How to make a concrete blind area around the house with your own hands

Recommendation points

• The best time to get started
• Functions and basic parameters of the concrete blind area
• Paving options for every taste
• Reinforcement, formwork and expansion joints
• We carry out concrete work
• Post-processing and maintenance of the blind area

This key point of foundation protection is relegated to the background in many home projects. Nevertheless, the blind area around the house is an integral part of any durable and strong building. When and how to properly make a blind area around the house – these are the main questions of today’s educational program.

The best time to get started

It is often believed that the blind area around the house is cast after finishing work is completed. However, there are a number of reasons to do this as early as possible. The first of them – the foundation needs to be protected from leakage from the very first day, and especially after the construction of the roof.

It is also obvious that the paths around the house are most useful for finishing work. There will be no dirt under your feet, there is the possibility of a stable installation of scaffolding.

We propose to cast the blind area literally immediately after the foundation has set. So you will not stretch the concrete work, or even be able to cast the tracks on the same day with the foundation..

Functions and basic parameters of the concrete blind area

When moistened, almost all types of soil lose their hardness and become plastic. Imagine what happens when the soil under the house is unevenly moistened: in some places the foundation will sag and bend, cracks appear on the walls.

This phenomenon is most typical for houses with a two- and a pitched roof without a drainage system, but it can manifest itself in buildings of completely different types in areas with heavy rainfall.

If we imagine a cut of the soil, then the water on it will spread in a cone, the width of which depends on the hygroscopicity – the permeability of the soil to water. This value varies depending on the type of soil, as well as on the depth of its occurrence. On average, water per meter of depth has time to seep to the sides by 50–80 cm, and at a depth of two meters, moisture flows down 100–140 cm from the point of contact with the soil.

Of course, there is no need to remove absolutely all rain or melt water, but it is necessary to prevent its accumulation in loam pockets. Therefore, choose the width of the blind area about 60 cm per meter of foundation depth, but not less than 45 cm. The optimal slab thickness is 90–120 mm, depending on the final width.

1 – the foundation of the house; 2 – sand filling 150-200 mm; 3 – crushed stone; 4 – concrete min. 150 mm; 5 – waterproofing; 6 – drain; 7 – reinforcement of the blind area; 8 – paving slabs; 9 – drainpipe

Paving options for every taste

In the general case, it would be the right decision to bring the blind area to the level of coverage of the local area. Let’s call this level the zero point..

The blind area can be arranged hidden, so the house is closed in a ring of paving slabs. In this case, the slab is lowered below the zero point by a tile thickness plus 15 mm. It will be convenient to fill the blind area using curb stones as formwork. Such a device allows you to accurately bring the tile close to the plinth without breaking the coating.

The tiles can be laid on top of the grout or simply on a clean-screened cushion by moving the board another 50 mm lower. In the latter case, there will be no displacement of the tiles, but 16 mm holes must be made in the curb stones for water drainage.

The use of “bare” concrete is also perfectly acceptable. The slab is set at zero level, it is possible to frame it with curb stones. For long-term operation without peeling and resistance to falling water flows, the surface must be additionally strengthened. If the blind area is under the gutter, the original technique would be to use stencil frames for garden paths.

Reinforcement, formwork and expansion joints

Calculate the depth of soil removal from the zero point, taking into account the thickness of the slab and 15 cm of the backfill layer. When the wide trench has been dug, reinforce the outer edge with a 10mm edged board, the top end of which is set in the top plane of the slab as a leveling beacon. For the correct installation of the curb stones on the sand, bend the upper edge of the formwork outward by 10-15 mm from the vertical. Roll out a strip of roofing material 30 cm wide along the base.

Fill the bottom of the trench with 15 cm with a layer of 50–70 mm crushed stone, then at intervals of no more than 2 meters, install 10×100 mm wooden slats across the blind area. Their upper edge is brought out flush with the surface of the concrete slab, the edges from the house must be raised 15–20 mm from the horizontal. The task of the slats is to compensate for the thermal expansion of concrete outdoors. With a wide rule or rail you can also use the planks as alignment beacons.

Two reinforcement lines are arranged in the formed cells. The lower mesh of 10 mm reinforcement with a cell of not more than 150 mm is installed on spacer plugs that provide a lower protective layer of concrete of 40 mm. The reinforcement of the upper part has the task of strengthening the outer concrete layer. A mesh of wire 3 mm with a mesh of 75 mm is tied to the bottom on U-shaped brackets.

We carry out concrete work

We prepare concrete with a fine aggregate, granite chips and screenings are perfect, in any case, the fraction should not exceed 30 mm. The mixture contains one part of 500 grade Portland cement, four and a half parts of filler and one part of quarry sand. Stir until the stones are completely enveloped in cement milk, in order to speed up the process, add a few drops of dishwashing detergent to the water.

Pour the mixture under the edge of the blind area, then slide it towards the building, achieving high-quality spilling and filling without voids. At the end, adding concrete in small portions, pull it along the guides and smooth it with a float.

You need to level it carefully, removing an unnecessarily thick layer of floating milk and adding hard concrete to this place. After pouring one area between the compensation slats, go to the next and so on around the house.

Post-processing and maintenance of the blind area

To give high strength and wear resistance to the concrete surface, it is necessary to catch the moment when the concrete mass has already grabbed, but the concrete surface is still wet. At this stage, the blind area is subjected to ironing with a cement-sand composition.

The mixture is prepared from 500 Portland cement and washed quarry sand in equal proportions. The ingredients must be dry at the time of mixing. Using a sieve, we scatter the mixture over the concrete blind area, achieving a layer of sprinkling of at least 3-4 mm. Now you need to wait until the entire layer is saturated with moisture and darkens. If the process is delayed, moisten the surface with a hand spray. Use a mixture of water and liquid glass in equal proportions if you want to add extra strength.

After the crust is moistened, take a flat trowel and rub in the top coat with light pressure, level carefully and achieve a uniform finish. As a result, the surface should be dark gray with blue color, after drying, glossiness appears.

As the concrete dries, it must be constantly moistened to avoid cracking. The hydration of cement takes place almost completely in 14 days, for this period it is also recommended to cover the blind area with film and slate.

At least once a year, the blind area should be checked for peeling and cracking, especially in the absence of drains. Small cracks are sealed with a strong cement solution, in case of peeling of the iron crust, it is repeated, but already with wet compounds. Once every 3-4 years, reinforced concrete should be impregnated with sealers, as well as in the case of signs of looseness of the mass or flaking.