How to make a cellar in a house or garage with your own hands

Recommendation points

• What to do first: foundation or basement walls
• What to do if the building has already been built
• Do I need to insulate the basement
• Does the basement need a foundation
• What material to build walls
• What to do with the overlap if the yard and traffic load are above the basement
• Is it necessary to bury the basement completely
• Groundwater rises above the floor, what to do
• The basement is damp and cold, does it need to be heated
• Entrance from a narrow room and a steep staircase – can you fix it?

The arrangement of a cellar with an entrance from an aboveground room can be fraught with a number of difficulties. Your attention is invited to an analysis of ten main questions about work planning, basement construction technology, as well as about the materials and technical means used.

What to do first: foundation or basement walls

The order in which concrete structures are erected depends on their spatial location. In the ordinary case, the neck and the main basement room lie entirely under the shallow strip foundation (MZLF) and do not come into contact with it in any way. Pouring is carried out in the direction from the lower structure upwards, periodically collecting the formwork or pouring the separating layers of soil.

In some cases, the concrete basement frame can be cast together with NZLF. If the entrance corridor in space intersects with the foundation tape or basement wall, their monolithic device will have a positive effect on both the strength and waterproofing of both structures..

The foundation can also be poured before starting work on the basement. This is usually done from the consideration that at a high level of groundwater (GWL), it is easier to remove the soil in the drained area, and the foundation itself serves as a ready-made spatial reference point and an object of reference. This order of installation is most beneficial when the basement is located entirely within the inner limits of the foundation..

What to do if the building has already been built

It is quite difficult to add a basement to an already built house, especially if the entrance is planned from the interior. The best way is to make a doorway in the outer wall and place the basement completely outside the floor plan. For entry, an inclined neck with a staircase is used, the arch of which is partially located above the ground.

Basement, equipped outside the main plan of the building with an inclined neck and an entrance from the inside of the living quarters: 1 – sand preparation; 2 – concrete base; 3 – monolithic concrete walls; 4 – insulation for a shallow cellar; 5 – ventilation; 6 – inclined neck; 7 – doorway

The benefit of this method is that construction work inside the building is minimized. The basement is excavated entirely from the outside, only the upper platform of the stairs and the edges of its oblique supports are connected to the concrete foundation.

It is important that the walls of the staircase corridor have a monolithic connection with the steps and rise above the ground at least 50 mm, serving as the basis for masonry. The above-ground part of the passage is laid out with ordinary brick, it is also possible for them to create a vault.

The main problem is that this way of entering is a strong gap in the thermal protection of the house. It is necessary to exclude the intake of warm air from the house by installing along the door in the lower and upper part of the neck in the manner of an airlock. It is also recommended to additionally insulate the place where the neck joins the wall of the house, at least the next 50-80 cm in all directions to prevent the formation of ice at the door block.

Do I need to insulate the basement

The most difficult task in building a basement is to ensure a suitable climate inside and a separation of the air temperature from the colder below to the warmer one under the floor. To prevent the formation of condensation on a cold ceiling, the basement is usually located completely below the freezing depth.

The basement can be insulated with any materials with minimal water absorption that are not afraid of direct contact with the ground: polyurethane foam, foam, extruded foam, and the like.

If the temperature of the soil layers adjacent to the walls and ceiling does not fall below 3-5 ° C, the conditions for placing the basement can be considered satisfactory. In other cases, before backfilling the soil, the basement can be fenced with a layer of foam insulation.

Does the basement need a foundation

The walls and roof of the basement take on the load from the overlying soil layers and are subject to lateral pressure from the soil. Therefore, a solid monolithic base for the basement is necessary.

The basement foundation usually rests on a sufficiently dense soil layer, so additional deepening is not required. A 25×35 cm tape with four rows of 14 mm reinforcement will be enough, distributing the load in two main sections. The foundation should be cast over a preparation layer of 150 mm with concrete of 100 or 25 cm grade, filling from crushed stone with a fraction of 50–70 mm.

The design described is suitable for a location above the actual water table. If the basement requires solid waterproofing, the floor slab and walls are cast in one piece.

What material to build walls

If it is possible for equipment to approach the construction site of the basement, it is better to make the walls reinforced concrete on the panel formwork. It is recommended to use prefabricated concrete mix to ensure the highest quality waterproofing. Firstly, the walls will be cast without “cold” seams, and secondly, it is possible to use concrete with a guaranteed water absorption rate of W8 or lower.

If the basement is not subject to flooding, the only limitation for the wall material is the strength grade – not lower than M250. Solid clay or sand-lime bricks, gas and foam concrete of low porosity are suitable. The main advantage of concrete work here is a relatively high speed, so walls can also be poured from a concrete mixer.

In fairness, we note that even non-monolithic walls can be equipped with reliable insulation. But the funds and materials for its device will cost more..

What to do with the overlap if the yard and traffic load are above the basement

The overlapping device in the basement is the most critical stage, even if there is no additional load on the ground. Reinforcement with mesh is optimal for a span of up to 4.5 m, for a greater length, a system of load-bearing beams is needed.

The most useful slab construction for additional load is a concrete slab cast on a permanent formwork from profiled sheet. In addition to the numerous stiffening ribs, the ceiling will receive a finished interior decoration of the ceiling.

The approximate thickness of the slab, taking into account the stiffeners, is about 250 mm. Reinforcement takes place in two rows: pin reinforcement on spacer plugs is laid in the edges of the profiled sheet, and the main plane is reinforced with a 14x200x200 mm mesh with an upper protective layer of about 60 mm. Such an overlap can be used to cover a span of 6–8 m without the use of steel beams with the possibility of collision with a car.

Is it necessary to bury the basement completely

The basement can only be partially buried in the ground if the geomorphological conditions do not allow providing the required burial depth. In this case, the upper part of the basement will need insulation. As a rule, it is performed with foam or EPS plates, which, after temporary fixation, are covered with a mound of soil.

This is how an unburied cellar can look like with a fill and an earth embankment on top of it.

The use of geotextiles at the boundary of the layers will make it possible to create a stable, stable embankment with the use of bulk insulation material – expanded clay or broken foam glass.

Groundwater rises above the floor, what to do

Before building a basement, a well is usually made with a garden drill, measuring the level of the groundwater table throughout the year. If the water is closer than 20 cm to the floor level, the need for a deaf encircling waterproofing is obvious.

But do not rush to blindly isolate the basement from the water, without determining the path of its entry. Flooding can be caused by rainwater seeping through the soil layer and overlap. When pouring the floor, the slope and roll out of a one-piece barrier made of thick polyethylene film should be provided.

If moisture slowly seeps through the wall, it is enough to surround the basement with a clay castle. If groundwater penetrates under strong pressure through walls and floors, which translates into a very rapid flow of water, a continuous waterproofing will have to be performed. And it is much easier to arrange it immediately at the construction stage, especially for the floor slab..

The basement is damp and cold, does it need to be heated

Violations of the climatic regime are mainly due to improperly organized ventilation. Too active air exchange in winter will cool the basement, and in summer it will cause huge amounts of moisture along with hot outside air..

Active ventilation in the cellar should be used carefully, knowing in advance how humid or dry, cold or warm air coming from the street will behave

Basement heating is usually not performed. But if you place even a small heat source (a 100 W light bulb) right under the chimney, it will speed up the air exchange and the “fogged up” cellar will dry out much faster.

Entrance from a narrow room and a steep staircase – can you fix it?

For a basement or cellar, the organization of space and the convenience of the entrance neck are far from the last thing. Folding ladders and steep stairs are less and less suitable. Preference is given to more practical stairs with a low riser. But sometimes a vertical entrance to the basement cannot be avoided, so you should think about optimizing it..

Spiral ladders of various shapes and designs can fit into the neck of almost any shape and size

If possible, it is advisable to expand the drain neck to 100–120 cm, which will be enough for the construction of the simplest spiral staircase made of metal. The size of the room may not allow this, but there is little to prevent you from making one of the walls of the neck sloping. We are talking about the wall opposite the stairs, ideally it should have the same slope. Do not forget that with a set of depth you can go to more gentle concrete steps, there is almost always room for a small area. Do not be too lazy to fix several handrails or brackets on an inclined wall – this way you don’t have to go down forward with your back.