Subtleties of calculation of the base plate

Modern houses are built on different foundations. The choice directly depends on the loads, the relief of the selected terrain, the structure and composition of the ground itself and, of course, climatic conditions. This article reveals the full information about the slab foundation, lucidly answers the question of how to properly make a complete calculation, which will help build the desired foundation.

The tiled type of the foundation consists of a building base, which is a flat reinforced concrete slab or with stiffeners. The design of this foundation is of several types: team or monolithic.

The prefabricated slabs made at the factory are called the precast foundation. The plates are laid by the construction equipment on a previously prepared, that is, leveled and compacted foundation. Here airfield plates (PAG) or road plates (PDN, PD) can be used. This technology has a big disadvantage. It is connected with the lack of integrity, and, as a result, with the corresponding impossibility of resistance to even the smallest movements of the ground. It is for this reason that the prefabricated type of slab foundation is mainly used only on rocky surfaces or on non-dull, coarse-grained soils for the construction of small wooden structures in areas where there is a minimum freezing depth.

But the monolithic slab foundation is one whole rigid reinforced concrete structure that is being erected below the area of ​​the building itself.

Geometrically, this type of foundation is of several types.

• Plain. When the underside of the foundation tile is flat and even.
• Reinforced. When the underside has stiffeners, which are arranged in the order calculated by special calculations.
• USP So called the warmed type of the Swedish plates which belong to a kind of base plates of the strengthened look.During construction, a unique technology is used: the concrete mix is ​​poured into a separately developed factory type of permanent formwork, which allows you to further form a reinforced and small stiffeners on the elastic base, or rather, in its lower part and on the surface. USP also has a heating system.

This article talks about the simplest monolithic slab foundation.

The first advantage is almost perfect universality. Sometimes in the network you can meet articles that say that you can build a foundation tile everywhere.

It turns out a kind of "concrete ship", which has a top add-on from the whole house.

And yet the following remark will be fair: the only foundation that allows for a fairly reliable construction on planting and heavily lumpy soils, including marshy soil type, is a pile foundation.This type of foundation is used when the piles have enough of their own length to fix in the lowermost bearing soil layers.

The frosty type of swelling, including subsidence, during the thawing or subsidence of the foundation due to the wetting of the ground surface (for example, during the rise of groundwater) cannot equally occur under the surface of the entire tile. In any case, only one of the parties will shift more. A simple example is the spring thawing of a dirt surface. The thawing process will proceed much faster and with greater intensity on the south side of the house than on the north. Meanwhile, the tile will be subjected to enormous loads, which, by the way, it does not always withstand. All this will affect the structure: the house can simply tilt. It will not be so scary if it is a wooden structure. And if it was built of brick or blocks, cracks may appear on the walls.

The slab foundation makes it possible to build houses even on the most difficult soils, to which the medium-soil type, which has the lowest bearing capacity, is, rather than, for example, tape soil.That's just not to overestimate this opportunity.

Do slab foundation use during the construction of large buildings? Some argue that on a monolithic slab, you can only build the lightest and at the same time not enough durable buildings. This statement is not entirely true, because when choosing favorable conditions and a correctly designed foundation with competent construction work, the slab foundation can even withstand the Central Department Store. By the way, the building was built on a slab.

Too high price. This opinion is for some reason common. Almost everyone is sure that the slab type of foundation is very expensive, more expensive than the existing types of foundation. Also, for some reason, the majority believes that the cost will be about half of the available costs for all subsequent construction work.

At the same time, no one has ever conducted any comparative analysis. Also, for some reason, many do not take into account that during the construction of a house, for example, flooring will not be necessary. Of course, it says about the rough floor surface.

The complexity of the work itself.The following statement is often heard: "For the construction of a slab type foundation, the experience of skilled workers will be needed." And yet, if you estimate, it becomes clear that such "masters" greatly overestimate the prices for their work. In fact, only ignorance of technology usually leads to errors, and bloat can be with any other foundation.

So what kind of difficulties can be encountered while working with a slab foundation? When leveling the site? No, everything here is also no more complicated than when leveling a recessed strip foundation. Maybe the difficulty with waterproofing or insulation? Here, rather, it is better to perform these operations on a flat horizontal surface than on vertical planes.

Maybe it's in the mating reinforcing cage? Again, it is necessary to compare and understand that it is simpler, for example, you can take the reinforcement laid out on the platform even, or you can reach into the ribbon foundation itself with its formwork. Maybe it's in pouring the concrete mix itself? In this embodiment, it does not depend on the selected foundation, but rather on the characteristics of a separate section, on whetherWhether the mixer will be able to drive up to the construction site or have to mix concrete manually.

In fact, to build base plates - physically difficult task. Because of the rather large construction area, this work can be called tedious, but it does not say here that the help of qualified builders will be required. Therefore, the usual “wrist” men will be able to cope with this. In addition, if you correctly follow the construction technology and the SNiP of the columnar, slab and other foundations, you will certainly succeed.

Each zero cycle will require a calculation, which consists primarily in determining the thickness of the plate itself. This choice cannot be made approximately, since such an unprofessional solution of the question will lead to a weak base that can crack in the cold. Too massive foundation of a deep foundation is not done, so as not to waste unnecessarily extra money.

For self-build houses, you can use the calculation below. And let these calculations not be compared with engineering, which is carried out in the design organizations,Yet it is these calculations that will help in the implementation of a high-quality foundation.

It is necessary to study the soil located on the selected building plot.

For further calculations, you will need to select a certain thickness for the base plate with an appropriate weight. This will help to get the best specific pressure on the existing type of soil. When the loads are exceeded, the structure usually begins to “sink”, with minimal loads, a slight frosty swelling of the soil surface will lay down the foundation. All this will cause not very pleasant consequences.

Optimum specific pressure for a soil surface on which construction is usually started:

• fine sand or dusty type of high density sand - 0.35 kg / cm³;
• fine sand with an average density of 0.25 kg / cm³;
• sandy loam in solid and plastic form - 0.5 kg / cm³;
• plastic and solid loams - 0.35 kg / cm³;
• plastic grade of clay - 0.25 kg / cm ³;
• hard clay - 0.5 kg / cm ³.

Based on the developed project of the future structure, it is possible to determine what the total weight / weight of the house will be.

The approximate value of the specific gravity of each structural element:

• a brick wall with a thickness of 120 mm, that is, half a brick - up to 250 kg / m²;
• a wall of aerated concrete or 300 mm foam concrete blocks of the brand D600 - 180 kg / m²;
• a wall of logs (diameter 240 mm) - 135 kg / m²;
• 150 mm wall of timber - 120 kg / m²;
• 150 mm frame wall (insulation is required) - 50 kg / m²;
• attic from wooden beams with obligatory warming, density reaching 200 kg / m³ - 150 kg / m²;
• hollow concrete slab - 350 kg / m²;
• interfloor or basement of wooden beams, insulated, density reaches 200 kg / m³ - 100 kg / m²;

• monolithic reinforced concrete floors - 500 kg / m²;
• operational load for overlapping interfloor and socle - 210 kg / m²;
• with a roof made of sheet steel, corrugated metal or metal tiles - 30 kg / m²;
• operating load for ceiling attic - 105 kg / m²;
• with a roofing double-layer of roofing material - 40 kg / m²;
• with a roof of ceramic tiles - 80 kg / m²;
• with slate - 50 kg / m²;
• snow load type applied to the middle zone of the Russian territory - 100 kg / m²;
• snow load type for the northern regions - 190 kg / m²;
• snow load type for the southern part - 50 kg / m².

The area of ​​the whole plate should be calculated based on the engineering project.The weight of the building should be divided by the area to get the specific load indicator acting on the ground surface. By the way, the result does not take into account the foundation mass. Next you have to compare the resulting figure with the optimal concentrated load, then you can calculate the difference, that is, find out how much is not enough to obtain the optimum value of specific pressure. The resulting difference must be multiplied by the area of ​​the plate itself, in order to obtain the necessary foundation mass as a result.

Then the result of the mass of the foundation plate is divided by the density of reinforced concrete 2500 kg / m³. Thus, they will get the required volume of the base plate. This volume must be divided by the value of the area of ​​this plate to get its thickness.

The resulting thickness should be rounded to the nearest largest or, on the contrary, the smallest value, which is a multiple of 5 centimeters. According to the already rounded values, it is necessary to recalculate the weight of the foundation, adding the number with the mass of the building to determine the calculated specific pressure acting on the ground surface. Next, you should compare the result with the optimal.It is important to remember that this difference cannot exceed ± 25%.

The specific type of load of the total weight of the structure affects the concrete below. Based on this, it is necessary to determine the optimal grade of concrete that will be used for casting, with the condition that the strength of the concrete pavement will remain in compression, that is, to calculate for punching. Basically, the choice is between the brands M300, M200 and M250.

In fact, such calculations are considered simple. Here you will need only the knowledge acquired at school in mathematics lessons.

To learn how to build and calculate a monolithic foundation, see the following video.