The soil has the most direct influence on both the type of foundation and its depth.
Laying depth columnar or pile foundation It makes no sense to calculate, as a rule, pillars (piles) are laid below the freezing depth by 30-40 cm, but always on solid ground.
The slab foundation is laid to a depth that depends solely on the thickness of the monolithic slab.
It remains to figure out the depth of the strip foundations, depending on the type of soil. Calculation of the depth of such a foundation is made based on the recommendation table:
Calculation of the foundation based on the bearing capacity of the soil (we calculate the required support area)
It is very simple to calculate the foundation based on the bearing capacity of the soil, despite the apparent complexity and large volume. The whole calculation comes down to determining the minimum area of the foundation for the house, at which the soil will easily support the entire mass of the house, but still, so as not to get confused, let's talk about everything in order.
The formula itself for calculating the minimum area of the foundation base is as follows:
What does this mean? It's simple, we calculate using the formula minimum area foundation supports on the ground, real area the support should be larger than the calculated one, how much more depends on the desire and ability of the developer to provide a safety margin.
Now let's figure out where we can get all these scary values from the formula to calculate the area of the foundation.
Working conditions factor γ c
The operating conditions coefficient can be taken from this table:
| Priming | Soil type | Coefficient |
| Sands | Large, flexible and rigid long structures | 1,4 |
| Small, any structures | 1,3 | |
| Large, rigid, long structures | 1,2 | |
| Clay | Low plasticity, non-rigid and rigid short structures* | 1,2 |
| Plastic, non-rigid structure structures (wooden), rigid structure long** | 1,1 | |
| Plastic, rigid wall construction (brick) | 1,0 |
* - short buildings with a length to height ratio of less than 1.5
** - long buildings with a length to height ratio of more than 4
Calculated soil resistance under the foundation R0
Since the mass of the entire house will rest almost entirely on the soil under the foundation, it is necessary to know the calculated resistances of various soils at a depth equal to the depth of the foundation.
If the foundation is planned to be deepened by 1.5 m or more, then the calculated soil resistance can be taken directly from the tables.
Table for gravel soils and sands:
Very often we have clay soils on our site. For clay soil The calculated resistance can be taken from this table:
These tabular data can be directly used in the case of laying a foundation to a depth of 1.5 m or more. In cases where the foundation is laid to a shallower depth, the density of the soil under the base of the foundation will differ, and therefore the calculated soil resistance will also differ.
How to calculate the mass of a house with a foundation F
Of course, it will be practically impossible to calculate the absolutely accurate mass of the entire house; the mass of the house will constantly change throughout the year. So, for example, in winter the house will be heavier due to the snow on the roof, which also ultimately rests on the foundation of the house.
But it is not difficult to calculate the approximate weight of the house, with all the additional loads, especially since some values are taken approximately with a maximum margin.
What is taken into account when calculating the mass of a house
When calculating, everything that rests on the foundation is taken into account, namely:
- the full load of the structure, including the mass of walls with finishing, floors, roofing, as well as the foundation itself
- maximum load from objects in the house that transfer weight to the foundation of the house (stairs, fireplaces, interior objects, etc.)
If your ground floor floors are poured on the ground, their load can be ignored. You can also not take into account the load from objects located on such a floor (furniture, people, etc.).
Determining the mass of the walls
Each building material has its own specific gravity, measured in kilograms per cubic meter. For example, reinforced concrete has a specific gravity of 2500 kg/m3, which means that one cubic meter of concrete weighs 2500 kg.
In SNiP II-3-79 “Construction Heat Engineering” in Appendix No. 3 “Thermal Indicators of Building Materials and Structures” you can find the specific gravity of basic building materials, but these SNiPs are from 1979, since then many completely new materials have appeared on the construction market. In this regard, it is physically impossible to write the specific gravity for each, and even such an accurate calculation for an individual low-rise residential building, which takes into account the weight of mortar joints, nails, staples, etc. – inappropriate.
On the Internet you can easily find the specific gravity of any material you are interested in, but if you have already 100% decided what you will build your house from, then you can check the specific gravity with the manufacturer or seller.
For approximate calculations, you can use a table that shows the weight of one square meter of wall (do not confuse it with specific gravity), and you will only need to calculate the total area of all your walls and multiply by the value from the table.
Table of weight per square meter of wall with a wall thickness of 15cm.
The area of the walls is counted together with window openings, i.e. We simply multiply the height of the wall by its length without subtracting the openings. This is necessary for a safety margin in the calculations.
We calculate the specific gravity of floors
In order not to calculate the mass separately for each flooring material, you can use an approximate table that shows the approximate specific weight of one square meter of flooring; in order to calculate the total weight of the entire floor, you need to multiply its area by the data from the table.
This table has already taken into account with a reserve the load from household objects located on the ceiling, so it is not necessary to additionally calculate how much the bathtub weighs and how much the refrigerator weighs.
Calculation of the specific gravity of the roof
To calculate the load from the roof, you need to know what material it will be built from, and you also need to calculate the roof area. Then multiply the roof area by the data taken from this table:
In addition to the load of the roof itself, the load created by snow will also act on the foundation in winter.
Calculation of snow load in winter
To calculate the snow load, we will need the data from the previous formula, namely the roof area, which must be multiplied by the data from the table:
Calculation of foundation weight
Why 2500? Because reinforced concrete has a specific gravity of 2500 kg per cubic meter.
Final calculation of the weight of the entire house
Now all the data needs to be added up, i.e.:
- wall weight
- floor weight
- roof weight
- snow load
- foundation weight
An example of calculating the total load of a house on the ground:
Don't worry if your calculations show completely different values and proportions. The table shows numerical values - taken from the head (approximate). There is no need to rely on them in your calculations.
Final calculation of the minimum area of the foundation base for a house
Let me remind you of the formula for calculating the area of the base of a foundation and give an example of calculating a simple foundation:
S > γ n F / (γ c R0)
γn - safety factor for safety factor, constant value equal to 1.2
R0 - the calculated resistance of the soil under the base of the foundation, taken from the table, let’s take it as an example equal to 2.5
F - full load of the house, from the last table we take the approximately calculated mass of the entire house, we have it equal to150,000 kg
γc - a coefficient depending on the soil and the structure itself, taken from the table at the top of the article, let’s take it as an example equal to 1.1
Now all that remains is to substitute all the values into the formula:
S > 1,2 · 150,000 / 1.1 · 2.5 = 65 454 cm 2
Let's round the resulting value to 66,000 cm2.
Don't worry about getting such a big scary value, don't forget that this is the minimum area value in cm 2, and to convert it to m 2 must be divided by 10 000 .
66,000 / 10,000 = 6.6 m2
What does this mean? Everything is very simple, the area of the base of the foundation for the house should be at least6.6 m2. More is certainly possible. It is even desirable that there be more, as they say - with a margin of safety. But less - by no means!
In order to calculate the base area of the strip foundation, it is enough to multiply the total length of the entire laid strip by the width. Those. let's say you have length of the entire tape is 50m, A width - 0.4m. Calculate the area of foundation support on the ground by multiplying 50*0.4 = 20m2. This suggests that our future foundation fits our design house with a large margin, almost three times. And this, in turn, means that the support area can be reduced. We will most likely not reduce the length, but it is quite possible to reduce the width.
When calculating a columnar foundation, the number of pillars is selected in this way, i.e. We know the support area of one pillar; we need the sum of the areas of all pillars to be greater than the calculated one. And the greater the safety margin, the naturally better it will be.
Let's summarize the calculation of the foundation
As you can see, a lot has been written, but this is not because of the complexity of the calculations, but because of the many different types of soils, building materials, etc. The calculation itself consists of finding values from tables and substituting them into the formula.
Of course, these are very rough calculations, but they already take into account a decent margin of safety, so the work done is quite enough to calculate the foundation for a low-rise private house.
In country house construction, a strip base is most often used, which is rightfully considered universal. You can build it without involving specialists yourself. The main thing is to carry out all the calculations correctly, including the required amount of reinforcement for the construction of a strip foundation.
A strip base is a monolithic closed reinforced concrete strip running under each load-bearing wall of a building. This type of foundation is most often used in individual construction, because has a good set of necessary characteristics and excellent price-quality ratio.
It distributes the load along the entire perimeter and prevents subsidence and deformation of the building due to the acting forces of soil heaving. Wherein . Some hobbyists do not consider it necessary to reinforce the foundation. But this process is of great importance.
After all, ultimately the strip base acquires the following properties:
- strength, reliability and durability;
- ease of installation;
- possibility of waterproofing reinforced rods.
Reinforcing steel frame is the strength skeleton of a concrete foundation
Therefore, to increase the service life of the entire building, reinforcement is indispensable. But the main thing is not only to correctly strengthen the foundation, but also to calculate it correctly.
Planning the foundation must be done with particular care, because in case of deformation, it can affect the entire building, and fixing it can be very difficult and expensive. You can calculate the amount of materials required for a strip foundation and rolled steel for it yourself, or you can use the online calculator service.
An example of calculating a strip foundation
To calculate the strip foundation, you need:
- calculate how much the house weighs without taking into account the foundation;
- determine snow and wind loads;
- choose the type of base.
- calculate the area of the foundation base, taking into account the bearing capacity of the soil.
Snow load can be calculated based on SNiP 2.01.07-85. Section 5 provides data for all areas. It is quite difficult to calculate the wind load of a strip foundation. You can use the simplified formula: (15 x h + 40) x S, where h is the height from the ground surface to the top of the building, and S is the area of the structure.
When calculating the weight of a building, it is necessary to take into account the approximate weight of furniture and equipment located in the room. For example, with a building mass of 13384 kg, a payload of 11340 kg, a snow load of 8820 kg, and a wind load of 4410 kg, the calculations will look like this. Summing up these data, we get the figure 37954 kg. You need to add 30% to it for errors. As a result, the total load on the base is 49340 kg.
In order to calculate a strip foundation, it is necessary to take into account its base length and sole area. So, if the length of the load-bearing wall is 30 m (3000 cm), then: 24670/3000 = 8.2 cm. This figure is the minimum width of the strip base. But it is necessary to take into account that the thickness of the walls should be greater than the width of the foundation.
In order to calculate how much concrete is required, it is necessary to multiply the length of the load-bearing wall by the amount by which the foundation must be laid and by the width of the foundation. So, if the foundation on sandy soil is laid to a depth of 0.5 m, the width of the foundation is 20 cm (0.2 m), the length of the load-bearing wall is 30 m, then the calculation will look like this: 30 x 0.5 x 0.2 = 3 m3.
All materials for the foundation must be purchased with a small margin of 10-15%
Reinforcement calculation
Next, you need to calculate how much material will be needed for reinforcing work. For example, the diameter of the steel rod will be 12 mm, according to the plan in the casting there will be 2 horizontal rods, and vertically, for example, the rods will be located in increments of 0.5 m. The perimeter is 27 meters. So, 27 must be multiplied by 2 (horizontal rods) and the result is 54 m.
We count vertical rods in a similar way: 54/2 + 2 = 110 rods (108 intervals of 0.5 m each and two on each side). To account for the rods at the corners, you need to add 1 more rod, it turns out 114. If we take the height of the rod -70 cm, we calculate the length of the material: 114 x 0.7 = 79.8 m.
The easiest way to calculate the reinforcement for a strip foundation is to use an online service - a calculator.
Formwork calculation
If the parameters of the boards are: thickness 2.5 cm, length 6 m and width 20 cm, then the calculation will be as follows. The formula calculates the area of the side surfaces: the perimeter is multiplied by the height of the casting, and then by 2 more (the fact that the internal perimeter is smaller than the external one is not taken into account): (27 x 0.2) x 2 = 10.8 m2. Board area: 6 x 0.2 = 1.2 m2, 10.8/1.2 = 9.
This means that as a result, 9 wooden boards are needed, the length of which will be 6 m. A small number of connection boards is added to this number(at the discretion of the builder). As a result: you will need 134 m of reinforcing materials and 27 linear meters of wooden blocks 20 cm wide. The example did not take into account the number of fasteners. The received data is rounded.
Calculation of reinforcement for a floor slab can also be done using an online calculator.
Reinforcement scheme
On a strip foundation, more longitudinal tensions appear than transverse ones. Therefore, you can choose rods with a smooth surface as transverse rods, and corrugated ones as longitudinal rods. The corners bear the most loads. Therefore, when reinforcing them, it is necessary that one end of the rod goes into one wall, and the other into the other.
The reinforcement process should begin with the installation of formwork. The inside should be lined with a layer of parchment. The main purpose of the formwork is to facilitate the removal of the structure. The task of the frame is to uniformly distribute all loads on the base.
Its scheme is simple:
- Steel rods equal in length to the depth of the foundation are driven into the bottom of the trench. It is necessary that there is, on average, 50 mm from the formwork in increments of 400-600 mm;
- install stands (80-100 mm);
- 2-3 threads of the bottom row of rods are attached to them. For stands, you can use bricks, placing them on the edges;
- at the top and bottom the rows are secured with transverse jumpers to the vertical pin;
- the places where they intersect are fastened with viscous wire or welding.
When calculating and constructing a strip foundation, it is recommended to take into account the requirements of SNiP so that the structure is strong and durable
Welding work contributes to overheating of the metal and entails a change in properties. The thickness of the rods in such places also decreases. That's why Wire is often used for knitting. After reinforcement, it is only necessary to make holes for ventilation and fill the trenches with concrete mortar.
Cost of fittings
Reinforcement can be purchased at construction stores. Its quantity is calculated in linear meters. Therefore, in order to find out how many meters are required and calculate the final price, necessary rolled weight table. Next, we calculate using the formula: (number of metal rods in running meters) and multiply by (weight of 1 running meter of rods for the corresponding diameter) multiply by (cost of 1 ton of rods)/1000.
The weight of the reinforcement depending on the cross-section can be seen in the table:
| Reinforcement diameter | Kilogram in 1 meter | Meters to kilograms | Meters in 1 ton |
| Armature 5 | 0,187 | 5,347 | 5347 |
| Armature 6 | 0,222 | 4,5045 | 4504 |
| Armature 8 | 0,395 | 2,53165 | 2531 |
| Armature 10 | 0,617 | 1,62075 | 1620 |
| Armature 12 | 0,888 | 1,12613 | 1126 |
| Armature 14 | 1,21 | 0,82645 | 826 |
| Armature 16 | 1,58 | 0,63291 | 633 |
| Armature 18 | 2 | 0,5 | 500 |
| Armature 20 | 2,47 | 0,40486 | 405 |
| Armature 22 | 2,98 | 0,33557 | 335 |
| Armature 24 | 3,85 | 0,25974 | 260 |
| Armature25 | 4,83 | 0,20704 | 207 |
| Armature 28 | 6,31 | 0,15848 | 158 |
Reinforcement with a diameter of 12 mm and a corrugated or smooth surface is in great demand. It can be sold in rods and coils.
The approximate price for 12 mm diameter per 1 m can be found in the table:
| Name | Price per meter, rub |
| A1 12 mm | 21,78 |
| A3 A400 12 mm | 21,05 |
| A3 A500S 12 mm | 21,05 |
| A3 25G2S 12 mm | 22,98 |
| 35GS 12 mm | 22,7 |
Reinforcing a strip base is not at all difficult, although it is a fairly energy-intensive process that requires financial investment. But saving doesn't make sense. By choosing the right reinforcement and calculating its quantity, you can strengthen the foundation, while extending the life of the entire building.
You can watch an example of independent calculation of a strip foundation in the video:
A strip foundation for a house made of foam blocks, gas silicate or brick is one of the most common options. It works great on stable soils and allows you to organize a full-fledged basement in the basement. But for the construction to be truly durable, everything must be done with high quality.
When ordering turnkey construction, you can simply rely on the calculations of the company’s managers, without going into too much detail. But it’s still worth roughly estimating the amount you’ll spend on building materials and services. To do this, you will need at least a schematic drawing of the future monolith with all the dimensions marked, as well as an online calculator for more accurate calculations.
Initial data
If you have a strip foundation in your house design, to calculate it you will need to not only determine the length and width of the monolith, but also the height, dividing it into an underground and above-ground part (basement). This will allow you to find out the depth of the trench and include prices for excavation work in the estimate. The diagram should also show all the lintels on which the internal walls of the house will rest. If the project has a heavy stove or brick fireplace, you will also need to pour a concrete bed under them.
Correctly drawn base geometry also makes it possible to determine the costs of auxiliary materials:
- The area of support and contact with the ground in the underground part corresponds to the dimensions of the waterproofing.
- The squaring of the side surface of the tape on the outside is necessary in order to find out the amount of insulation; adding to it the area of the internal walls, we get the formwork consumption.
Another important point is the brand of concrete. Here you already need to know the weight of the building and the operational loads that affect the strip foundation. After conversion to units of support area, you will receive the required value in kgf/cm2. Multiply this figure by a factor of 1.2 to have a 20% safety margin, and select the nearest M grade (rounded up).
Then you can use any online calculator to calculate the concrete foundation, but it will only give an approximate consumption. It remains to be determined how much turnkey construction services will cost. Here, a lot depends on the package offers of the contractors themselves, so it is better to first contact a suitable company to clarify all the nuances. Often the price list includes the following items:
- Transportation of the crew and/or accommodation on site during construction.
- Delivery of materials and equipment.
- Rental of special equipment.
- Using a generator and delivering water if there are no communications on the site yet.
The final cost of the work may also be affected by the season, soil characteristics and the depth of the aquifers - how much it will be in ruble equivalent, the foreman will tell you after assessing the site.
Calculation of materials for strip foundation
Here it all starts with the installation of a support layer - a sand and gravel cushion. You can determine the flow rate for it using simple calculations: multiply the area of the base by the height of the compacted backfill (as a rule, it is 20-30 cm). The preliminary estimate should also include underlying waterproofing, which will prevent the solution from seeping into the pillow.
Afterwards you can proceed to the calculation of the formwork. Paired panels made of plywood or knocked down boards should have a height no less than the future strip foundation. They are installed along the external and internal perimeter of the house in accordance with the diagram. You will also need to calculate the amount of reinforcement to strengthen the concrete. It is laid in a monolithic tape with two longitudinal rods in the upper and lower parts. That is, the length of the future casting must be multiplied by 4, plus allowance for overlaps. Transverse ligaments are added to the resulting figure, which transform individual steel rods into a spatial frame. Calculators do this based on the requirements of SNiP.
At the same time, you can calculate the concrete for the strip foundation. Knowing the geometric dimensions of the base, the total volume of the mixture is determined by simply multiplying the area by the height. It is better to immediately add a reserve of about 10% so that there are no problems when the solution compacts in the mold. The possible difference between the design data and the actual volume of already assembled formwork should also be taken into account.
Then everything depends on the place where the solution is prepared. It is easier and more expensive to order its delivery from the nearest RBU - in this case, the cost of special transport services must be added to the cost of the mixture itself. It is best to confirm the final batch volume after the formwork has been assembled and re-measured on site. A more labor-intensive process is making concrete by hand. In this case, you will have to spend money on purchasing cement, sand and crushed stone, and also pay extra to the crew.
Turnkey filling price
When contacting contractors who will be pouring a strip foundation, you should decide whether you will provide them with building materials yourself or entrust the purchase to a construction company. In the first case, you only pay for the work - on average it will cost 4000-4500 rubles/m3. In the second, the cost of the finished base will be about 11,000 rubles/m3.
The concept of turnkey construction varies from company to company; the list of basic services needs to be clarified. You can find out prices for them separately if you want to save money and you are ready to do some of the work yourself. The “average” price looks like this:
- Site breakdown – 2500 rubles
- Digging trenches - 500-1000 rubles/m3.
- Sand and gravel cushion with compaction – 500-1100 rub/m3.
- Insulation tape – 150 rub/m2.
- Waterproofing is 360 rubles/m2 for single-layer pasting and 650 for two-layer.
- Assembling formwork, frame and pouring concrete - from 3000 to 4500 rubles/m3.
Approximate prices according to Moscow Region for a turnkey foundation
In the foundation calculation calculator you need to enter all the dimensions of the foundation, indicating the design features and the depth of the tape. Also, for correct calculations, you will need to independently determine the grade of concrete. Then the service will calculate everything automatically: up to the number of boards for formwork and the diameter of the reinforcement.
Online calculation service
Strip foundations are, without a doubt, the most popular among developers of all categories. There are many reasons for this: creating such a base is relatively simple, the costs of labor and materials are not the greatest. Strip foundations are successfully erected by non-professionals on their own, which persuades many to choose them. If you know the basic rules for constructing strip foundations (for example, how to create them on problematic soils), then there should be no problems with this work.
Where does the construction of a strip foundation begin?
Before you begin directly creating a strip-type foundation, you need to calculate the amount of concrete that will be needed for all work. It depends on what components will be included in the structure (for example, a waterproofing layer is not always done).
In any case, the first layer of concrete is laid on a special reinforcing layer - “concrete footing”. It consists of sand and crushed stone, which are placed in trenches to a height of 15–20 cm. After creating the concrete layer, it hardens in 5 days.
If it is decided to create a waterproofing layer, then roofing material and special compounds will be required to create it. The next stage of work on the strip foundation is laying reinforcement along and across the base. By the way, the reinforcement will also have to be calculated - only this will save the developer from unnecessary expenses and sudden shortages of material. When working with fittings, it is important to take care in advance of purchasing a reliable anti-corrosion agent for it.
When calculating the foundation, it is necessary to take into account that formwork made of boards, plywood, and slate will be used.
Calculation of concrete for strip foundations
- Total base area.
- The grade of concrete that is selected based on climatic conditions.
- Additives used (if any) – accelerating hardening, increasing frost resistance, plasticity, etc.
- Features of the use of future premises and the materials used to create them (for example, baths are heavily insulated).
It is very easy to find out the amount of concrete needed in a particular case using an online calculator. These programs use many calculation algorithms officially accepted in construction practice. Measurement data or planned dimensions of the foundation, as well as other data known to the developer, are entered into the program fields.
The ANB-group LLC company offers everyone its own online calculator, with which in a matter of seconds you can calculate the amount of concrete needed for the construction of a strip foundation. The program provides accurate and reliable data that can be fearlessly applied in practice.
When building a house yourself, it is important to get a really solid foundation, and one of the options for calculating a strip foundation is an example of a building with a perimeter of 6 × 8 m made of aerated concrete with an attic 2nd floor without basement (basement) premises. This type of support is the most universal solution in most cases of individual construction of a permanent residential building. Careful calculations at the design stage will become one of the conditions for the long-term operation of the building.
Procedure for settlement operations
The sequence of calculating a monolithic strip foundation will consist of 2 main stages, which will determine the initial data for determining the dimensions of the structure. For each specific construction site you need:
- determine the operating loads;
- find out the bearing capacity of the underlying soil.
The ratio of the effective weight load of all elements of the building, including the foundation, to the bearing capacity of the soil base will allow you to find out the optimal value of the width of the strip support.
The area of the supporting sole is of decisive importance. The width of the tape itself can vary depending on the total dimensions of the load-bearing walls (block + insulation + cladding). shown in the drawings:
For a strip structure with a rectangular cross-section, the widths along the entire vertical are equal. The choice of a T-shape, in which the area of the foundation base is larger than the base, occurs in the case of constructing a massive building (2 or more floors) from expanded clay concrete blocks or bricks. For frame houses, timber buildings, log houses, a rectangular section will usually be sufficient.
Calculations of the area of the base of the supporting part for monolithic and prefabricated types of foundation are no different.
All requirements for determining the calculated values and accepted coefficients are set out in detail in the following regulatory documents:
- SNiP 2.02.01-83*. Foundations of buildings and structures. Gosstroy USSR, 1995
- SNiP 2.03.01-84*. Concrete and reinforced concrete structures. State Construction Committee of the USSR, 1989
- SNiP 23-01-99*. Construction climatology. Gosstroy of Russia, 2003
- SNiP 2.01.07-85. Loads and impacts. State Construction Committee of the USSR, 1986
The rationality of choosing a certain type of foundation structure directly depends on the engineering and geological conditions of a given site, the working conditions in the complex of all building elements in real conditions.
Design errors, violations of foundation laying technology, and savings on work and materials not justified by calculations can lead to the need to take additional measures, the cost of which will be several times higher than the initial costs of constructing the foundation.
Load collection
The design of the foundation begins after the parameters of the building installed on it are determined.
To do this you need to do the following operations:
- draw a scale plan of the house with markings for each wall;
- set the height of the basement elevation, assign the materials used for it;
- determine the types and thickness of materials used for thermal insulation, waterproofing, wind protection, finishing of horizontal and vertical surfaces indoors and outdoors.
Find the specific gravity of each component in the reference tables. An example of such a table:
In this example of foundation calculation, you need to select:
- walls of the 1st floor made of gas block 0.4 m thick, 3 m high, 28 m perimeter - 20,160 kg;
- attic walls 1.2 m high, thickness 0.25 m, same length, log - 5150 kg;
- frame partitions, 17 m long and 2.7 m high, 16 m – 1.2 m, weighing 19530 kg in total;
- plank flooring on wooden beams with an insulation density of 200 kg/m³ - 14400 kg (floors of the 1st and 2nd floors), with a coefficient of 1.2 = 17280 kg;
- gable roof made of ondulin with an area of 58 m² - 1740 kg, with coefficient. 1.1 = 1914 kg;
- payload is 200 kg/m², (safety factor 1.2) – 11520 kg.
In total, the weight of the main above-ground structures will be 75554 kg.
If a private house does not have a small base area at a significant height, then the influence of wind load on the foundation can be neglected.
It is better to take the snow load according to the maximum value for a given zone (100 kg/m²). With a safety factor of 1.4, the roof would weigh 8,120 kg.
In total, the estimated weight of the house without foundation will be 83,674 kg
For small private buildings, the division of loads is usually neglected and simply summed up without using combination reduction factors in the calculation.
Foundation height
When assigning a design task, it is necessary to determine the dimensions of the strip base. To determine the load from the foundation, you need to set its depth.
Seasonal indicators are shown on the maps:
For a more detailed calculation, this value is taken from the table:
The regulatory requirement for the location of the bottom of the buried foundation is 0.2-0.3 m below the freezing mark in a given climatic zone.
- below the freezing depth for clay and loam the mark is taken equal to 0.5 GP; for other types of soil there is no dependence;
- above GP - not lower than GP (except for gravelly, rocky sands).
For light buildings (wooden, foam concrete, small brick) on slightly heaving soils, it will be 0.5 - 0.7 m. In the design calculations, a coefficient of 1.1 is used. Accordingly, for the house being built in the example, you should choose a depth of 0.6 m and a base height of 0.4 m.
Tape weight
You need to add the own weight of the support to the calculated load of the house. You can build from foundation blocks and take the values from the table:
When laying FBS 24.4.6 in 1 row to ground level, the weight without adding brick to the base will be 15,167 kg. A base made of solid brick 0.4 × 0.4 m will weigh 8064 kg. The total weight of such a foundation will be 23231 kg with a support area of 0.4 m × 28 m = 11.2 m². Now you should calculate a light self-leveling foundation with a widened base.
The height of the underground part of the monolithic concrete strip will be 0.6 m, the base 0.4 m, the thickness is equal to the wall made of blocks 0.4 m. Non-reinforced concrete has a volumetric weight of 2400 kg/m³, load safety factor = 1.1. Then the load will be: 1 m × 0.4 m × 2400 kg/m³ × 1.1 = 1056 kg/m.
The width of the foundation base should be taken as 0.6 m. If we subtract from it the previously taken into account tape size of 0.4 m, we can obtain a total protrusion of 0.2 m.
The weight of the reinforced concrete base at 0.3 m is 2500 kg/m³, in our case it will be 0.3 m × 0.6 m × 2500 kg/m³ × 1.1 = 495 kg/m.
Backfill soil with a density of 1650 kg/m³, coefficient 1.15. The result is 0.2m × 1650kg/m³ × 0.3m × 1.15 = 113.85 kg/m.
We add up the resulting load values 1664.85 kg/m or 46615.8 kg. The sole area for this option is 0.6 m × 28 m = 16.8 m²
We perform a similar calculation for a rectangular concrete monolith 0.3 m wide (with a recessed base): 1 m × 0.3 m × 2400 kg/m³ × 1.1 = 792 kg/m. The mass of the entire belt will be 22176 kg, the support area will be 8.4 m².
Base load-bearing capacity
To accurately calculate the bearing capacity of the soil lying on a site, its physical and mechanical characteristics obtained as a result of engineering and geological surveys will be required. The costs of ordering an IGE report in the future can pay off handsomely if the site is located in difficult unfavorable conditions.
In a simplified way, you can use reference tables that contain the given values of this indicator for typical types of soil, for example, the following table:
An important condition is the homogeneity of the underlying layer without the formation of so-called “lenses”. To clarify all the features, practical research into the geology of the site and desk calculations are needed based on the most accurate data.
Carrier Ratio
It is possible to create the selected foundation option if the total load from the building is less (in extreme cases, equal) to the bearing capacity of the soil. We consider the resulting strip base options:
- FBS 24.4.6 blocks with a brick base (83674 kg + 23231 kg)/11.2 m² = 9545 kg/m² or 1 kg/cm².
- Monolithic concrete with an expanded base (83674 kg + 46615.8 kg)/16.8 m² = 7754 kg/m² or 0.8 kg/cm².
- A strip monolith 0.3 m wide will have the following value: (83674 kg + 22176 kg)/8.4 m² = 12601 kg/m² or 1.3 kg/cm².
From the comparison it is clear that at minimal cost it is possible to build a building weighing 106 tons on a self-leveling strip foundation 0.3 m wide.
Expert advice on how to independently calculate the supporting area of foundations when building your own house is presented in this video:
Advanced builders can always use free calculation programs that can be downloaded (or worked online) on the Internet.
An example of such a program is shown in the photo:
However, there are doubts about the accuracy of calculations of complex cases on these calculators, since the operation of their formulas is not clearly controlled by the user (applied rounding and completeness of the calculation).
A reliable result is obtained using the methods given in building codes and special reference literature. It is advisable to use calculator programs to more easily calculate the required amount of consumables.