each other by staples or other elements, and are also attached to the purlin with nails.

What is the secret of the quality of the rafter system: three main rules of the master

High-quality lumber is half the battle on the path to successful construction. The mauerlat and rafters should not have cracks, wormholes or knots.
The accuracy of measurements, cuts and uniformity of the position of the fasteners is an equally important point. If all the rafter legs are the same length and cross-section, then it is better to prepare a template for making cuts and notches.
Gaps on the Mauerlat – loss of the load-bearing functions of the base by 50% or more. The percentage of strength reduction depends on the depth of the notches.

When the rafter system is ready, it’s time to install the sheathing, insulation and roofing material. But this is another interesting topic, which we will definitely talk about in the next article. In the meantime, we wish you good materials, easy work and good helpers!

How to install the Mauerlat yourself

Let's look at how to do it yourself and mount the Mauerlat correctly. To make the frame, the material from which the elements of the rafter system are made is used.

The material for the Mauerlat can be used:

wood;
steel profile.

It is important to ensure the continuity of the supporting contour and reliable fixation of the joints. In most cases, a reliable roof slat is made from square-section wooden beams with a side size of 15 or 20 cm

It is not advisable to increase the cross-section of the beam, which is associated with additional costs and increased load on load-bearing walls. If the material of the required cross-section is not available, you can make a support beam of a composite structure using boards 5 centimeters thick.

Carry out construction activities for installing the Mauerlat according to the following algorithm:

Clean the supporting surface of the main walls from construction debris and dirt.
Lay two layers of waterproofing material around the perimeter, which can be ordinary roofing felt or polyethylene.

Prerequisite: the Mauerlat must be laid closer to the inner edge of the wall and there must be at least a little protection on the outside

Cut blanks from wooden beams, the length of which corresponds to the size of the walls.
Carry out cutting of corner joints and joints of timber.
Treat the workpieces with antiseptic impregnation and fire-retardant compound.
Mark the coordinates of the holes for fastening the support frame elements, using a flat board attached to the fasteners.
Drill the beam, ensuring that the holes you make are perpendicular to the top and bottom edges.
If necessary, join the beams using an oblique cut, self-tapping screws, nails or bolts.
Secure the corner elements of the resulting frame using plates or staples.
Connect the assembled roof plate to the fasteners and secure according to the chosen fastening method.
Check the horizontal installation of the support frame using a building level.
Install shims, if necessary, to ensure the required position.

Construction of layered rafters: basic rules

A layered rafter system is used when it is necessary to cover spans with a maximum length of 6-6.5 meters. If there are load-bearing structures (walls or columns) in the interior of the building, then it is possible to additionally install racks on them.

One of the most functional parts is the sliding type rafter support, since it can be used to attach various intermediate rafters to the Mauerlat.

Since large spans are very rare in private construction, layered systems are mainly used in individual buildings.

According to technology, the support for the rafter leg is the mauerlat. If we are talking about a wooden building, its function goes to the top row of walls. This nodal connection is of utmost importance.

When tightening the rafter legs using a crossbar, you can increase the span length to 8 meters, with one support - up to 12 meters, with two supports - up to 16 meters.

It is prohibited to lay wooden rafters on stone walls, since condensation will constantly form on them, which will have a destructive effect on the wood. To prevent possible rotting of wooden parts, it is necessary to insulate the Mauerlat. The same rule applies to all areas where wooden elements are adjacent to metal or stone structures.

The first step is to secure the Mauerlat. This part is essentially a beam with parameters 150 x 150, 150 x 200 mm. The process is carried out using pins. They must be concreted into the wall at least 40 cm deep. The bolts are secured in a similar way. For this purpose, twisted wires are used, the minimum diameter of which should be 6 mm. Their laying is carried out at the stage of wall construction no higher than the third row of masonry (counting is carried out from the top row).

Fastening of layered rafters to the Mauerlat can be done using brackets. Similar requirements apply to timber laid on top of external structures - the beam.

When constructing houses, a system of layered rafters based on wood is used. The manufacture and use of such metal parts is impractical and quite problematic.

It is convenient to connect and fasten rafter beams, support beams and other parts using fasteners in the form of teeth, tenons, and frying pans, widely used in carpentry.

One of the most important points is the accurate calculation of the layered rafter system even before the installation of the rafters begins.

Wall mounting methods

Correctly fastening the Mauerlat to the walls will ensure its reliable operation.

Depending on the type of base, attachment points are made in four ways.

Fastening with wire. Method for brick houses. A twist of wire with a diameter of 4–6 millimeters is placed in advance in the masonry at a distance of 5–6 rows from the top. After the masonry mortar has hardened, the wire is threaded through the beam. The ends of the wire are twisted or wrapped around the Mauerlat. The step of such fastening is at least 60 - 70 centimeters; Fastening with anchor bolts. The anchors are laid in advance in a reinforced concrete belt made along the edge of the wall. This method is suitable for relatively soft walls made of concrete blocks. The belt allows you to distribute the concentrated load from the roof even more efficiently. Anchors should be fastened at intervals of at least rafter spacing

It is important to think about the location so that it falls on the spaces between the rafter legs. The Mauerlat is installed on anchors and pulled to the wall

This method provides the most rigid connection possible, but is characterized by the highest cost; Fastening with pins. This type of fastening is suitable for small brick buildings. L-shaped studs are laid in the brickwork with the curved end down. The laying depth is assumed to be at least 45 centimeters. The length of the stud should be selected so that it passes through the Mauerlat and allows fastening with nuts. The cross section of the stud is 12 - 16 millimeters. The waterproofing layer between the wall and the Mauerlat is also pinned onto studs. With this method, the upper layers of the masonry are reinforced with additional reinforcing mesh; Fastening with staples. Wooden blocks are installed into the masonry 2–3 rows below the edge of the wall. The brackets are attached to these bars from below, and to the Mauerlat from above. This method does not damage the waterproofing layer.

If the Mauerlat is installed directly on brickwork or on aerated concrete blocks, a point load will occur. As a result, the wall may collapse. Armopoyas is the solution to this problem.

Fastening to a brick wall without an armored belt

There are several mounting options here. Each of them has its own pros and cons.

Wire fastening

You need wire with a diameter of 4–6 mm, twisted in several layers. It is laid in brickwork as a through element, at a level of 4–6 rows below the installation of the Mauerlat. After laying the Mauerlat on the wall, it is tied with wire from above, pulling it towards the wall end.

It is important to adjust the twisted wires to the correct length. You will have to take into account the height of the brickwork from the place where the wire fasteners were laid, the thickness and width of the Mauerlat, and the length of the twist for tightening (about 15–25 cm). The resulting size is doubled and the width of the wall is added.

An example of fastening a mauerlat beam using wire

The distance between the laid wires is determined in the same way as with anchors. The basic rule is to begin installation after the masonry mortar has dried.

Instead of wire, you can lay small-diameter steel pipes in the brickwork. And then pass the fastening wire through them.

Using Wooden Plugs

Wooden plugs are the same timber of a smaller cross-section, which is cut into small pieces 20–25 cm long. They are laid in brickwork, pre-treated with an antiseptic composition. Here are several options where you can install wooden plugs in the wall:

in the top row in the middle of the wall width;
on the inside of the wall under the mauerlat;
on the inside, under the mauerlat, 1–2 bricks lower.

Usually the Mauerlat is attached to the plugs with metal brackets.

Using pins and wire

It is necessary to prepare studs with a length slightly less than the width of the wall, plus 3 cm as a protrusion beyond the wall structure. It is the protrusion that must be equipped with a thread, washer and nut. The opposite end of the fastener should be bent at 90°.

An example of the correct fastening of a mauerlat beam with studs

The stud is laid in the brickwork in a horizontal position 4–6 rows below the installation level of the mauerlat. The threaded end should come out from the inside. After installing the power plate, a wire folded in several layers (3–4) is wound onto the stud, which is tightened with a washer and nut. The free end is attached to the Mauerlat by any means and methods. There is an option when the Mauerlat is not fastened with wire, but rafter legs are attached, which are pulled up to the Mauerlat, pressing it against the wall. The main task in both the first and second cases is to tighten the wire so that it takes a strictly vertical position and, in terms of the degree of tension, resembles a string .

Fastening with anchors

The technology is somewhat similar to the construction of a Mauerlat using anchors along an armored belt. Here the same anchors are used, which are placed vertically into the brickwork to a depth of 45–50 cm. The lower end is bent at a right angle; it must be placed under the brick, and not in the seam between the bricks.

The main problem is to install the fasteners vertically. Therefore, advice - when assembling brickwork, constantly check the location of the anchor for verticality, using a plumb line or level. A small deviation is a big problem when putting the Mauerlat on fasteners.

Fastening the Mauerlat using anchors to a brick wall

Here, the preparation of wooden beams is also carried out, taking into account the distance between the mounting holes and their drilling.

Attention! All methods used in the technology of installing a Mauerlat without an armored belt are possible only if the differences in the upper ends of the walls are insignificant. If the difference is large (more than 1 cm), then you will have to pour a cement-sand mortar screed over the wall. The thickness of the screed is at least 5 cm.

What materials can it be made from?

The structure is often made of wood, using wooden beams or boards fastened together. Often a steel profile is used. The choice depends on the weight of the roof.

Wooden beam

The timber is placed under the rafters along the perimeter of the roof. With this arrangement, the load is evenly distributed to each point on the walls of the house. There should be no knots on the timber, and if there are any, their size should not exceed 2/3 of the thickness of the wooden product. When arranging the Mauerlat, knots will interfere with the main structure, so it is better to avoid them. If there are many knots on the beam, then a break may occur in the places where they form.

Boards fastened together

In frame construction, when the roof is light in weight, boards fastened together can be used. This design is not suitable for a heavy structure - the boards will not withstand the high load. This material is suitable for roofing without insulation and additional elements that increase weight. The boards are attached around the perimeter of the building. For the Mauerlat, it is advisable to use durable material that will not crack during use and exposure to external factors.

Steel profile

Instead of wooden products, steel structures are often used. This material is more durable, as it can withstand increased loads. The steel profile is represented by a square section or round metal pipes. The use of steel as a support for the roof implies the presence of metal lining around the perimeter of the external walls. The device is suitable for a gable roof, and beams can also be used. The harness is secured to the outside of the wooden belt.

Arrangement of a reinforced belt

After the concrete has hardened, a beam is placed over the rods protruding from the reinforcement. Even on the shortest wall, there must be at least four 12 mm rods in the armored belt for attaching the Mauerlat. When choosing pins or wire, the belt must also be made with reinforcement.

The thickness of concrete when constructing an armored belt cannot be less than 5 centimeters. As soon as the mixture is poured, it is necessary to ensure that air cavities do not form in it, which can be seen by the bubbles that appear.

This process violates the homogeneity and strength characteristics of the armored belt, but it is necessary to lay the mauerlat on it, which in fact is the foundation of the roof. Air bubbles will disappear if you pierce the not yet hardened concrete with a reinforcing bar. After 10 - 12 days, the formwork is removed after the mixture has hardened and become strong.

Next you need to do waterproofing. As an insulating material, roofing felt is laid on the finished armored belt.

What do you need to know about the Mauerlat?

The most commonly used section of the Mauerlat is 250 x 250 mm, 100 x 100 mm - in attics of complex configurations and small architectural forms. There are many options for fixing timber around the perimeter of walls, passing rafters (hanging, layered), and rafter schemes. Mauerlat calculation is not required in the following cases:

increased pitch of the anchors with which the mauerlat is attached to the walls; log structure (the last crown serves as the mauerlat); the beam rests on the protrusion of the brickwork.

Scheme for attaching the Mauerlat to a wall made of blocks.

The cross-section in these cases is taken to be 150 x 150 mm or 100 x 100 mm. The Mauerlat of rectangular cross-section (150 x 100 mm) allows you to adjust the line of the counter-lattice, placing it in a single plane with the plane of the pediment. The technology is in demand under such conditions as:

gable roof; reinforced concrete floors that disrupt the rows of masonry.

Under standard conditions, two forces act on the Mauerlat: the vertical compresses the wood fibers under the weight of the roof, the horizontal bends the beam, tearing it out of the plane of the wall. Both forces are too insignificant for wooden structures. Therefore, the Mauerlat is not calculated, but its cross-section is assigned constructively.

In practice, they take the standard dimensions of the Mauerlat for residential buildings within the range of 250 x 250 mm, 100 x 100 mm, using schemes for connecting the rafters with the Mauerlat without horizontal forces.

Support reactions in the horizontal plane occur only with fixed supports, even when choosing layered rafters. On the other hand, hanging rafters with tightening and movable supports completely eliminate the horizontal reaction of the Mauerlat. In addition, the pitch of the Mauerlat anchors is chosen by builders more often than required, so calculations for bending do not make sense in 99%.

Options for supporting the rafter leg on the mauerlat.

The creators of manuals for builders on wooden structures, Filippov, Meler, Shishkin, agree that:

layered rafters can be designed without transferring thrust forces to the walls; layered rafters can cause thrust forces in the walls of the cottage.

In the first case, the Mauerlat does not require rigid fastening; the roof must have symmetrical slopes and a simple design. In this case, the thickness of the Mauerlat is chosen arbitrarily; it has no design significance. In the second option, the rafter system expands on itself, providing rigidity and structural strength with asymmetrical slopes, their complex configuration, and uneven loads of low-rise buildings.

The procedure for attaching the Mauerlat for a gable roof

To install the Mauerlat on frame or timber walls, screws, self-tapping screws or nails are used. To provide additional strength, perforated connecting parts are used.

If the house has a large area, and the roof will have a size of about 250 “squares”, then to attach the Mauerlat they use studs - threaded metal pins. They are installed every 2 meters and along the edges of the element.

First of all, for the armored belt, a concrete screed is poured around the perimeter of the walls, and then the pins are sequentially embedded so that the height of each of them is at least 3 centimeters greater than the thickness of the Mauerlat. Only after this can the Mauerlat be firmly fixed using nuts and washers.

In addition to them, metal staples are easy to use and are durable. We should not forget about the possibility of using anchors and twisted wire, which have excellent tensile properties.

Builders consider the simplest method of fastening to be using wire rod:

Several rows before the very top of the masonry, pieces of wire are laid out between the brick rows so that their length is sufficient to tie the mauerlat after the walls are finished erecting.
After completing the installation of the connecting element, the remaining ends are hidden between bricks in the thickness of the wall.

Mounting can be done differently:

Reinforcement pins are embedded in the armored belt - they should be located below the height of the Mauerlat.
4-5 centimeter studs or long bolts with cut off heads are welded to them.

There is another method, which involves embedding studs or pins into them while laying the walls. But this option is only suitable for small roofs.

How to make a Mauerlat on your own

To ensure reliable fastening, it is important to mount the beams correctly and ensure a strong connection between the elements. After laying the Mauerlat, you need to secure the roofing structure to it

After laying the Mauerlat, you need to secure the roofing structure to it

Let's consider the sequence of operations for installing a Mauerlat made from a wooden beam with a square profile:

Thoroughly clean the upper surface of the load-bearing walls from debris and mortar buildup.
Lay a double waterproofing layer of polyethylene film or roofing felt.
Cut the support beam into pieces, the total length of which corresponds to the perimeter of the box.
Cut the corner areas of the joint, as well as the end plane in the areas where the timber is built up.
Apply an antiseptic composition to the surface of the wood and treat it with fire-resistant impregnation.
Mark the rafter attachment points using a tape measure or a template in the form of a regular board.
Drill holes in the beam, ensuring they are perpendicular to the supporting surface.
Connect the beams of the support frame using threaded connections, an oblique cut or self-tapping screws.
Reinforce perpendicular beams with metal plates or special brackets.
Attach the roof plate to the upper tier of the main walls using the selected fixation method.
Check that the support structure is positioned correctly and is not distorted using a level.

If necessary, you can use shims to correct minor distortions. It is easy to attach rafter beams to a securely fastened Mauerlat using any of your favorite methods.

Peculiarities

Most often, not solid logs, but beams are taken under the mauerlat. It is more convenient and easier to work with. The beam is ribbed and stable. If you put it on the walls, it won't fall. Mauerlat is very important when constructing a roof, so read the recommendations and select timber of the required diameter. Which one exactly is needed? This depends on various parameters:

The total area of the house and how much is the perimeter of the walls?
Roof type;
The material with which the roof is covered;
The material from which the supporting structures are made;
The climate in the area;
Is there an attic, several or other extensions?

To a greater extent, the calculation will depend on what type of roof you decide to install on your home? In your case it is gable. Start from this when selecting materials for construction.

Types of roofing work

People from non-construction fields always ask questions like “what types of roofing work even exist?” Now I will answer this question.

Roofing is a complex process and there are many individual tasks involved.

Creation of a roof project. At this stage, the appearance and functional purpose of installation of rafter legs is selected. This is a rather labor-intensive and important process, so it can be separated from the entire system

Here it is important to choose the correct location, section and pitch Laying the roofing pie (insulation boards, waterproofing, vapor barrier) Installation of the sheathing. The pitch of its elements depends on the roofing used, for example, when using soft materials, it should be continuous, and, say, for slate it will be quite sparse. Roofing decking Drainage system equipment Installation of dormer windows (for complex roofs)

Mauerlat: what is it, what is it for ↑

In the classic version, the Mauerlat (photo below) is a dried timber or log, fixed on top to the outer walls or an armored belt around the perimeter of the house.

Note: When working with metal trusses, use a channel or I-beam. The Mauerlat of a timber house is nothing more than the last crown, which is especially carefully fixed on the previous ones.

Knowing what a roof plate is, it’s easier to understand why such a “belt” is needed.

It is required:

firstly, to distribute, as evenly as possible, the concentrated load exerted by the rafter legs on the area of the upper frame of the walls. As already noted, this is a kind of foundation for the roof rafters;
secondly, it serves to tie the roof. This is especially true for regions with strong winds.

Attention! Some craftsmen are considering the possibility of erecting a roof without a Mauerlat, especially if it is small. In this case, they fix the rafters directly to the floor beams

But how justified is this?

after all, the matrix provides additional rigidity to the supporting structure;
although the slope reduces the bursting force and windage of the roof, however, the likelihood that it will be blown away by a strong wind nevertheless exists.

With hanging rafters

These are systems in which the rafter legs rest only on the external walls without intermediate supports (load-bearing walls). For gable roofs, the maximum span is 9 meters. When installing a vertical support and a strut system, it can be increased to 14 meters.

The good thing about the hanging type of gable roof rafter system is that in most cases there is no need to install a mauerlat, and this makes the installation of rafter legs easier: there is no need to make cuts, just bevel the boards. To connect the walls and rafters, a lining is used - a wide board, which is attached to studs, nails, bolts, crossbars. With this structure, most of the thrust loads are compensated, the impact on the walls is directed vertically downwards.

Types of rafter systems with hanging rafters for different spans between load-bearing walls

Gable roof rafter system for small houses

There is a cheap version of the rafter system when it is a triangle (photo below). Such a structure is possible if the distance between the external walls is no more than 6 meters. For such a rafter system, you can not make calculations based on the angle of inclination: the ridge must be raised above the tie to a height of at least 1/6 of the span length.

But with this construction, the rafters experience significant bending loads. To compensate for them, either rafters of a larger cross-section are taken or the ridge part is cut in such a way as to partially neutralize them. To give greater rigidity, wooden or metal plates are nailed on both sides at the top, which securely fasten the top of the triangle (also see the picture).

The photo also shows how to extend rafter legs to create a roof overhang. A notch is made, which should extend beyond the line drawn from the inner wall upward. This is necessary to shift the location of the cut and reduce the likelihood of the rafter breaking.

Ridge knot and fastening of rafter legs to the backing board with a simple version of the system

For mansard roofs

An option with the installation of a crossbar - used when organizing a living space under the roof - an attic. In this case, it serves as the basis for lining the ceiling of the room below. For reliable operation of a system of this type, the crossbar cut must be hingeless (rigid). The best option is in a semi-frying pan (see picture below). Otherwise, the roof will become unstable to loads.

Rafter system of a gable roof with a raised tightening and a crossbar insertion unit

Please note that in this scheme there is a Mauerlat, and the rafter legs must extend beyond the walls to increase the stability of the structure. To secure them and dock them with the Mauerlat, a notch is made in the form of a triangle

In this case, with an uneven load on the slopes, the roof will be more stable.

With this scheme, almost the entire load falls on the rafters, so they need to be taken with a larger cross-section. Sometimes the raised puff is reinforced with a pendant. This is necessary to prevent it from sagging if it serves as a support for ceiling cladding materials. If the tie is short, it can be secured in the center on both sides with boards nailed to the nails. With a significant load and length, there may be several such belays. In this case, too, boards and nails are enough.

For large houses

If there is a significant distance between the two outer walls, a headstock and struts are installed. This design has high rigidity, since the loads are compensated.

Gable roof rafter system for a large span and ridge and rafter insertion units

With such a long span (up to 14 meters), it is difficult and expensive to make the tie in one piece, so it is made from two beams. It is connected by a straight or oblique cut (picture below).

Straight and oblique cut for connecting the tie

For reliable joining, the connection point is reinforced with a steel plate mounted on bolts. Its dimensions must be larger than the dimensions of the notch - the outermost bolts are screwed into solid wood at a distance of at least 5 cm from the edge of the notch.

In order for the circuit to work properly, it is necessary to make the struts correctly. They transfer and distribute part of the load from the rafter legs to the tie and provide structural rigidity. Metal pads are used to strengthen connections

Fastening struts for a rafter system with hanging rafters

When assembling a gable roof with hanging rafters, the cross-section of lumber is always larger than in systems with layered rafters: there are fewer load transfer points, therefore each element bears a greater load.

Fasteners

Metal products are used to attach the rafters to the Mauerlat:

nails 150 mm long;
self-tapping screws;
rafter corners;
beam holders;
sliding supports;
serrated plates;
perforated pads;
staples;
bolts, studs with nuts.

It is desirable that the fasteners be galvanized or stainless. Regular one quickly corrodes and breaks down, causing loose connections.

For nails up to 6 mm in diameter, pre-drilling of holes is not required. With a larger cross-section, to prevent the formation of cracks, you need to drill a socket with a size equal to 0.9 of the diameter of the nail. In wooden buildings, as well as in small brick buildings, brackets are used to secure the mauerlat and rafters. Wood is prone to splitting, so it is recommended to pre-drill the holes.

About the types of fastening of rafters to the base

Let's talk about modern fasteners. For the strength and durability of the support units, a variety of metal fasteners are used: beam holders, equilateral, fastening, anchor, reinforced corners, plates, supports, profiles, connectors, anchors, etc. All these parts are made of high-quality metal. For dynamic units (types 1, 2 and 3), sliders, angles and perforated plates are used. For rigid fastening, stationary connectors, anchors and corners are used.

Such fasteners for the rafter system are most often used:

For self-assembly, perforated fasteners are more suitable than others, since they have many holes for self-tapping screws and bolts.

Mauerlat connection along the length

This type of structure requires a large length of timber. Most often, you have to splice wooden blocks together.

There are several connection options:

oblique cut The timber at the joints is sawn obliquely with ends 0.15 of the section height. The length of the connection should not be less than the height of the Mauerlat multiplied by two. The connection point is bolted through and through. This method is perfect for connecting the Mauerlat along the length;
"in the paw." This method is suitable for corner joints. For one beam, the lower part of the joint is cut at a right angle, and for the second, the upper part is cut out. The connection point, as in the previous case, is tightened with a bolt. Right angles do not allow the Mauerlat to move.

How to arrange it correctly?

To construct the Mauerlat, it is necessary to use beams whose cross-section is equal to a third of the thickness of the main wall . Typically, timber with a cross section of 150 or 200 mm is suitable for this. It is not worth taking thicker ones, since this is an additional load on the wall, and it is quite difficult to lift beams of such a cross-section to a greater height.

If the mauerlat beams are joined, then the length of each part should be as large as possible. To illustrate this, the following example can be given: the standard length of any lumber is 6 meters. If the wall on which the rafters will rest is 8 meters long, then for the Mauerlat you need to take two beams of 4 meters each. Using a six-meter beam and a two-meter “sawing” would be a mistake.

Internal structure

From the under-roof space, the roof is a rather complex load-bearing structure, having inclined, vertical and horizontal roof elements. For their manufacture, they mainly use well-dried wooden beams or boards, connecting them in a certain way. Instead of processed parts, natural poles of small diameter can be used.

Rafter system

The main part of the roof is the rafters - long thick pillars, beams or boards knocked together in pairs, connected at their ends at a certain obtuse angle. Depending on the length of these parts, determined primarily by the dimensions of the building over which the roof is built, their minimum cross-section is determined. It is convenient to use a table for this:

Please note that the cross-section of the rafters or boards depends on the distance at which they are spaced from each other. An increase in the installation step of the pillars leads to an increase in the load on each leg, which requires an increase in its cross-sectional size. The supporting ends of the rafter beams must lie securely on the walls of the pre-built box

There is also a certain complexity of installation here. Excessive load on the walls can lead to their destruction, so it is necessary to carry out preliminary calculations of this parameter and compensate for them

The supporting ends of the rafter beams must rest securely on the walls of the pre-built box. There is also a certain complexity of installation here. Excessive load on the walls can lead to their destruction, so it is necessary to carry out preliminary calculations of this parameter and compensate for them.

Tightening, rack and struts

A simple way to reduce the pressure of the supporting ends of the rafters is to install a special tie between them - a tie, which is a long beam, post or boards nailed together, to which the lower parts of the beveled parts are attached. This option is possible only in one case - in the manufacture of an unused under-roof space - an attic.

Strengthening the triangle of rafter posts and tie beams is achieved by installing internal vertical and inclined parts. The short insert connecting the junction point of the rafters and the horizontal part of the truss is called a post. Small-diameter posts or cuttings of boards resting on inclined boards are called struts.

Rigel and Mauerlat

More often, when constructing residential buildings, they try to make maximum use of all parts of the building. Residential or utility rooms called attics are made under the roofs. The presence of ties between the supporting ends of the rafter pairs will complicate their use. In this case, another element – a crossbar – helps to strengthen the strength of trusses made of timber or boards.

It is a tie that has smaller dimensions compared to the tie and is installed in the upper part of the trusses. Crossbars are made from scraps of boards or timber with a thickness of at least 50 mm, nailing them in pairs on each side of the rafters. The use of through threaded rods or long bolts helps ensure high strength of the connection between parts.

Sometimes the process of attaching the lower ends of the rafter poles is problematic. In this case, another roof element is used, called a Mauerlat.

Attaching the rafters to the mauerlat

It consists of pillars, boards or timber, laid and secured at the top of the walls. The Mauerlat plays the role of a support and can be located along the entire length of the walls or placed only under the rafters. In this case, the dimensions of the pillars do not exceed 500 mm.

In general, roof installation is a complex and responsible process. A well-made roof can protect the entire structure; errors during its installation can lead to the destruction of the entire structure and significant costs.

Mauerlat manufacturing materials

The Mauerlat can be made from wooden beams, boards, logs, as well as from metal profiles - channel, pipe, I-beam.

Most often, the Mauerlat is made of timber. Its cross-sectional size to a certain extent depends on the size, and therefore the weight of the future roofing system, as well as on the size of the rafter legs.

However, given that the Mauerlat must be firmly laid along the end of the wall, distributing the load, the concealing or bending stresses in it are small, and the wood copes well with compression loads. Therefore, in most cases, the mauerlat does not require complex calculations of the section, and beams with sides that are multiples of 50, starting from 100×100, are usually used.

The table below shows the cross-sectional sizes of lumber most often used in the construction of roof structures in individual construction.

Table of sizes of wooden elements of the rafter system:

Elements of the rafter system

Lumber cross-section, mm

Elements of the rafter system	Lumber cross-section, mm
Mauerlat	Timber 100×100, 100×150, 150×150, and sometimes more.
Rafter legs	Board or timber 60×150, 80×150, 100×200 – based on calculation results
Runs	Beam 100×100, 100×150, 100×200.
Tightenings (crossbars)	Board 50×100, 50×150.
Racks	Beam 100×100, 150×150.
Struts, fillies, cornice box board	Board 50×100.
Wind end and hem boards	Board 20×100, 25×150.

The timber for the mauerlat must be selected carefully, paying attention to its evenness and integrity. It is not worth purchasing deformed, deformed lumber even for the sake of economy, since it will be more difficult to install it on flat wall surfaces without creating internal stresses in it. The wood should not have deep or wide cracks or knots.

Knots are dangerous not only because they differ from all wood in their density and the release of resin from them, as many people think, but also because they significantly weaken the timber. In addition, if a rafter fastening gets on a knot, it will be more difficult to screw a fastener into it or drive a bracket into it, and besides, they will not hold well in such a wood structure.

Boards fastened together are used for lighter rafter systems that do not have an insulating “pie”, for example, when building a country summer house. For this version of the Mauerlat, for example, boards 30÷50 mm thick, laid in one or two layers, are suitable.
Mauerlat is rarely made from metal elements, but profiles are sometimes used for combined options, which include both wood and metal.

When using this option, the load from the rafters is distributed not only onto the wood, but also onto the pipe laid on top of the beam through wooden inserts and pulled to the Mauerlat with clamps. When choosing pipes to reinforce the Mauerlat, you must adhere to some selection criteria:

- since the pipes will be passed through through holes in the lower part of the rafters, they should not have too large a diameter - 40÷50 mm is enough.

— you only need to take a new pipe, and before installation it must be coated with anti-corrosion paint.

Holes in the rafters for the passage of pipes must be made at a distance of approximately 100÷120 mm from their lower edge.

Cutouts are made in the wooden mauerlat, into the bottom of which the end side of the rafter leg will rest. Sometimes on the Mauerlat board, holes for installing rafters are formed by fastening pieces of timber 80÷100 mm high at a certain distance from each other. The width between the installed sections of the bars must exceed the thickness of the rafters by approximately 8÷10 mm, so that it fits freely into the prepared gap.

Due to the fact that the rafters will not be rigidly fixed to the Mauerlat, but installed on sliding fastenings, the system will be able to move slightly when the structure shrinks.

This diagram shows an option using a combined version of the Mauerlat, consisting of a wooden beam and a pipe extending beyond the load-bearing walls along their length. This design feature allows you to immediately make the basis for a protective canopy on the gable part of the roof.

What is a Mauerlat and why is it needed?

Mauerlat is a wooden beam that is laid on the inner surface of the outer wall. A log can be used as a Mauerlat, and with a metal roof frame, a channel or I-beam can be used.

The Mauerlat performs two functions. Firstly, it evenly distributes the load from the rafters over the entire horizontal surface of the wall. Secondly, it provides a connection between the rafter system and the walls of the building. The structural element provides spatial rigidity of the entire rafter system, connecting the rafters to each other.

Mauerlat can be of several types:

solid wooden beam with a cross-section of at least 100 by 100 millimeters;
wooden board, reinforced in places where the rafters support with additional pads;
intermittent mauerlat, the timber is laid only directly in the places where the rafters support with allowances.

Mauerlat is necessary in houses built from small-sized materials such as brick, ceramic stone, concrete blocks. In houses made of logs or timber, the mauerlat may be the last element of the wall, which must be firmly secured to the previous ones.

In frame houses there is no need for this element.

A brick wall and wood have different thermal conductivities and, as a result, different temperatures. Condensation can form at their junction, which causes wood to rot. To avoid this, waterproofing is necessary; an intermediate layer is provided between the Mauerlat and the wall made of roofing felt, linochrome or other waterproofing materials.

Complex roofs

Multi-gable, hip, half-hip or dome roofs are more difficult to calculate and build. The frame is a complex system consisting of parts:

Mauerlat;
main, slanted (diagonal), shortened rafters;
racks;
struts;
runs;
trusses.

In half-hip roofs, the gable section rests on a horizontal reinforced board. If the slopes are connected at an internal angle, there are grooves or valleys. The structural elements are fastened together with a notch and additionally with hardware. If you don’t have enough experience, you shouldn’t take on the installation of such roofs, even if you have a detailed project on hand.

Useful tips

Filling the armored belt is required if the roof area is more than 250 m2. In some cases, however, you can replace it with a concrete beam. Studs are immediately inserted into this beam and placed vertically. The thread of the studs is usually M12. There must be a gap of at least 2 meters between the installation points of the studs; at the same time, they are also attached near the ends, so you can count from the corresponding points.

For medium-sized roofs, pouring the beam is not necessary. Its absence is fully compensated by the use of moderately long hairpins. When arranging the Mauerlat using wire rod, you must plaster it so that the wire does not spoil the appearance. This solution is suitable for roofs of limited size.

You can see one of the ways to attach the Mauerlat in the following video.

Video description

The video shows the technology of attaching the Mauerlat to the wall of a building using anchors:

Chemical anchors

Just recently, no one knew about this fastening technology. Although many craftsmen know how to secure any steel pin using epoxy. The technology is the same here, but instead of epoxy resin with a fixer, other ready-made compounds are used.

One of the methods is called capsule or apmul technology. This is a capsule in which the adhesive composition is sealed. It is driven into the prepared hole, where a pin is driven from above. The first one bursts, the glue spreads inside between the walls of the hole and the thread of the stud. After polymerization, which can take up to 45 minutes, a very strong mount is obtained.

The second option is a two-component composition in cans. A pistol nozzle is put on the latter, with the help of which the composition is fed into the drilled hole. The composition is a polymer mass, quite viscous. Therefore, the anchor will have to be screwed into the filled hole, rather than driven in.

Chemical plug-in ampoule Source homius.ru

Nodal connections of the roof frame

The main key element of the entire frame is the Mauerlat. It is made from a thick beam with a cross-section of 15x15 cm and is laid parallel to the ridge on the axes of the walls. Subsequently, the rafter legs will rest on it. The main task of the Mauerlat is to redistribute the mass of wooden structures (rafters and sheathing), roofing pie and finishing coating onto the load-bearing walls and foundation of the main building. In addition, it will bear the main load from wind and precipitation. In this regard, the fastening of the Mauerlat to load-bearing walls should be as strong as possible.

There are 2 ways to fix the Mauerlat on the walls:

Along the perimeter of a large building, a reinforcing belt is poured in the upper part of the walls. Metal studs with M12 threads are installed into it every 2 meters. Subsequently, the Mauerlat will be placed on these studs and tightened with washers and nuts. If the house is small, then the Mauerlat beam may not be laid at all. The rafter legs will be attached directly to the studs embedded in the wall.
A fairly reliable connection can be obtained if you use steel wire. The middle of the wire is placed under the bricks 3 rows before the end of the masonry. The length of the wire should be enough to firmly pull the Mauerlat to the wall. As in the first case, the rafters can be secured in this way without laying the Mauerlat beam. However, this will create a point load on the walls, which can have a detrimental effect on their integrity.

The pattern of fastening the rafters to the Mauerlat beam can be sliding or rigid. In this case, everything will depend on the type of rafter structure (hanging or layered), as well as the shape of the roof.

Preparing to create a reinforced belt

Its thickness is calculated taking into account the projected loads acting on the roof of the building. They can be permanent (the weight of the rafter structure and roofing pie) and temporary (wind and snow). In any case, the width of the reinforced belt cannot be less than this parameter near the walls.

To get a strong belt, you need to use cement grade M400 and higher. It should be filled in one go. To prepare the mixture, take cement, pre-washed sand and crushed stone in a ratio of 1:3:3. Plasticizers are used as additives to reduce the water content in the solution and, as a result, increase the strength of the armored belt.

It is important that this element is laid continuously on both sides of the external walls of the building. The formwork for it can be building blocks that have a U-shape. Also, to complete the outer row, sawn blocks with a width of up to 10 centimeters are used. You can build formwork from OSB boards and even use standard wooden boards.