Under suburban and multi-storey residential buildings, foundations of various types can be erected. And one of the most popular types of bases are basement. In this case, under the building, there is essentially another floor, which can be used later as a cellar, garage, basement , etc.
What is a
The basement foundation device is more complex than conventional foundations. Accordingly, the technology of construction of such structures differs in some of its features. It is such a foundation, in fact, one of the varieties of slab foundation. In cross section, such a support under the building looks like an inverted letter P. At the base of the foundation of this type, a solid monolithic slab is poured. Further along its perimeter, walls of the required height are erected.
Of course, the construction of such a structure is also more expensive than a conventional slab, strip, and even more so columnar foundation. When pouring the foundations of houses of this type, all the required technologies must in any case be observed exactly. Otherwise, the basement will be inconvenient to operate, and the building itself will not last too long.
What are the norms of SNiP
When erecting basement foundations, the following rules must be followed:
- such a base should go underground rather deeply - below the freezing level, and ideally - by 200-220 cm;
- the floor of the basement should not be located at ground level more than 2 m.
Building foundations with a basement is allowed only in those areas where groundwater is deep enough. Otherwise, the basement in the house will be flooded or it will turn out very damp.
What tools and materials will be required
A foundation of this type is being built in the pit. It’s unlikely that you can dig a hole on your own with an area equal to the area of the house. Excavation under the basement foundation is usually done using special equipment. Therefore, a shovel and a garden wheelbarrow, as when pouring ordinary tape or columnar bases, in this case are not needed.
The foundation for a house with a basement is being built using materials such as:
- rebar 8-10 mm;
- knitting wire;
- waterproofing material.
In addition to the basic materials, for the construction of the basement foundation on the site, you will also need to prepare OSB, boards and burs. They will be needed to equip the formwork. All parts of such foundations are poured with ready-made concrete mixture.
Digging pit
The foundations of the basement are being built with their own hands, like any others, of course, with preliminary marking. Perform this procedure using a building level, pegs, and an inelastic cord. On the site selected for the construction of the house, all garbage is pre-cleaned, bushes are uprooted and the turf layer is removed. Then, in fact, the markup itself is performed according to the method of the Egyptian triangle or two curves.
After the cords are pulled, and the angles between them are checked, they call special equipment. Digging a foundation pit for a basement will cost the owner of the site, most likely, not too expensive. For 2018, such a procedure, for example, costs about 250 r / m 3 .
Preparation of the pit for filling the slab
In the pit dug under the foundation with the basement, first of all you need to carefully level the bottom. Further, a sand-gravel pillow is poured into the pit. This layer will subsequently play the role of drainage and shock absorbing. The thickness of the sand in such a pillow, according to the standards, should be equal to 20-40 cm, gravel - 15-20 cm. Both layers, of course, should be carefully tamped. For crushed stone, you need to use a vibrating plate. It is easiest to compact the sand, laying in layers of 5 cm and carefully spilling water from the hose.
Formwork installation
A monolithic basement basement is being erected, of course, using formwork. The mold for the base plate should be assembled from fairly thick boards (at least 2.5 cm). On the walls of the formwork, when filling the slab, rather serious spacer loads will fall.
The thickness of the base plate is calculated depending on the type of soil on the site, the material of the walls of the house, the dimensions of the latter, etc. But usually when pouring low-rise private buildings, this figure does not exceed 300 mm.
To make the formwork for such a plate, the boards first need to be connected to the boards (two in the same plane). Further, the resulting structures with the help of props deeply driven into the ground should be placed around the perimeter of the pit and fastened together along the length and in the corners. In order to make it easier to remove the formwork from the finished slab, it is desirable to tighten its inner walls with polyethylene.
Base reinforcement
During the operation of the building on the basement floor slab will be a serious load. Therefore, it should be mounted in such a way that it turns out as strong as possible. Of course, the basement slab needs to be poured with reinforcement.
The frame for such a foundation is usually purchased ready-made. But, of course, if you wish, you can connect it yourself. In any case, before installing such a structure at the bottom of the pit, pour a 3-5 cm thick concrete block.
Of course, it is possible to install a carcass on such a substrate only after the cement mortar sets well and hardens. Typically, the reinforcement is mounted in the pit a week after pouring the concrete. In this case, the bottom of the pit is previously closed with two layers of roofing material with an overlap on the walls.
The manufactured frame of the plate after its installation in the pit should be increased along the edges with reinforcing bars. This part will subsequently strengthen the walls of the basement.
Plate Fill
For this procedure, as already mentioned, in the vast majority of cases, owners of suburban areas hire special equipment. Ready concrete mortar will cost, of course, more expensive than self-made. But the work in this case will be done as soon as possible. The plate when using special equipment will be flooded at once, without interruption. And consequently, it will turn out as reliable, strong and durable as possible.
Wall Fill
It is also unlikely that it will be possible to manually erect this part of the foundation construction with a basement floor. The height of the wall of the base of this type is usually significant. Pouring them, of course, is also worth simultaneously with the supply of a solution from the tank.
This part of the base is being erected using the same technology as the strip foundation. On the basement, it will subsequently act as walls. To erect a tape of such a foundation, the formwork is pre-mounted. Install it in such a way that the reinforcement cage removed from the slab subsequently appears in the thickness of concrete. The distance from the outermost rods to the walls of the formwork should be approximately 5 cm.
It is easiest to mount a form for a basement tape from a bar and OSB. In this case, a lattice frame is first constructed from lumber. Further, it is simply sheathed from the inside with OSB sheets.
Recommendations of pouring specialists
To lay the concrete mixture during the construction of the basement foundation, of course, you need to correctly. During the supply of the solution, it should be leveled and pierced with a shovel from time to time. This will remove air bubbles from the concrete mix and make it more uniform. As a result, the foundation slab and its walls will be as strong and durable as possible.
After the formwork has been removed from the flooded base, the structure should be covered with polyethylene. Subsequently, the foundation should be watered from time to time for two weeks. This will avoid the formation of surface cracks on it.
Foundations of basement floors from FBS
Most often, the bases of this type are poured under the houses on the spot according to the technology described above. But sometimes such foundations are also built using ready-made FBS blocks. In this case, installation of the base of the house is more expensive. But at the same time, block foundations are erected much faster than floodplain ones. In addition, the owners of a suburban area when using this technology do not have to wait for the maturation of the concrete base in order to start erecting a box of the building.
FBS blocks are stacked when assembling the basement in a checkerboard pattern. That is, with a shift, so that the seams between them do not converge at one point.
Floor assembly
So, we figured out how to fill the foundation of the basement or assemble it from blocks. At the final stage of the construction of such a base, a ceiling is installed, which is a basement ceiling.
A variety of technologies can be used to assemble such structures. Most often, the overlap on such a base is laid, of course, reinforced concrete. But if you wish, on the ground floor you can also assemble a regular ceiling on beams with a planking.
Hydro and thermal insulation
To make the basement subsequently dry and warm, these two procedures should be performed without fail. This operation is usually started immediately after the assembly of the floor. Thermal insulation and waterproofing of the basement is carried out as follows:
- on walls staggered using plastic dowels, glued polystyrene boards with a density of 45-50 kg / m 3 ;
- They cover the foundation with roofing material or they coat the insulation with two layers of bitumen mastic.
Waterproofing the basement of the basement should be as high quality as possible. Failure to comply with the technology for performing this procedure will lead to a significant reduction in the service life of the entire building. At the final stage, backfill the foundation with coarse river sand.
Basement ventilation
So that in the future, in the basement of the house, it would not be too damp, when erecting such a foundation, among other things, it is supposed to make vents. That is, leave holes in the walls. 2-3 meters of foundation tape should have one such outlet (of course, above ground level). The ventilation area of natural ventilation, according to the regulations, should be equal to about 25 cm.
For large country houses on the basement floors, forced ventilation can also be arranged. In this case, the foundation will most likely have to provide only one intake hole. Subsequently, the sleeve of the supply air duct will be withdrawn into it through the pipe.
At the final stage of arranging ventilation in the basement, among other things, it is recommended to install an alcohol thermometer and a psychrometer designed to determine relative humidity. According to the regulations, the air temperature on the basement floors should be kept at 16-21 ° year-round. The humidity in the basement should be equal to 50-60%.
The final stage
After the basement foundation of the country house will be erected and laid out, it is necessary to equip a fairly wide blind area around it (preferably 1 m). To do this:
- remove soil from the foundation to a width of 1 m and a depth of 30 cm;
- install the formwork in the resulting pit;
- pour a small amount of clay (5 cm) at the bottom of the pit;
- on top of clay lay a layer of sand of 5 cm with tamping;
- pour crushed stone with a layer of 10 cm;
- put reinforcement mesh on the rubble.
At the final stage, the formwork is poured with concrete with a slight slope away from the foundation. The blind area is equipped, as you might have noticed, quite easily. At the same time, it will be very effective in protecting the foundation from rain and melt water.