Building a cellar indoors

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The construction of a cellar or a small basement room remains relevant to this day. Constructions of this kind are very popular among summer residents and owners of private houses. In most cases, the construction of the cellar is carried out separately from the living quarters, but there are situations when the owner needs to build a small basement under the shed or, say, under the house. Today we will talk about how to do it competently and efficiently..

Building a cellar indoors

We carry out the markup

First of all, we need to decide on the location of the basement. It is desirable that it is not located directly in the center of the room, but closer to one of its walls or corners, this step is designed for further installation of the ventilation outlet, since the pipe will be taken outside the building to the street.

We will take the walls of our premises as a standard for marking. We measure from the corner one meter on the lower part to either side of the wall, then directly perpendicularly transfer this mark to the floor, so we get the first point that will be one meter away from both walls of the corner. Suppose we need to build a basement with a size of 2×3 m and a depth of 2.5. We will take the second point along the wall that is longer, it will be 4.4 m away from the corner, and the perpendicular projected onto the floor will again be one meter, connecting these two points on the floor, we get the first segment, which will be the mark for the first 3.4 m long wall. The additional 0.4 m dimension is for wall thicknesses on both sides. In a similar way, we draw an adjacent segment of 2.4 m. With the help of long laths and a square from the free points of the corner formed on the floor, we draw the other two sides, which should close our rectangle. Be sure to measure the diagonals, they must match each other with a maximum tolerance of one centimeter.

Marking the concrete floor for the cellar

Removing the concrete floor

If you have a thin screed on the floor, then the procedures for removing it will be very easy. The main tool in this business is a grinder with a diamond wheel for concrete. It will perfectly cut the contours of the rectangle, thanks to which we will physically separate the unnecessary part of the floor. Then take a jackhammer and dismantle the entire internal area..

Dismantling the concrete floor under the cellar

If your floor consists of a relatively thick layer of concrete, plus it is also reinforced, then you have to work harder – just draw a contour with a grinder, not going deeply, then dismantle everything with a bump stop. When you come across the reinforcement rods, carefully clean them from the concrete and cut them off with a grinder using a metal disc. When cutting the rods, leave thirty centimeters from the edges, let them stick out, in the future, with their help, we will “tie” the new floor to the floor plane.

Dismantling a concrete screed with a jackhammer

Important! Before doing work with a grinder, carefully hang up the nearest windows with rags or cellophane, sparks and concrete flying off the disk can damage them.

Roy pit

It is necessary to dig a hole along the contours of the removed concrete, it is clear that ideally flat walls will not work, but if possible, follow these procedures carefully, since any crumbling side in the future will become an unnecessary consumption of concrete when erecting walls.

According to our conditions, the working height of the cellar should be 2.5 m, which means that it is necessary to dig a hole 2.8 m deep, taking into account the bottom screed (10 cm with backfill) and a ceiling thickness of 20 cm.

Digging a hole for the cellar

Lower plinth

In order to make a support under the walls, we need to cast a basement, which in its structure resembles a strip foundation, but in our conditions it will be much simplified.


In the inner room of the cellar, the basement should protrude about 0.2 m from the intended walls. This means that its width should be 0.4 m (taking into account the thickness of the walls).

The marking of the basement is carried out in the same way as the marking of the floor for dismantling, only here we still need a plumb line in order to correctly transfer the size down vertically. From the corner to the long wall we measure a segment 1.4 meters long and make a mark on the wall, then set the perpendicular to the side of the cellar, for this we put a rail at the end of which a plumb line is fixed, we achieve a complete state of balance from it and at the mark below we insert a rod of reinforcement, which will be located in the place of the first inner corner of the base. In our case, the parameters of the cellar are 2×3 m, the base protrudes inward by 0.2 m, which means that the internal parameters of the base are 1.6×2.6 m. The marking of the remaining points must be carried out based on these data. At the final stage of marking, the diagonals should be checked again, they should coincide with the minimum tolerance.

Basement marking for the cellar

Formwork and filling

Around the perimeter of the basement, it is necessary to dig a small trench with a depth of 0.3 m.It is not at all required to make the formwork on both sides and in full depth, it is enough just to put it in the inner contour so that the concrete keeps its shape, and in the places where the basement joins the soil, it completely optional.

To install the formwork, we need four boards 0.1 m wide, two of them will be 1.6 m long, and the other two – 2.6 m. Before installing the formwork, it is necessary to level the ground. Next, we knock down a rectangular box from these boards, in the corners you can fill small square bars to make the formwork stronger. We install it according to the markings and check the level, if it does not partially match, then you can dig or add earth at the place. From the inside of the cellar, before the formwork, we drive the reinforcing rods into the ground, at a distance of 50 mm from the formwork, insert wooden blocks between the rods and the tree, they will play the role of a spacer to firmly fix our structure.

Foundation formwork for the cellar

Along the perimeter of the base, we will make a filling with slag. The thickness of the slag layer should be about 10 cm, carefully spill it with water and tamp it.

Reinforcement and pouring

Reinforcement of our base can be done in the simplest way, in one plane. To do this, we need 6 long rods of 2.5 m each and 6 short ones – 1.5 m, these will be longitudinal rods, for transverse reinforcement we will cut 30 cm rods, which we will lay in 0.1 m increments, we will need about 90 pieces.

First of all, pour concrete to half the level, then put the longitudinal and transverse bars of the reinforcement, then pour everything to the final level.

Among other things, we will need another 90 half-meter pieces of reinforcement. After the basement is poured, they will need to be inserted into fresh concrete in a strictly vertical position, at a distance of 0.3 m from the inner level of the basement and with a step of 0.1 m.In the future, we will tie the wall reinforcement to these rods.

Ready foundation for the cellar


We will make the walls for our cellar of concrete. For their construction, as in any reinforced concrete structure, you will need a reinforced frame and formwork.

Wall reinforcement

You can knit a reinforced mesh for the walls the next day after pouring the basement. For the installation of the mesh, we need 90 pieces of reinforcement 2.5 m each, 50 pieces of 1.6 m and 50 pieces of 2.6 m. The grid spacing will be 0.1 m.

All four planes of the walls should be set strictly vertically, at the corners there should be a strong bond, so that the frame does not walk or stagger.

Building a cellar indoors

In advance, it is necessary to leave two holes 0.2×0.2 for future ventilation. The first hole should be located at a height of 0.5 m from the floor and 0.3 m from the wall, this will be the bottom ventilation hole of the cellar. The top vent should be located 0.5m down from the ceiling and 0.3m from the wall. Both openings should be diagonally distant from each other and adjacent to the outer walls of the house, so that the ventilation pipes can subsequently be brought out into the street.

Formwork installation and casting

The walls will be filled in two stages, for the first time we will fill one and a half meters in height, for the second – the remaining one meter.

The formwork will consist of four solid shields, two shields 3×1.5 m and two shields 2×1.5 m.Similar shields can be assembled from ordinary boards by cutting them in length and knocking them down with nails on the crossbars, the distance between which is about one meter.

Installation of formwork for walls

The most difficult thing is to set the entire structure straight, for this you need to use long spacers, they are placed inside so that the shields do not fall through, you also need to use small bars that are laid between the formwork and the wall. All these procedures will help us to set the formwork quite evenly..

As in the case of the plinth formwork, in the places where the corners meet, it is necessary to fill the timber, thanks to this we will give rigidity to our structure.

After the formwork is exposed, you can start pouring. The main thing to remember is that this process cannot be automated, do not use a concrete hose or something like that for pouring, it is best to fill from a bucket, time and effort, of course, spend more, but the end result is worth it.

Pouring the walls with concrete

After pouring, it is required to tap the formwork a little with a rubber hammer, this will help remove air bubbles, in addition, this procedure contributes to a more even distribution of concrete.

It is recommended to remove the formwork no earlier than in a week, during which time the concrete will have time to fully grasp, since for pouring the second section of the wall we need a solid support in the form of the first section.

The installation of the formwork for the upper row is done in such a way that the upper level of the boards is 0.21 m below the floor level, for this we will take the necessary measurements and draw a horizontal contour on the finished wall of the cellar. This outline will show the level of overlap between the bottom wall and the upper section formwork. If all calculations and measurements were performed correctly, then this level will be 0.49 m.

To fix the lower edge of the formwork, it is necessary to drill through holes for the reinforcement in increments of 0.5 m along the horizontal contour, which is drawn on the wall.After that, we hammer the reinforcement so that it sticks out of the wall by 0.1 m. In the future, we use these rods we will put the formwork. In order to ensure the vertical level of the structure, it is necessary to put spacers between the panels from the inside, again we use small bars for laying between the shield and the wall.

This procedure is relatively difficult, so you will need two more people to help. Pour the walls carefully, as in the previous case, after pouring, tap the walls with a rubber hammer.


Immediately after pouring, it is necessary to make a base for the floor, it will be presented in the form of metal plates. The size of one plate is 200×200 mm and a thickness of 5–10 mm. On the one hand, it is necessary to vertically weld two rods of reinforcement 0.3 m long, with the help of these improvised legs, the foundation plate is embedded in fresh concrete. In general, we need 12 similar plates, they are located on the long walls of the cellar, two are extreme in the corners, and the rest are between them at a distance of about 0.5 m from each other. Strictly observe the horizontal level between all the plates, both along and across, because this will become a reference base for the cellar ceiling.

Embedded for floor beams


While the walls are at the drying stage, so as not to waste time, we will proceed with the installation of ventilation outlets. For them, we previously left two holes in the reinforced frame, now you need to hollow out the concrete opposite them. On the back side of the walls of the house, opposite which the future ventilation holes are located, we need to dig two holes, one with a depth of about 3 m, the second – 1 m.After that, from the inside of the cellar we gouge holes in the ground outward, so that they dock with the external vertical holes in the soil. To simplify the procedure, use a probe instead of a shovel, thanks to it you will only dig out the ground that interferes with the laying of pipes. Next, lay the ventilation pipes and fill everything back with earth, spill the earth with water and tamp it, this will ensure a solid fixation of the ventilation outlets.

Ventilation device in the cellar


Like the entire cellar, the floor will also be reinforced concrete, in fact, we will restore the floor that was removed at the initial stage, only it will now be reinforced with I-beams.

We need 6 I-beams of the 20A brand, 2200 mm long, the weight of one such segment is about 46 kg. The beams are placed next to the embeds with the same pitch, the last time we check the accuracy of all levels and weld the beams to the embeds. The resulting crossbars will be a solid and reliable base for the cellar ceiling.

Installation of the beams of the cellar ceiling

For the construction of the formwork, it is necessary to use OSB sheets with a thickness of 20 mm. We do not touch one extreme span between the beams, in the future an entrance to the cellar will be built there.

Formwork boards must be placed underneath the I-beams (after having covered the surface that will come into contact with concrete, oilcloth), they must fit snugly to the beams, use vertical struts to fix them, the more racks, the stronger the structure.

When we dismantled the floor at the very beginning of construction, we were left with 30-centimeter pieces of reinforcement sticking out horizontally, now we will simply restore this mesh. We lay 2-meter rods between the finished sections and tightly tie them together at the joints. After that, according to the procedure already known to us, we lay and tie the transverse rods in increments of 0.1–0.15 m so that a full-fledged mesh is formed. That’s it, now you can start filling.

Reinforcement of the cellar ceiling

As with the walls – no automation, everything is manual. We fill the spans evenly over the entire surface of the floors, so as not to overload individual parts of the formwork. Between the upper level of the I-beam and the floor of the house, we have a height margin of 10 mm, this is done so that you can fill them with concrete from above, hiding all the iron in the floor.

Installation of beams and pouring of the ceiling must be carried out after the walls are completely dry, depending on weather conditions, this may take from 2 to 3 weeks.

While the ceiling is completely standing and dry, a month will pass, but the dismantling of the formwork can be done in two weeks.

Home cellar hatch

All of the above procedures will take two or three people about a month of work (excluding the drying out of the floor), after which you can proceed with the installation of electrical wiring and the construction of a concrete screed on the cellar floor.

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