During the construction of buildings, upon completion of all construction, installation and external finishing work, a blind area is made along the entire perimeter of the facility.
It is an integral part of the house, reducing the load on the foundation waterproofing systems.
Its construction is strictly regulated by state construction acts, depending on the capital of the building and the type of soil at the construction site.
The only objects that are not required to install such a protective structure are buildings on pile-screw foundations. Although they can be installed there, they only serve a decorative role.
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The underlying layer serves to create a level base and distribute the load. It can be made of sand, crushed stone, clay. Which material to choose depends on the material of the decorative coating. For a concrete blind area, an underlying layer of crushed stone and sand is arranged with separating layers of geotextile.
The top covering is made of concrete or piece materials (tiles, paving stones).
The thickness of the underlying layers under the concrete blind area is 10–20 cm, the thickness of the concrete blind area is from 10 cm. Moreover, taking into account the slope, a meter-wide blind area will have a thickness of 10 cm at the thin edge, and 13–15 cm near the wall.
How to arrange a concrete blind area?
The production of a concrete blind area includes several stages.
What is it needed for, what purposes does it serve, its functions?
What is the purpose of the blind area, why and for what purposes is it installed? It serves as a special, decorative coating made from a variety of building materials. Placed directly under the slope .
It has high insulating properties and is hermetically connected to the outer basement surface or foundation of the house. The outer surface of the structure prevents precipitation from reaching the elements of the base and foundation located below the “0” mark. This design is also necessary to protect the soil from swelling.
The blind area
is being built to solve the following important problems:
- preservation of the base from exposure to precipitation;
- guarantees of foundation integrity;
- auxiliary thermal insulation of the underground room;
- protection of soil from freezing;
- protecting the foundation of the house from deformation of the tree root system;
- minimizing the owner’s expenses for repair and restoration work on the foundation;
- prevention of soil heaving;
- effective removal of climatic precipitation into the drainage system.
Preliminary work
Before constructing the blind area, the following preliminary work is carried out:
- Make markings. Pegs are driven into the corners of the building and the height of the blind area along the base is marked. Having retreated the width of the blind area, drive in the second row of pegs and mark the height of the outer edge of the blind area (minimum 10 cm). Pull the cord.
- They remove the soil around the house to the depth of the underlying layers. It is important to remove all the roots of the plants so that they do not try to germinate later.
- The bottom of the trench is compacted.
- The formwork is installed so that its upper edges protrude beyond the ground level by at least 80–100 mm.
- Layers of sand and crushed stone are poured. Each layer must be compacted. The layers are poured immediately with the design slope. Geotextiles are laid between layers of sand and crushed stone. The minimum thickness of the underlying layers is 10 cm.
- Lay insulation from extruded polystyrene foam in a layer of 10 cm. It is better not to ignore this step, since the insulated blind area protects the foundation from cracking and allows you to reduce the cost of heating the house. Having spent once on insulation, you can save on heating for years in the future.
- Spread a film for cut-off waterproofing, for example, from a greenhouse polyethylene film in two layers. It is laid with an approach to the wall 10 cm above the upper edge of the future blind area so that moisture from the concrete mixture does not go into the sand after laying.
What it is?
First, let's define the construction term. A blind area is a waterproof building adjoining covering made with a slope along the perimeter of the building.
Together with the thermal protection system, waterproofing and drainage, it protects the base and foundation from natural moisture. In addition, it qualitatively performs the role of a transport road structure and is an excellent element of the overall design of the territory of private housing construction.
Requirements for the arrangement of a blind area are laid down in various regulations , the main ones of which relate to the implementation of foundation projects according to SNiP 2.02.01, published in 1983, and the rules for improvement according to SP 82.13330, issued in 2016.
On the territory of the Russian Federation, the construction of residential buildings must be carried out in accordance with approved projects, which specify the type and size of the pie for arrangement of the territory near the base.
The procedure for implementing the protective structure is indicated in the “Working Documentation” . The main requirements that are regulated are:
- design,
- width,
- height and angle of inclination.
Photo of the blind area around the building:
Expansion seams
The concrete blind area is a monolithic slab of quite large size. During the process of gaining strength, stresses will inevitably arise in the material, which can lead to cracking.
One way to reduce such risks is to reinforce the blind area with steel mesh or equally effective and more cost-effective volumetric fiber reinforcement, but expansion joints cannot be avoided. They are arranged across the width of the blind area every 2–2.5 m. To do this, install ordinary boards 15–20 mm thick, placed on edge.
In addition, you need to take into account that the blind area is a structure that is operated in the open air, which means that it will inevitably experience the effects of temperature changes. As we remember from the physics course, a physical body expands when heated and contracts when cooled. For such a large structure as a blind area, these differences can be quite large. This means that the concrete will put pressure on the base, which can lead to its cracking. That is why expansion joints along the perimeter of the base cannot be avoided. They are also arranged using regular boards installed on edge. At the junction of the blind area with the wall, a damper tape made of foamed polyethylene is installed. Subsequently, the boards will need to be removed and the seams covered with sand or filled with sealant.
Pie
It is made in the form of various layers of bulk material and clay. Their volume and layer size are determined by the type of soil, the chosen design and the external cladding of the blind area:
- brick,
- concrete,
- asphalt,
- clay or hard surface with natural or artificial paving stones.
The first layer in the trench is the native soil; it is better if compacted, non-heaving clay is used as the base. Then waterproofing material is laid and then a sand layer up to 100-150 mm, then geotextiles are placed again and a pressure strip is installed. After that, gravel is poured in a layer of 100 to 150 mm and again sand up to 80 mm for laying paving slabs.
When making a pie for a hard blind area,
after the crushed stone layer, formwork with reinforced mesh is made , transverse boards are laid every 2 m to create expansion joints and filled with a concrete layer up to 100 mm.
For heaving soils, an additional layer of thermal insulation is installed as close to the soil surface as possible. Read more here.
Reinforcement of the blind area
Let's return briefly to such an important topic as blind area reinforcement.
It is usually recommended to do this if the blind area is built on weak, heaving soil in order to prevent cracking of the concrete slab.
For reinforcement, a steel mesh with a cell size of 10 cm and a thickness of 5 mm is used, which is laid overlapping. This is a rather labor-intensive operation; in addition, purchasing a mesh is an additional expense.
A much more profitable, less labor-intensive, inexpensive, but reliable option is volumetric reinforcement with polypropylene or basalt fiber. Fiber is simply added to a concrete mixture or mortar, it disperses easily and evenly, providing increased strength, durability, reduced abrasion, increased impact strength of concrete, and also prevents cracking.
We advise you to study: To replace fittings
External covering
First of all, it must meet the following necessary requirements:
- Wear resistance.
- Frost resistance.
- Resistant to leakage and damage from water.
There are several types of external coatings:
- Concrete coating: is rightfully considered one of the most reliable and durable.
- Asphalt concrete: also very reliable, the only drawback is that it requires special equipment to lay it.
- Paving stones, paving slabs: Today, in order to make a blind area for a house, there is a huge selection of paving stones and paving slabs on the market. These types of blind areas have many different shapes and colors, so you can safely choose according to your taste and style. The only precondition is also the thickness of the material; it must be at least 6 cm in order to withstand harsh operating conditions. There are also other types of coatings. We have already briefly mentioned them, or rather types, at the beginning of the article.
Concrete laying
When all the preparatory work is completed, the concrete mixture is placed into the formwork in compliance with the design slope. For better results, use vibration treatment or use special additives for concrete, but more on that later.
Important!
Concrete hardening should occur at a temperature of 18–22°C, taking into account nighttime temperature drops. At a minimum, during the first days after laying the concrete, approximately this temperature should be provided.
Care of the blind area
It is no secret that the strength of concrete depends not only on its composition, but also on the conditions under which hardening occurs.
The laid concrete must be protected from the sun, precipitation, and drafts; A canopy made of polyethylene film is suitable for these purposes.
Hardening processes are most active in the first hours after installation. After 2–3 hours, the concrete will set and will no longer be pressed through with your fingers. At this moment, you need to cover it with a soft cloth and pour water from a watering can. This procedure must be repeated for the first 2-3 days after installation to maintain the optimal moisture content required for hydration reactions in the mixture to occur. Otherwise, the edges of the slab will dry out, and this will lead to a decrease in the strength of the blind area.
Step-by-step description of construction technology
The construction begins with markings, initially setting the width from the walls along the perimeter of the object. After that, excavation work is carried out to construct a trench with the designed depth.
For the reliability of the structure, it will be necessary to correctly install all the necessary engineering support for the structure:
- creation of a drainage system,
- laying waterproofing,
- installation of rainwater inlets,
- gutters,
- curbs,
- correct reinforcement.
This article will tell you how to make a blind area around a house from concrete and other materials on a slope with your own hands. Read about the construction of a blind area around the bathhouse here, around the garage - here, near a wooden house - here.
Creating drainage
With its help, it is possible not only to guarantee dry air conditions in underground spaces, but also to increase the period of operation of the building.
The drainage system of the blind area is mandatory in the following cases: the house is located in a lowland, with a high content of groundwater, clayey and heaving soils, when the foundation is located below the freezing level of the soil, when choosing a non-monolithic structure made of brick, pieces of stone or paving slabs.
Algorithm for implementing the blind area drainage system:
- A trench is made at the level of the greatest rise of bottom waters.
- The bottom is covered with a sand layer and fixed with a geotextile layer.
- A layer of crushed stone is laid into which the perforated pipe is completely installed.
- The structure is wrapped with the remaining parts of the geotextile.
- A layer of sand is poured on top, and then the selected version of the pie continues to be filled.
Read about creating drainage in a blind area here; you can find out which geotextiles are best to use here.
Installation of storm water inlets
The installation of such a structure is mandatory for any house and blind area; it helps remove rain moisture from the roof, preventing it from filling the blind area.
The structure of rainwater inlets is very simple, they consist of:
- square or round tank,
- decorative lattice,
- sand trap siphon.
The most popular products today are made from PVC materials; asbestos cement, ceramics and cast iron products are less commonly used.
The storm inlet is completely deepened into the sand cushion in accordance with the manufacturer’s practical guidelines and its area is filled with concrete mortar. Next, a trench is made from it to install plastic pipes to drain excess roofing atmospheric moisture into the drainage.
Read about installing storm drains and storm water inlets here, and about draining water from the blind area here.
Laying waterproofing
In order for the blind area to cope with the function of water protection, it will need to be waterproofed. In the retail chain you can purchase insulating material for blind areas in the form of rolls, mastic or penetrating insulation.
Algorithm for performing roll waterproofing:
- A layer of non-heaving clay is placed on the compacted native soil of the trench and compacted thoroughly.
- Rolled waterproofing is divided into fragments of the required length with the calculation of making overlapping connections.
- The rolled clay is covered with a waterproofing material with an overlap on the basement wall.
- For the greatest guarantee, a number of such layers are laid, each of which is lubricated with a layer of bitumen solution.
- All layers are individually rolled using a soft-lined roller weighing more than 70 kg.
- The crushed stone layer is filled in and then the remaining layers are made according to the accepted version of the protective structure.
Read about blind area waterproofing here.
Insulation
Blind areas on clayey and especially heaving soils must be insulated to prevent the soil from freezing under the foundation of the house.
Sand of normal size fractions is used as a cushion for thermal insulation , laid in layers from 50 to 100 mm, with moistening and compaction.
XPS slabs are placed on top of the sand layer, close to the insulated surface of the foundation plinth, aligning their L-shaped edges. In this version of insulating the protective structure, fasteners and glue are not required - the slabs are laid in a free position, while ensuring the reliability of the joints, ensuring the tightness of the thermal protection.
Read about insulating the blind area here.
Reinforcement
Most often, to strengthen the structure of a rigid blind area, mesh of various sizes is used. The most popular cells: 50, 100 and 150 mm .
Metal reinforcing mesh is made from wire of different diameters in heavy and light configurations. The first is made of wire with a thickness of 11 mm, and the second is no more than 6 mm.
For concrete blind areas, a heavy type of mesh is used. The structural elements of the mesh are welded in production at the points of contact. In this case, it is allowed to arrange the reinforcement longitudinally, transversely, or combined with a longitudinal-transverse option.
The type of honeycomb is most often made in the form of squares , in the rarest versions - a hexagon or with another configuration. Laying the reinforcing mesh is carried out after installing the formwork on the crushed stone base of the pie.
You can learn about blind area reinforcement from this article.
Gutters
Do I need to install gutters? The gutter is designed to prevent excessive wetting of the adjacent soil due to the flow of atmospheric moisture from the roof. This must be taken into account when creating the level and height of the blind area, otherwise the ribs of the gutters will not coincide with its surface and will interfere with the outflow of water.
Algorithm for arranging a blind area drainage:
- a trench 300 m wide and 150 mm deep is created along the edge;
- the bottom is covered with a sand layer and compacted;
- the formwork must be made with a slope of at least 1.5-2 cm;
- gutters are placed tightly to the blind area;
- pour the structure with concrete;
- after 12 hours, the formwork is removed.
Curbs
Unlike most reinforced concrete products, which are used in the ground, curbs are not waterproofed.
They are installed for rigid and semi-rigid blind areas without formwork. There are certain features of their installation.
So on straight sections they are laid end to end, and on sharp turns, on the contrary, their ends are cut off at two adjacent parts to ensure an exact match of the junction. Read more here.
Expansion joints
When heated by sunlight, this structure begins to expand, so special joints are installed in the concrete layer to prevent thermal cracks from forming.
To do this, distribute the monolithic structure of the blind area into separate blocks. After laying the reinforcing mesh, dividing boards are installed and fixed on it every 2 m and in the corners.
Read here what expansion joints in a blind area are and how they are made.
The device of the junction to the plinth
At the point of such a junction, an expansion joint is installed in the form of a special strip between the base and the blind area made of special plastic building materials, for example roofing felt. It is able to protect the base from pressure from the blind area during the period of soil heaving.
Algorithm for forming an expansion joint:
- The base surface, the size of the blind area trench, is cleaned of dirt.
- A layer of 2 mm bitumen mastic is placed on the prepared surface.
- The mastic is covered with several layers of roofing material.
- After drying, construction work on the blind area continues for 24 hours.
How to make a blind area more durable: secrets of professionals
Have you ever thought about why professionals do things better than amateurs? Of course, experience matters, but you can’t do without “secret tricks.”
One of these life hacks is the use of special additives for concrete, which allow you to give special properties to concrete mixtures.
To make a blind area, it is necessary to use the CemAqua additive, which will ensure high water resistance of the solution, increase frost resistance, do not cause corrosion of the reinforcement metal, and at the same time it is an effective plasticizer of the mixtures.
We also recommend considering an additive such as Plastix from CEMMIX. This is a plasticizer used to increase the mobility of the concrete mixture and increase the strength of concrete.
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Universal polypropylene reinforcing fiber for adding to the solution.
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The addition of these plasticizers helps prevent delamination of the concrete mixture and also increases its mobility, so that concrete can be laid with high quality without vibration treatment.
In addition, plasticizers can reduce the water requirement of the mixture by 10–20% and reduce the amount of cement in it without loss of strength by at least 10%.
As a result, given the low consumption of plasticizer, it comes out free.
Due to the fact that CemAqua and Plastix are supplied in liquid form, packaged in 10-liter canisters, it is easy and convenient to dose and add to concrete mixtures.
After gaining strength, the concrete blind area must be treated with CemAquaStop - a complex moisture-repellent surface treatment agent. The water repellent eliminates the appearance of efflorescence, increases the durability of the surface, virtually eliminates its damage by fungi and mold, eliminates soaking and water absorption in the direct contact of moisture, without reducing the vapor permeability of the surface (the material “breathes”). As a result of using “CemAquaStop”, a very thin hydrophobic coating is formed on the surface of the material - an invisible layer of polymer, which, when exposed to moisture, closes the pores of the material and prevents water from penetrating inside. After treating the blind area with a water repellent, the frost resistance and durability of the treated material increases several times.
The use of modern materials when concreting a blind area allows us to produce a high-quality and durable product, which ultimately saves money, time and effort. The CemAqua and Plastix plasticizers, as well as the CemAquaStop water repellent, can be purchased in Leroy Merlin stores, online stores, and also wholesale from the manufacturer.
You can buy CemPlast, CemBase CEMMIX without leaving your home, with discounts from 5 to 33%!!!!
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Purpose and functionality
As already written above, the main purpose of the blind area is to protect the foundation from moisture from the external environment. In addition, this design performs a number of other important functions, which can be formulated as follows:
- improves the temperature conditions for the use of basements, which is achieved through the use of thermal insulation materials in its manufacture;
- protects the base of the building from excessive waterlogging, thereby increasing the service life of building structures;
- prevents the destruction of the foundation, which can occur when water freezes in winter;
- ensures the drainage of storm water into the sewerage system;
- can be used as pedestrian paths, facilitating cleaning of the local area;
- improves the visual perception of the building, giving it a complete and harmonious appearance.
The wide structure will not only ensure the drainage of storm water and decorate the local area, but will also serve as a pedestrian path
Important! In order to produce a blind area that meets all the requirements for it, it is necessary to follow the technology for performing the work and use high-quality materials.
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Hyperplasticizer
Hyperplasticizers are a new type of plasticizing additives for concrete, ensuring the mobility of the mixture above P5. In addition to plasticity, they increase the water resistance and frost resistance of concrete by 2-3 times.
