How to calculate the dimensions of the foundation. Strip foundation - do-it-yourself calculation and construction What are the dimensions of the foundation for the house

How wonderful to have your own home! In order to save on construction costs when building a house of a large area, the construction of a two-story house may be a profitable solution, since the minimum part of the site will be involved in the construction. For the construction of a two-story building, it is imperative to carry out geodetic studies. They are necessary for the correct determination of the groundwater level at the construction site of the future building and the quality of the soil. Naturally, when carrying out construction work, the main emphasis is on calculating the dimensions of the most important structural part of the structure - the foundation. This calculation must be extremely accurate! Initially, the width of the foundation for a two-story house is calculated, as well as its depth and the area of ​​\u200b\u200bthe sole. It is the foundation that takes on the entire load above and distributes it over the entire base of the structure.

The choice in favor of the tape type foundation

Based on construction practice, it is not profitable to build a building on a pile foundation. Its construction will require significant financial investments not only for the transportation of the piles themselves, but also for the rental of special equipment, etc. Therefore, for brick houses with several floors, strip bases are most often used.

If a prefabricated foundation is used, then it consists of wall blocks made of concrete and reinforced concrete slabs, 0.5 meters thick. A special expansion is provided below, which prevents its displacement by soil. Narrow elements are necessarily reinforced, and PVC film and insulation are placed at the points of contact between the brick walls and the base.

Most often, for such houses, flood foundations are made, which are made of concrete with crushed stone or gravel. First, the formwork is set, and then the concrete is poured and compacted.

Calculation of the width of the foundation tape

Before starting the preparatory work, you should ask yourself what width of the foundation will be required during construction. Focusing on the quality characteristics of the entire building as a whole, the width of the sole is calculated. For a brick two-story house, the tape deepens 0.3 meters below the freezing line. But for a wooden one, it is 0.1 meters less, in the absence of uneven swelling of the soil.

What is the width of the foundation strip? The tape strip itself is usually 400 mm, which is quite enough. After that, the area of ​​\u200b\u200bthe strip foundation is calculated. The area of ​​\u200b\u200bthe structure depends on this indicator, at which the built two-story house will have maximum stability.

Below is the formula by which you can calculate the area of ​​\u200b\u200bthe sole:

S > k(n)*F/k(c)*R,

• k (n) – reliability coefficient,
• k (c) - coefficient of working conditions,
• R - soil resistance.

The most important rule is to prevent the structure from sagging under the exerted loads, since in the case of heaving of the soil during frosts, the building can be pushed out, or vice versa, go into it under its own weight or snow. Incorrect calculation of loads can lead to the fact that the newly built house collapses.

Parameters Used

When calculating the width of the base of the foundation, do not forget about the following parameters:

• bearing capacity - this parameter is necessary when calculating the area of ​​\u200b\u200bthe sole in order to properly dig a pit. The calculated width of the strip foundation must be consistent with the bearing capacity;
• the thickness of the bearing wall - with correct calculations, it turns out at least 0.1 meters less than the thickness of the base. This is enough to ensure that there is a possibility of high-quality finishing of facades;
• the distance between the reinforcing bars, which must be at least 200 mm.

Loads taken into account in the calculation

How to determine the entire load acting on the strip foundation? Many parameters need to be taken into account. These are the specific gravity of walls, roofs, ceilings, and foundation loads, and loads from snow, etc. If the numerical values ​​of these loads are known, then their total load can be calculated without any problems.

For example, we will use the tabular values ​​​​of the average specific gravity: for a slate roof - 40-50 kg / m2, for roofing material - 30-50 kg / m2; tiled - 60-80 kg / m2; sheet steel - 20-30 kg / m2. The value for brick walls is 200-270 kg / m2; for reinforced concrete - 300-350 kg / m2; for wooden - 70-100 kg / m2; for frame with insulation - 30-50 kg / m2. In order to calculate the load for reinforced concrete floors, 500 kg / m2 are taken, and beams - from 70 to 300 kg / m2.

Snow loads are calculated on the basis of regulatory data, focusing on the climatic zone. In the middle climatic zone, the specific load is equal to 100; in the north - 190; in the south - 50. These values ​​​​are multiplied by the area of ​​\u200b\u200bthe roof.

The width of the sole is also affected by the load from the foundation of the object under construction. To more accurately calculate this parameter, you need to know the mass, area and volume of the foundation. These are quite complex calculations, so the width of the tape is assumed, with an inner side of 400 mm. If we calculate the product of the average density of the material from which the foundation is made (for reinforced concrete - 2400) and the volume of the base, it is possible to calculate the load value. All the parameters obtained must be summed up and substituted into the formula, thereby you can get the value of the area of ​​\u200b\u200bthe foundation of a two-story house.

Sole Size Calculation

It is imperative to take into account the pressure on the support, so that the calculated value is greater than the average. During the calculations, one should not forget about the characteristics of different types of soil, and about the structures of the building, and about the depth of laying the foundation. The maximum rate of precipitation and rises of the soil itself is also taken into account. The structures are additionally strengthened so as not to subject the foundation to vertical deformation, while observing all the requirements for technology and architecture. If the soil at the construction site is clayey, possibly with a high content of peat, or subject to seismic loads, then the platform should be provided with good strength and solidity.

Many experienced builders advise laying the foundation intermittently. Thus, its sediment is several times less than that of the tape, and this accordingly increases the pressure under the sole by 20-30%.

So what is the estimated width of the strip foundation?

The more complex the structure of the house and the heavier the building materials used in construction, the greater the pressure on the foundation. And the width of the foundation directly depends on this value. So how wide should the foundation be to support the entire load?

Designers often independently calculate with a high degree of accuracy the optimal width of the foundation for the house, but for approximate calculations, in order to determine the required amount of work and associated costs, you can use the values ​​​​from the table.

1. Bath / barn (load up to 20kN / m2), concrete strip width - from 250 to 400 mm;
2. Wooden house (load 30 kN / m2), width is from 300 to 650 mm;
3. Two-story brick cottage, width can vary from 650 to 750 mm.

For heavy buildings, especially if they are built on loose soils, an extremely accurate calculation of the width of the foundation and an expert assessment of its bearing capacity are required. In order to avoid critical errors, it is not recommended to calculate on your own!

Whatever the construction, it should always begin with a project in which the leading engineers make calculations based on the climatic conditions of the construction area and the looseness of the soil. Since the width of the foundation, or rather its sole, can be expanded if the soil is loose, and made 200-300 mm to the top if winter frosts do not exceed -10 ○С. It is possible to additionally add bookmarks under the columns, this will save a lot on the foundation.

Thus, this article discusses the main points that should be remembered, they will help determine the main parameters for the construction of the foundation, such as - depth and width of the foundation for a two-story house. The information obtained will help to keep control over the process and keep abreast of all the questions asked during construction by experts and specialist designers.

Calculating the size of the foundation for the house is a painstaking work that requires attention, because the quality of the above-ground part of the house depends on its correctness. As a rule, there is a standard system, it was compiled by architects, it is quite simple and should not be used for houses of complex construction, as there may be some discrepancies. If you want to know how to do it right, read on….

The most basic task of each developer is to build a foundation that is durable and reliable, and in order for it to meet the requirements, they select the appropriate geometry. To make it easier to calculate, look at the finished foundations that are ideal for your architectural plan. It is worth paying attention to the shape, quality and defects. They will point out to you what mistakes were made at the time of construction.

Options

After a visual acquaintance, you can safely proceed to a full-fledged calculation, which includes the values ​​\u200b\u200bof the bearing capacity and the deformation of the soil in the area where the foundation will be built. This requires knowledge of mathematics and physics.

The calculation of the bearing capacity is not complicated, it is difficult to deform - it should be done with professionals.

Take, for example, a strip foundation. The following data will be required:

1. Soil quality.
2. Level of ground water leakage.
3. Ground freezing mark.
4. Architectural project of the house.

Having objective data, you can proceed to the phased calculation of the foundation.
The first stage is the determination of the weight of the external structure of the house, which is above the ground, including the additional load from furniture, decorative finishes, etc., which will produce a specific pressure on the sole soil.
The second stage is geometry.
The third stage is adjustment.

How to determine the size of the foundation for an economy class house?

For this type of house, it is necessary to determine:

• the specific gravity of the external structure, located above the base of the foundation, while taking into account the weight of the soil itself;
• plinth, including decorative trim, floors and floor slabs;
• wall panels, excluding door and window openings;
• partitions with external and external finishing. A similar calculation is made directly with the walls;
• truss system and ceiling, including trim and roofing material;
• flights of stairs;
• insulating layer.

You will need a drawing paper, on which you will need to sketch all the structural elements of the house. The sketch should be as similar as possible to the real design. At the end of the sketches, the volumes of the structure are determined according to the formula - LxHxW = V. If it is necessary to determine the volume of a complex structure, then it is necessary to divide the foundation into parts and calculate their volume according to the proposed formula. The result is multiplied by the weight of the construction material. As a result, the weight of the structural element will be known, it must also be determined.
To find out the weight of the material, you need to multiply the resulting weight according to preliminary calculations by the load safety factor.

The safety factor depends on the nature of the load.

At the end of the summation of the weight of all structural elements, the weight of the whole house should be obtained, in the sketch it is designated - "Rk". The dimension of the weight of the house is indicated in tons or kilograms.

1. The determination of geometric parameters is carried out taking into account the deepening of the foundation, the parameters of the house plan, material, soil classification, as well as the planned structure.
2. According to the final calculations, a diagram and a sketch are drawn up, where the width of the structure depends on the category of soil. It should be noted that the width of the soil, regardless of what soil it is arranged on, should not be less than 350 mm and less than the width of the walls of the house.
3. The height of the house depends on the amount of foundation immersion in the ground.

To determine the snow load on the roof of a house, a standard formula is used - Correction factor X per Pc, resulting in an updated snow load Pc *.

Video

We offer you to watch a video about the errors of laying the foundation:

The concept of "foundation" means the support of the house. This is the lower part of the structure, which receives and distributes loads. Its strength is the key to the reliability of the building. Properly chosen size and thickness of the foundation guarantee good performance and durability of the structure.

Economic side

An unreasoned overestimation of the base mass leads to a higher cost of work, and an underestimation is fraught with unforeseen consequences. The task of design is to find a compromise between the cost of building and laying a solid foundation that can take the load from the weight.

Investments in the initial cycle are much higher for the construction of small buildings than multi-storey buildings. When building a brick house, strip foundations are more often used. Accordingly, the technologies used are the same as in industrial construction.

As a result, in comparison with high-rise buildings, the cost of 1 sq.m. It will be possible to reduce it with the correct selection of the foundation technology and its specific size.

What to prefer?

Concrete and stone foundations share:

• on massive ones - lying under the building;
• on tape;
• on poles - free-standing poles.

columnar

Suitable for houses without basements. Their advantage in comparison with others is efficiency. However, this type of foundation is not considered successful for buildings with basements and basements. Due to the danger of being shifted by the lateral pressure of the soil, they cannot be used in the presence of large differences in height.

Tape

This type is the most popular in the construction of private houses. Their width depends on how the soil can withstand the load and on its volume on the base. An important plus of these structures is that they tolerate it well and have excellent bearing capacity.

In the private sector, shallow strip foundations are used more often. When laying them, prefabricated blocks, a concrete monolith or rubble stone are used.

For buildings without basements, it is better to build a prefabricated tape type. The presence of a huge number of joints between parts must be waterproofed, and this is a waste of time and labor.

Monolithic ones are laborious, but they create complete waterproofing, which is necessary when laying a house with a basement. When building an individual cottage, they are more economical and cost one and a half less than prefabricated ones.

The monolith does not require additional waterproofing of the seams, significantly reducing the complexity and costs of the initial stage. In addition, the monolith is more resistant to heaving in frost and subsidence of the soil.

With increased soil moisture, waterproofing of buried parts is an obvious problem that can increase the cost. A monolithic foundation practically does not allow moisture to pass through, and when special additives are added, its cost is lower than when using a special type of waterproofing.

Slab

They are suitable for houses if the indicator of water in the soil is too high. According to the size of the house, a single monolith is laid, reinforced with a frame. Due to the increase in the interaction between the foundation and the base, the probable subsidence of the soil is reduced.

Pile reinforced concrete

The piles are lowered into the ground with the help of vibrators. The piles pass through the upper, looser soils and transfer the load to the denser layers. Deep layers are compacted, increasing the bearing capacity.

bored

In fact, these are wells laid with concrete reinforced with a reinforcing cage. In this case, the formwork is soil drilled to a depth of up to 1.5 meters and a width of up to 250 mm.

Types of bored piles:

• piles without additional strengthening of well holes for dry soils;
• stuffed piles with overpressure reinforcement for weak and flooded soils;
• stuffed piles with strengthening of wells with casing pipes for fragile soils.

Screw piles

These are large screws driven into the ground. This type is suitable for houses on weak soils with high waters, for quicksand. With this technology, minimal earthworks are performed.

Load bearing capacity

The first few years after the completion of a building, the soil compresses under the weight of the house. Under the influence of showers and floods, the foundation sags, causing cracking and destruction.

The bearing capacity and size are determined taking into account the characteristics of the soil and the width of the base. For example, a columnar foundation with a circumference of 25 cm rests on soil with an area of ​​490 sq. cm.

If the bearing capacity is 2.5 kg/sq. see (medium dense sands), then the foundation is able to transfer it (including the thickness of the columnar foundation for building a house) up to 1225 kg.

A dense clay base of the same size is capable of carrying a load of 490 x 6.0 = 2.94 tons.

Strip foundation (width - 40 cm and length - 28 m) with the dimensions of the foundation for an individual house 6 x 8 sq.m. requires a base of 112,000 sq.cm.

With the same bearing capacity of the soil, the base can take the following loads: 112000 x 2.0 = 22400 kg, i.e. 224 tons and 112,000 x 6.0 \u003d 672,000 kg, that is, 672 tons, respectively. These are data for sizes from 1.5 to 2 meters deep, with a width of the base of the foundation from half a meter to 1 sq.m.

As the depth increases, the bearing capacity increases. And at higher numbers, it decreases due to the lower density of soils.

When calculating the width and bearing capacity of the foundation for the house, it is taken with a certain surcharge. In practice, this percentage is about 30. To create a margin of safety, the load is increased. This covers possible inaccuracies in preliminary calculations.

If you reduce the margin, there may be a threat of drawdown (especially in the initial period of operation). If it is increased, the cost of construction increases.

Base loads:

• size and weight of building materials;
• specificity and width of floors;
• type and size of materials for the roof;
• type of roof and its width;

How to determine the load

It depends on the specific gravity of the various components.

For foundations of different widths

For floors

For roofing

Also, with a full calculation of the load on the foundation, the coefficient of influence of the roof slope on the load in snow is determined. On average, it ranges from 1 to 0.2 (with a slope of 20 to 60 degrees).

When determining the mass of a building, internal partitions and walls resting on the floor, and additional loads of various equipment and inventory for different types of floors are taken into account.

For the final calculation of the thickness of the foundation being laid under the house, the values ​​\u200b\u200bof the loads of the building and the soil are taken. Then the area is calculated, and the optimal width of the foundation is displayed. Next, the wall thickness indicator and a margin of 10 centimeters for further finishing are taken into account.

An example of calculating the foundation of a tape type

After completing the calculations for the size of the house 6 x 9, the minimum value was 5 square meters. m. With a tape width of X, a total calculation is performed:

2 x 9 x X + 2 x X (6 - 2X) = 5

18 X + 12 X - 4X ^ 2 = 5

It turns out X1 \u003d 0.17 meters

X2 = 7.3 meters.

That is, in this case, the minimum allowable value of the tape is X1 = 0.17 meters.

The resulting value is very relative and if the width of the wall of the house is assumed to be 30 cm, then taking into account the additional dimensions of 10 centimeters for finishing, it turns out 40 cm. Thus, the base stock will be equal to

0.4: 0.17 x 100mm - 100mm = 135%.

Whatever construction begins, it should be based on a project developed by specialists in compliance with all mandatory norms, sizes and accurate calculations.

The construction of a house begins with the construction of the foundation. The strength and durability of the house built on it will depend on the quality of the foundation. The cost of this lower part of the future building is about a quarter of the total cost of the house. In addition, this is a time-consuming process and requires a clear understanding of its ultimate goal. Errors made in the calculations and in the construction of the foundation will cost, if they are corrected, very expensive. Often the sums for reworking a marriage even exceed the initial costs. It is possible to avoid mistakes during the construction of the foundation only by its competent calculation and execution.

The strip foundation is universal. This type of foundation is suitable for houses with any wall design.
In cross section, the strip foundation of the house forms a rectangle located vertically. The upper part of this rectangle should take into account the slope of the construction site and protrude with its edge approximately 100 mm above the plane of the adjacent ground surface. In addition, the upper edge of the foundation, depending on the design of the walls of the house, may be wider than the thickness of the wall.

During the construction of a residential building of 1-3 floors, the transverse dimensions of the strip foundation usually do not differ much. This can be explained by the fact that the loads from the house on the ground are insignificant, while the area of ​​\u200b\u200bthe base of the foundation will always be more than necessary by the calculation by about 2-3 times.

So, depending on the material used in the creation of the strip foundation, the average width for rubble foundations is 600 mm; for concrete or reinforced concrete and rubble concrete 400-600 mm; for foundations made of bricks - this is 500-550 mm. Such a width of the base of the strip foundation ensures the dressing of the vertical seams of stones and is convenient in work, reducing unnecessary labor costs.

If the soil at the construction site is weak or heterogeneous, then most likely the pressure of the house with its weight on such soil will exceed the norm (for central Russia it is 1-1.5 kg / cm²). In this case, it is necessary to increase the width of the sole of the foundation. This can be done by creating ledges along the height of the foundation every 300-600 mm. In addition, it is possible to create a “cushion” in the lower part of the foundation by placing a reinforced concrete slab or compacting coarse sifted sand, with grains of sand 1-2 mm in size, with a layer 200-300 mm thick.

Terms, definitions and parameters for calculating a strip foundation for a house

Foundation- the lower part of the house, located underground, designed to transfer and distribute the load from the building to the ground.
Foundation sole- foundation plane directly interacting with the ground.
Foundation depth- the distance from the base of the foundation to the surface of the soil.
Underlying soil layer (base)- the layer of soil on which the sole of the foundation rests.
Estimated depth of soil freezing- the position of the freezing boundary relative to the ground level, taken as a design value (SNiP standards).
Ground water level- the position of the groundwater table relative to the ground level in a conditionally open pit (well).
Compressible soil thickness- deformable part of the soil, perceiving the load from the foundation.

The procedure for calculating the strip foundation for the house

Determining the depth of the strip foundation

The depth of the foundation depends on the depth of soil freezing, the level of groundwater and the underlying soil layer. Usually the depth of the foundation is chosen below the freezing depth, but not less than 500 mm.

The depth of freezing is determined by the climatic conditions of the region and corresponds to the highest value of freezing of wet soil without snow cover at the lowest recorded temperatures. It can be determined from the table:

In addition, it should be borne in mind that with year-round living in a house, when in winter it warms up due to heating, the estimated depth of soil freezing decreases by 15-20%.

Also, the estimated depth of soil freezing can be determined by the formula:

df=kn× d fn,

kn- the coefficient taking into account the influence of the thermal regime of the structure is taken according to table 1 of SNiP 2.02.01-83 Foundations and foundations;
dfn- the normative depth of seasonal freezing of the soil is taken according to the climate map "Zoning the territory of the Russian Federation by the mass of snow cover".

When calculating the depth of the foundation in relation to groundwater, they strive to ensure that the base of the foundation transfers the load to a solid layer of soil. Such a layer is located above the groundwater level, which depends on the geological conditions of the area where the construction site is located.

When calculating the depth of the foundation, taking into account the presence of structural features of the house, the depth of the basement is also taken into account.

Thus, the depth of the foundation is equal to the maximum value, consisting of values ​​calculated from climatic (depth of soil freezing), geological (depth of groundwater) and structural (presence of a basement) features.

Calculation of the dimensions of the sole of the foundation

Determination of geometric parameters, the main of which is the area of ​​​​the base of the foundation, is also a critical stage in the calculation. Since the reliability of further operation of the house depends on the correctness of its definition. If the support area turns out to be less than necessary, then this will entail an uneven subsidence of the structure and its deformation. Excess area of ​​the sole of the foundation is an unjustified additional cost.

There are two options for calculating the area of ​​the base of the foundation by limit states. The first version of the calculation is based on the bearing capacity of the foundation, the second is on the allowable deformations of the structure.

Calculation of the dimensions of the base of the foundation according to the bearing capacity of the base

It consists in assessing the stability of the underlying soil layer to the effect of the weight of the structure. Under the influence of operational loads due to the compaction of the foundation soil, a deformation shift of the soil layers occurs and the foundation settles. The depth of settlement depends both on the strength of the base soil and on the magnitude of the force pressing on the soil. There is a formula for calculation:

S>ϒnF/ϒcR O ,

Where:
S- the area of ​​\u200b\u200bthe sole of the foundation (cm 2);
F- design load on the base (total weight of the house with additional operational load) (kg);
ϒ n - reliability coefficient (equal to 1.2);
ϒ c - coefficient of working conditions;
R o - conditional design soil resistance of the base for the foundation.

The total weight of the house with additional operating load is the sum of the values:

• the mass of the walls of the house with gables and with internal partitions;
• the mass of the basement and interfloor ceilings;
• roof weight, taking into account the roofing material and snow load.

There are convenient online calculators for calculating the weight load on the foundation that you can use. For an approximate calculation of the total weight of the house, you can use the table:

The coefficient of working conditions has the following values:

The conditional design soil resistance of the foundation for the foundation is determined from the tables:

Calculation of the dimensions of the base of the foundation according to the permissible deformations of the structure

Unlike the first option for calculating the area of ​​​​the foundation, this option allows you to exclude deformation of the house structure from uneven subsidence of the foundation. This is ensured by assessing the compliance of the actual and permissible level of deformation of the structure from the impact of operational loads.

There are the following types of structural deformations of structures:

Deflection and camber- occurs due to uneven subsidence of the base of the foundation.

occurs when the foundation settles on one side.

occurs when a structure has a high flexural rigidity (high-rise structure or element).

skew- occurs when the foundation is unevenly settled in one of the sections.

Horizontal offset- occurs in foundations, in basement walls, in retaining walls in areas loaded with horizontal forces.

Permissible values ​​of deformations of structures depend on the design features and materials used in construction are given in the table:

Relative irregularity of settlement - the maximum ratio of the difference in the settlement of two sections of the foundation to the distance between them. Based on this value, it is possible to determine the minimum value of the distances between sections with uneven settlement, and determine the estimated area of ​​​​the foundation base.

Example:

Suppose that a two-story brick house is deformed in the form of a deflection in the center by 1 cm.

The distance along the length of the foundation between the measurement points of the deflection section is 600 cm. With a building length of 12 m, the relative unevenness of the settlement is 1/600=0.0017. The permissible unevenness of the settlement of such a structure according to the table is 0.002. Therefore, a draft of 1 cm is acceptable.

Plinth height calculation

The height of the basement is calculated taking into account the climatic characteristics of the area of ​​the construction site in terms of the amount of snow cover and the necessary characteristics of the rigidity of the cross-section of the foundation.

Calculation of the amount of materials and the total cost of the strip foundation

Calculation of reinforcement for a strip foundation

Reinforcement of the strip foundation is necessary to increase the resistance to deformations and operational loads of the structure. To reinforce the foundation, you will need to calculate the diameter and number of reinforcement rods.

From practice and technical documentation it follows that the amount of reinforcement should be at least 0.1% of the cross-sectional area of ​​\u200b\u200bthe base.

Rebar diameter calculation:

1. For light structures - 8 mm.
2. For medium structures - 10-12 mm.
3. For heavy buildings - 14 mm.

Calculation of the number of reinforcement bars:

1. To calculate the total footage of horizontal bars, it is necessary to multiply the perimeter of the entire foundation by 4.
2. To calculate the number of jumpers, it is necessary to divide the total length of the foundation by the planned length between the jumpers and also multiply by 4.
3. If the foundation is deep and provides for two frames, then in the calculations all the results are simply doubled.
4. When calculating the number of bars, one can proceed from the standard length of reinforcing bars - 6 m.

Example:

For a strip foundation for house 6× 8 m with two partitions of 6 m and 4 m each has a perimeter of (6+8)×2 \u003d 28 m. Taking into account the partitions, the total perimeter will be 28 + 6 + 4 \u003d 38 m. So the total footage of the reinforcement will be 38 × 4 \u003d 152 m. Taking into account the length of the reinforcing bar - 6 m, an 8 m section will need another 2 m of the rod, for which the remnants of a 4-meter partition are suitable. Thus it turns out (4 + 4) X 2=8 joints. Taking into account the overlap of the rods at the joints of 0.5 m in both directions, 152 + 8 = 160 m of reinforcement will be needed. In pieces, this will be 160/6 \u003d 26.6, rounded up to 27 pieces of reinforcing bar. For lintels with a knitting distance of 0.5 m, with a foundation length of 38 m, for vertical and horizontal rods you will need 38 / 0.5 ×4=304 pieces. With a frame height of 0.5 m and a width of 0.25 m, 304/2 ×0.25=38 m, and on the vertical 304/2 × 0.5 = 76 m of reinforcing bar. The number of rods per jumper is obtained (38 + 76) / 6 = 19 pieces.

Calculation of concrete on a strip foundation

To calculate the amount of concrete for the construction of a strip foundation, there is a simple formula:

TO bΣ= W f× IN f×( D 1+D 2),

TO bΣ - the required amount of concrete;
W f - the width of the foundation;
IN f - the height of the foundation;
D 1 - the length of the inner side of the structure;
D 2 - length of the outer side of the structure.

Calculation of the cost of strip foundation

To calculate the cost of a strip foundation, it is necessary to clarify the current prices for the materials used and multiply by the values ​​\u200b\u200bobtained in the calculations described above.

Concrete will cost the most. Its cost will be 25% of all foundation costs. Then from 15% to 20% of the costs, depending on the size and quality, will go to the fittings. Formwork will require 10% of the total cost. Further 5% of the cost is transportation costs. Other, not the smallest 40-45% of the costs will require sand, knitting wire, waterproofing material, brick, fasteners, tools, etc.

There are also convenient online calculators for the full calculation of the strip foundation and videos with detailed instructions.

Related videos

Structural for reinforced concrete beams, the minimum width is allowed 15 cm, and for shallow strip foundations (which are free-lying beams on an elastic foundation), a width of at least 25 cm for light garden buildings, and a width of at least 30 cm for country houses. The width of a strip shallow foundation cannot be less than the width of the wall supported on it.

However, in addition to structural limitations, there are also requirements set by bearing capacity of soils under shallow strip foundations. The specific load from the building per unit area should not exceed 70% from the bearing capacity of the soil. You can regulate the amount of load using the area of ​​\u200b\u200bsupport of the foundation on the ground. The larger the support area, the lower the specific load transferred to the ground.

Approximate calculation method for the minimum sufficient width of a shallow strip foundation. This method for determining the minimum sufficient width of a shallow strip foundation is based on the idea that the value of the specific load per unit area of ​​the soil under the foundation should be less than the bearing capacity (calculated base resistance) of the soil under the foundation. The difference between the load from the house and the bearing capacity of the soil must be at least 30 percent greater in favor of the bearing capacity of the soil (factor of safety for concrete structures cast on site with a specific weight of less than 1600 kg/m3). In order not to tire the most impatient readers, who are finally in a hurry to find out without too much sentimentality the minimum sufficient width of a shallow strip foundation, we publish a table based on data from the British State Building Code Building Regulations Approved Document A: 2010, 2E3, Table No. 10. The British Architectural Office calculated everything for us in advance, and we tried to average and adapt the presented data a little to make the data presentation more convenient:

Now, the most adventurous and less curious readers can run to cast their shallow cast-in-situ strip foundation, and the rest can find out how the British got this data and make their own more accurate calculation for their own home, so as not to get into a mess.

To determine the minimum sufficient width of a shallow-depth strip foundation based on the bearing capacity of the underlying soils, it is necessary to solve the equation:

Dead weight of the building is the sum of the weights of all the building elements of the house structure. To calculate them, you need to use the following tables:

Table No. 6Load from 1 m 2 spans up to 4, 5 m

Table number 7Table of the amount of timber in m 3 lumber

Table No. 8Table of the number of boards in a cubic meter of lumber

Table No. 9Tableroofing weight values

Table No. 11 Load from 1 m 2 of the horizontal projection of the roof