Immediately it is worth making a reservation that the foundation of a monolithic slab is not a universal solution to the problem of a heaving layer of soil. But its use can significantly reduce the risk of splitting the foundation base and the building box, thanks to the features of the slab system:
- First of all. the strength and stability of the foundation is almost independent of the thickness of the concrete in the slab structure;
- Secondly. improperly laid and hand-tied reinforcement may not at all perceive bending forces and not equalize the stresses on the slab foundation. It is this type of load that becomes the main cause of the destruction of the base and walls of the building;
- Thirdly. as in most other foundation structures, stability and durability depends on 50% on how effectively you have done drainage and insulation of the blind area with your own hands.
Important! As long as the load on the body of the slab foundation is evenly distributed, even under flooding conditions the slab will stand firmly, like an armadillo. It is necessary to hang any of the parts of the slab base on a point support, even in the presence of reinforcement, the slab will give a crack that is invisible to the eye. Frost and a layer of capillary moisture “cut” the concrete body of the foundation, like a knife.
Therefore, everything that is done by hand on the slab foundation should be aimed at ensuring load balancing. Step-by-step instructions in this matter simply cannot be, therefore many issues, especially when laying a layer of gravel and reinforcement, are solved from practical experience.
Marking and cutting of the foundation stain
Before marking and contouring the contour of the future monolithic basement slab on the pegs, you will need to build your own temporary guideline on the site plan using ordinary sand. In practice, they usually take the silhouette of the base of the base of the slab system enlarged for a meter and a half and draw lines, spraying dry sand from the hands. After removing the surface layer, we mark the exact contour lines of the future foundation.
The surface of the slab foundation must be carefully planned on the horizon. If the size of the slab spot is small, then you can trim and clean up the soil layer with a small tractor, and then clean up with your own hands, using the leveling data. For slab foundations of large volumes it is more rational to use a bulldozer than to dig with your own hands, you cannot do much with a shovel.
At the next stage, without delaying the case in a long box, you need to dig a trench to a depth of at least 60-80 cm with your own hands, bring the pipe to the drainage drain outside the site. Now you can proceed to compaction without the risk of seepage of groundwater. Soil compaction, as well as plot planning, is better to perform with a roller or similar technique; even with a conventional rammer, it is quite difficult to achieve a normal compaction of 10-15 cm. If the ground is excessively wet, we pour a thin layer of fine gravel with our own hands and ram it into the soil layer until the surface of the stain under the slab concrete becomes so dense that traces of high-heeled shoes remain on the layer of dumping.
Laying layers of gravel and sand, step by step instructions
Laying out a layer of geotextile on tamped soil, you can use a road variant or a denser one, under 150-200 g / m 2. We spread the canvases on the surface with overlap at the joints up to 20 cm. To prevent the laid canvas from being sprinkled with sand, we pin the geotextile to staples. To cushion the foundation, you will need to pour a layer of at least 200-250 mm thick. Not to tear the laid fabric, we will lay out in the center of a ditch a path from boards. The sand is used gravel, very large and well washed with water. As you lay in the base of the slab foundation leveling layer and ram it. The final compaction of the layer is performed by a vibromachine after removing the plane of the layer along the horizon.
In a similar way, pour gravel with a layer of at least 10-12 cm. The first layer is in the form of a small 4-20 fraction, then we pour gravel larger, 20-40 mm in size.
Laying waterproofing, installation of formwork and reinforcement for slab base
The waterproofing layer protects the slab foundation from capillary water and at the same time serves as a barrier to hold the concrete mix poured into the formwork. Therefore, we roll a glass-fiber cloth or similar rolled material with an overlap of 10 cm and be sure to glue the seams with a layer of bitumen mastic. If this is not done, a layer of “cement jelly” can lift the edges of the canvases, as a result of which numerous gaps are formed, through which water can easily penetrate to the concrete. For the peripheral areas of the slab foundation, this will mean slow destruction with each frost.
Next, we collect from the harvested shields a simple and affordable formwork design. The corners can be strengthened by stuffing horizontal struts; we carefully release the edges of the waterproofing onto the walls so that they can be fixed to the walls of the slab base.
The reinforcement of the slab foundation is carried out according to the standard scheme, in two layers of the mesh, obtained by bandaging the reinforcement with wire. For reinforcement, we take a bar of 10-12 mm, a mesh window is no more than 20-25 cm. If the ground is very weak, in addition to the reinforcement, we place a layer of four rods separated by 30-35 mm in perimeter, as in the video:
Thus, any precipitation of the edges of the slab foundation until its final hardening will be insured with additional reinforcement. On average, one slab foundation takes at least two tons of reinforcement.
Important! The layer of concrete from the bottom and top surface of the slab to the reinforcement embedded in the foundation body should be no more than 4-5 cm.
How to fill the plate with their own hands
For a thin slab of 200-250 mm, it is better to use high-strength B25-B30 concrete brands. Buying a couple of mixers of the solution, it is better not to risk it, but to acquire material under the slab foundation directly at the plant or office, where it is prepared on the stream. Before pouring install the boards and the draft chute. It is easier to work in two pairs – one adjusts the flow of concrete to the chute, the second pair scatters the pouring mixture in layers into the desired sector of the slab formwork.
If we assume that the purchased concrete will be M200 brands at best, it’s not worth increasing the slab thickness, it is better to use plasticizing agents that stop the mixture separation. In this case, the lack of strength of the concrete slab foundation will be compensated by better adhesion of the material to the reinforcement, there should be no loss of the bearing capacity of the slab base.
It is possible to remove formwork from plate casting not earlier than in two weeks, if there is hot, wet weather, then in 10 days. Even if gaps were formed between the walls of the formwork and the concrete, it is impossible to remove the tree, since the processes of precipitation of soil layers are still under pressure from the slab foundation system. With proper selection of characteristics, the calculated 80% strength of the slab foundation will come in 20-25 days.
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Erecting a slab foundation with your own hands
The slab foundation has the appearance of a monolithic concrete slab, recessed into the ground for a certain distance. These foundations are shallow (plate thickness – 40-60 cm) and deep (thickness can be up to 1.5 m). To build a slab foundation with your own hands, the first option would be more appropriate, since digging a pit, the depth of which is 1 m and more, will require the presence of heavy machinery. Now more about shallow structures.
The slab foundation can be installed even on heaving soils.
The main advantage of the “slab” is that the surface can be loaded with wood, walls of bricks, concrete, etc. In addition, the slab foundation perfectly maintains not only any material, but also a multi-storey building. The “zest” consists in the fact that, with the displacement of the soil, it is not the individual foundation segment that is shifted, but the entire slab. And it greatly minimizes the occurrence of cracks and chips on the walls of the future house.
If a building is built on a different foundation on difficult grounds, it will be more difficult to achieve a similar effect. It turns out that due to this factor, the overpriced price of the slab foundation is already justified. Because if you calculate how much the repair of often cracking walls will cost, saving money on the foundation will not work. Moreover, the slab foundation is a guarantee of truly long-term operation, provided that everything is done correctly. And in order to make a slab foundation and build a house correctly, it is necessary at least approximately to orient in the optimal order of work and to know some important nuances.
- equipment for digging pits;
- wooden slats to level the concrete.
Foundation waterproofing: foundation, grooves.
Now more about this process. First you need to dig a pit, inside which you will make a slab foundation with your own hands. Suppose that this is done and the depth of the space is standard, about 50 cm. As for the width, it is better to make an additional offset along the entire perimeter of the pit. One meter will be enough. This is necessary so that there is freedom of action and there are no restrictions on the area and also for arranging additional insulation for the future construction and installation of the drainage system.
Often the need for drainage is completely forgotten. Therefore, even if the house was made on a slab foundation, but over time it still deforms, you should not be surprised at this situation.
It is necessary to make installation of a drainage system even before the device of the main base.
There is usually a process like this. At the bottom of the pit they dig a number of transverse trenches into which geotextiles are laid. Then plastic pipes with holes for water are laid on top of the material, covered with rubble, then they are covered with geotextiles again – it performs some kind of filter through which water passes, but sand and clay particles do not.
See also: Do-it-yourself construction of a bathhouse
When the drainage system is ready, you can proceed with the installation of formwork. It can be made from ordinary sturdy boards – mega-modern formwork is optional. It is important that the sides of the structure withstand the pressure during pouring and solidification of the concrete mass.
The structure of the slab foundation: sand, gravel, penokompleks, waterproofing, fittings, concrete.
The next stage is a device at the bottom of a sand cushion pit. It is necessary so that the power that comes from the house and the plate is evenly transmitted to the surface along with frost heaving of the soil. So that the sand does not erode during precipitation, it is necessary to put a layer of rubble on top of it. Then additional drainage is obtained.
The physics of the process lies in the fact that the capacity of the moisture head is significantly reduced, while the water passes through a layer of rubble, and the sand pad is subject to small deformation processes and remains intact for many decades.
Sand and rubble just fall asleep enough. It must be distributed as evenly as possible over the surface and then compacted. In this situation, this layer will fully and permanently perform its functions.
On top of the layer obtained, it is necessary to pour a cement-sand screed, the thickness of which should be about 5 cm. This is necessary for the installation of a waterproofing layer, which is made from high-quality roofing material and mastic. When the waterproofing is dry, you will need another layer of cement-sand mortar, approximately the same thickness. This approach allows the waterproofing to be maximally protected from mechanical damage during the further binding of the reinforcement cage.
The structure of the base plate: fittings, concrete, cell size.
It is made of ribbed reinforcement to ensure the highest quality adhesion of steel and concrete. If you ignore this rule, the adverse consequences are not long in coming. For example, during the subsidence of the soil at the base plate a crack may occur, because the expansion of the internal composition of the concrete will not be limited.
And the presence of ribs on the plane of reinforcing rods can effectively reduce the level of stretching of the plate. Therefore, you can not save on the device frame, because of its quality depends on the normal use of the foundation and the entire house.
See also: Staged laying of paving slabs on mortar
Installation is not particularly difficult, and everything can be done by hand. The skeleton is a steel-cage reinforcement cage. Although each object is rather individual, the distance between the reinforcement should be no more than 30 cm. In case the sections are made larger, the strength characteristics of the foundation will be greatly reduced. And this is very fraught with consequences.
Observe the order of construction of the slab foundation.
When the frame is ready, pouring concrete is done. Filling is carried out in a typical way, that is, you can never use cement below M-200. You also need to ensure that, when the concrete mass is poured gradually, and not all at once, the mortar is made only in horizontal layers. It is forbidden to pour individual segments of the area and connect them vertically. In such a situation, all similar compounds, in all likelihood, will simply crack.
This work is over. It is quite realistic to make a slab foundation, since there are no hard moments in the technology.
The most important thing is not to forget to plan communications, because a monolithic slab is not a pile or strip foundation. Then getting to some internal segment will be quite problematic or impossible.
A useful note is that the horizontal deflection of the slab can be significantly reduced by making “stiffeners” on the lower surface of the foundation. These are the usual trapezoidal strips of concrete, protruding from the bottom of the slab and deepening into the ground. It does not cost much, but the final quality will be much higher.
It is still desirable to additionally protect against cracks as a plate, and the house completely. No matter how well the foundation is made, it is impossible to make a power forecast and a scheme for moving the ground 100%. In some situations, the stove can easily bend, so there is a risk of cracks in the walls.
In order to avoid such situations as much as possible, it is necessary to make a reinforced concrete belt around the perimeter of the whole house. which will embrace the walls and will not allow them to disperse. The main thing here is to release the reinforcement out of it and embed the ends deep into the walls themselves. The only point is that this belt does not need to be made of cellular concrete, because they have absolutely not the same strength. The belt is located at the level of the upper contour of the window openings, and, when necessary, it is possible to load overlappings on it.
Such an action in any situation will become relevant, since it will be possible not only to auxiliaryly warm the house, but also to sufficiently reduce the costs for its heating. Make it very easy – you need to fix the sheets of expanded polystyrene at the ends of the plates.
Sources: http://postroj-sam.ru/fundament-doma/plitnyj-fundament-svoimi-rukami-poshagovaya-instruktsiya-sovety-foto.html, http://bouw.ru/article/kak-sdelaty-plitniy- fundament-svoimi-rukami, http://1pobetonu.ru/montazh/plitnyj-fundament-svoimi-rukami.html