Blind area - device, technology and main stages of work

The quality of the various constituent elements of the house largely depends on the structures that are directly adjacent to them and perform a number of inconspicuous, but very important functions.

The blind area is a strip of various materials located around the entire perimeter of the building and adjacent at a certain angle to its walls. The service life of the foundation and the general microclimate in the basement and basement floors depend on the quality of the erected blind area.

In this article, we will try to consider the general arrangement of the blind area and the phased process of its arrangement.

Why is the essence of construction needed

Blind area - device and construction technology

The blind area, as mentioned above, is important and performs a number of functions:

• Protection of the foundation from moisture, rainfall and groundwater;
• Affects the microclimate in the basement and basement;
• Does not give a subsidence of the foundation along the perimeter of the building;
• Decorative element;
• In some cases, it serves as a house sidewalk.

As a rule, the arrangement begins after or in the process of facing the walls and the basement of the supporting base. This process should not be postponed for some time, because after a few years, especially in areas with a high degree of precipitation, flooding of the foundation can significantly reduce its strength.

In the absence of a blind area, in winter and during the cold season, due to freezing of the soil, the soil swells and presses on the concrete base and walls. Subsequently, this leads to the appearance of cracks or the destruction of the supporting structure.

General design and components

The device of any foundation blind area is a "construction cake", consisting of at least two layers: the underlying layer and the outer coating.

1. The base or underlying layer is a compacted material laid out on the ground or waterproofing. For the base, both ordinary sand or gravel, and clay, which will serve as additional insulation, can be used. As a rule, the thickness of the underlying layer does not exceed 30-40 cm. The material is taken depending on the coating used.
2. The outer coating is a material that prevents the penetration of moisture into the blind area and prevents it from being washed away. For this, a concrete-cement screed with the addition of gravel, asphalt or paving slabs is usually used. The thickness of this layer should be at least 10 cm.

Required width and slope of the structure

Diagram of the device with the required width and slope of the surface

The width of the blind area, first of all, depends on the distance to which the edge of the roof of the building protrudes. The minimum required width is in the range from 60 to 80 cm and depends on the type of soil on which the structure will be built.

For stable soil types, the width should not extend beyond the edge of the roof extension by more than 20-30 cm. If the soil layer is unstable, then the width can be increased to 90-120 cm. Further increase practically does not play any role.

General scheme of arrangement

If the blind area also serves as a footpath, then its width may well be 1.5-2m. The main thing is to monitor the overall composition of the building so that the dimensions of the structure are in harmony with other elements of the building.

The slope depends on the coating that is used for the outer layer. For most concrete structures, a slope of 4-5% is sufficient. For a blind area of ​​crushed stone or gravel, it is recommended to make a slope of at least 5-7%.

Device and technology of work

The general blind area can be reduced to the following main steps:

• At the first stage, it is necessary to excavate the soil to the width and depth of the future blind area. It is recommended to treat the dug trench with special means for removing plant roots.
• Along the perimeter of the trench, formwork from a wide board is installed. Small concrete blocks or curbstones can be used as formwork.
• A layer of underlying material is laid at the bottom of the trench and carefully compacted. It is desirable to lay the material so that part of the sheet slightly extends onto the wall of the basement. This is necessary to create an expansion joint between the blind area and the wall.
• A coating of various materials is laid on top of the inner layer in several layers.

This completes the general device, but for each type of material used to create the outer layer, there is its own mounting technology:

Prepared sand base and exposed formwork on the outside

Seams are placed perpendicular to the walls of the building with a step of 2-2.5 meters. Reiki can be used as guide beacons for the distribution of concrete over the surface of the blind area.

After laying the concrete, the wet surface of the foundation blind area must be additionally sprinkled with cement and smoothed out with a trowel. This process is called ironing and is necessary to increase the moisture resistance of concrete. After the finished structure is covered with a fabric material and periodically moistened with water until the concrete has completely set.

For concrete structures located on unstable and heaving soils, it is recommended to carry out reinforcement. This is done to increase the service life by laying a metal mesh with cells of 10 by 10 centimeters before pouring concrete.

The technology is quite simple and does not require the involvement of specialists. The main thing is to carry out the work in stages and adhere to the basic installation rules.

Construction sealing

Sealed expansion joint

Sometimes, in houses located on heaving soils, a crack may appear between the base and the surface of the structure.

This can be done both at the stage of the device and subsequently in operation. In the first case, the following options are possible:

• The structure must be made on a draining base in the form of sand, gravel and clay;
• The lower part of the blind area should be above the soil around the building;
• The expansion joint must be made in such a way that the tightness between the blind area and the basement wall is maintained.

If these conditions are not met, as mentioned above, a crack may form or the structure may move away from the building. If this happens, then special sealants based on polyurethane are used. The resulting crack is filled with sealant using a mounting gun.

To protect against mold and fungus, the sealed seam is treated with a water repellent.

Construction insulation

Foam insulation and mesh reinforcement

Warming should be carried out when erecting a structure on unstable types of soil. Insulation will help prevent freezing of the soil, thereby preventing soil heaving.

For this, heat-insulating materials are used, which are laid on top of the underlying layer. It is desirable that the outer covering be made of concrete or paving slabs, as this will help to avoid additional stress on the heat-insulating material.

For the usual and simplest thermal insulation, we recommend using extruded polystyrene foam or polystyrene foam.

Structure repair

In case of obvious damage to the outer layer of the blind area, it should be repaired as soon as possible in order to avoid further destruction. To do this, the damage boundary is determined so that the main cracks or potholes are combined into a common plane that can be removed.

It is better to start repair work in cool weather, when the main damage is most exposed under the influence of absorbed moisture.

If the asphalt coating is damaged, it is necessary to remove a layer of material in the desired area to the full depth. The pits, after removing the damage, are recommended to be cleaned of dirt and smeared with bitumen.

Only then can the asphalt concrete be re-laid and compacted. It is desirable that the new asphalt cover the layer of the old pavement. This will give better adhesion to the old material.

Use bituminous mastic and cement-sand mortar. Cracks are cleaned of dirt and filled with mastic. Minor damage can be covered with cement mortar mixed in proportions of 1/1.