The foundation is the underground part of a building or structure that receives loads and transfers them to the ground. The most popular type of foundation for building houses is considered to be a strip foundation. This widespread use of strip foundations is explained by its versatility and affordable cost. Before you begin construction, you need to make a choice between a shallow and buried strip foundation.
A shallow foundation saves both budget and time. And labor costs will be significantly less, since its construction does not require a deep pit. The following foundation is used for lightweight structures of small area:
The depth of the shallow foundation reaches half a meter.
This foundation is used for the construction of structures with heavy walls, concrete floors, a basement or an underground garage. The length of the foundation depth must be calculated in advance. First, you need to determine the level of soil freezing, then subtract 30 cm and lay the foundation at this depth.
To build a strip foundation yourself, you must first carry out precise planning. The need for careful calculations is explained by the fact that the foundation is one of the most important structural elements of any building or home. Mistakes made at the beginning of construction can provoke negative consequences during the operation of the house.
Marking is carried out by marking on the ground both the external and internal boundaries of the future foundation. To do this, it is best to use pegs or reinforcement rods and ropes. But it will be more effective to use special devices, such as laser levels. Remember that large errors in markings will noticeably affect the appearance of the finished building.
To achieve ideal results you need:
When you are finished with the markings, study the differences in the surface at the construction site and select the lowest point to measure the depth of the trench and eliminate the difference in the height of the foundation. If the building is planned to be small, then the depth of the pit can be 40 cm.
A sand cushion with added gravel should be laid on the finished trench. The recommended height of each layer is 120-150 mm. After this, each layer must be shed with water and compacted to increase density. To insulate the finished pillow, you need to lay out a durable waterproofing film on it.
The formwork is usually made of planed boards approximately 40-50 mm thick. You can use slate for this purpose.
When erecting formwork, control verticality. The recommended height of the frame above the ground is 30 cm. This is necessary to build a small base. Asbestos concrete pipes are laid in the formwork to introduce sewerage and water supply into the building.
Place a plastic film between the concrete and the formwork; this will protect the formwork from contamination.
The next stage is the installation of fittings. Reinforcing bars with a cross-section of 10-12 mm are connected with a special knitting wire so that the sides of the square cells are 30-40 cm. The reinforcement can be either steel or fiberglass.
Fill the formwork with concrete gradually. The thickness of the layers is 15-20 cm; to avoid voids and increase overall strength, compact the layers with a special tool - a wooden tamper or an internal vibrator.
You can order ready-mixed concrete from a factory or make it yourself using a concrete mixer. The recommended proportion of cement, sand and crushed stone is: 1:3:5.
The layers should not differ in composition. In cold weather, you should use a concrete heater and frost-resistant additives; in hot weather, water the concrete.
Once the concrete is poured, it should be covered with film to prevent drying out and left to gain strength for at least 2 weeks.
The online strip foundation calculator will be useful for both developers who install it themselves and professional builders. The service allows you to determine the area of the base of the foundation strip, which can subsequently be used to calculate waterproofing, as well as the volume of concrete, reinforcement, wire for tying it, and material for formwork.
The importance of accurately calculating the strip foundation will allow you to avoid cost overruns, which amount to a quarter of the cost on the scale of the entire construction. Compliance with the construction schedule can be disrupted by forced downtime when it turns out that due to a simple error in manual calculations there is not enough material.
The calculation of a strip foundation for a house is based on the use of the following design parameters:
These parameters are quite sufficient for calculating concrete. The cubic capacity of the base (its volume) calculated by the concrete calculator for a strip foundation will represent the consumption of concrete for the construction of the entire structure.
The selection of the components of a concrete mixture (water, cement, crushed stone, sand) depends on the brand of concrete, the mobility indicator of the mixture, the brand of cement, the fraction of fine and coarse aggregate, and the type of superplasticizer. By entering the weight of the finished concrete mixture in one bag into the field of the online calculator, you can obtain the concrete consumption for constructing a unit volume of a strip foundation.
To calculate the reinforcement for a strip foundation, you must fill in the following fields in the calculator:
The construction calculator for determining the material consumption for strip foundation formwork will perform all the calculations so that the temporary enclosing structure can withstand the enormous pressure of the concrete mixture. The initial data for the calculations are:
As a result, the calculator will display the volume of lumber required, the recommended number of supports and the spacing between them.
An important function of the service is to determine the cost of a strip foundation, determined taking into account the price per bag of cement, per ton of sand, crushed stone, reinforcement, per cubic meter of boards and their calculated quantity in the corresponding units of measurement.
The method for determining the required materials using an example will help you understand the algorithm for calculating their consumption using a calculator.
For example, the project provides for the construction of a house with plan dimensions of 9 x 7 meters. The internal walls are 22 meters long. As a result, the total length of the foundation will be:
2 (9 + 7) + 22 =54 meters.
The initial data for the calculation are:
All parameters must be reduced to one unit of measurement.
A project is needed when building any house. It does not have to be professional, that is, carried out by a specialist from a construction or design organization. These calculations can be performed independently, at least in order to accurately represent the amount of concrete in cubic meters required to pour the foundation. After all, this is the most important calculation, the correctness of which will allow you to avoid, for example, overuse of building materials, and therefore save money.
The initial data that will be required to determine the amount of concrete required to pour the foundation will be as follows:
A strip foundation is an inextricable rigid structure laid under each load-bearing wall of a building and forming a closed loop. The method for calculating this type of foundation is associated with these features.
Basic formulas for calculating the volume of concrete for a foundation
To calculate the amount of concrete you will need the following data:
The width of the foundation strip is determined based on the support area of the foundation. Typically this value is 20-40 cm. The height of the tape is determined by the height of the above-ground part of the foundation, which is usually no more than 50 cm, as well as its depth, which can reach several meters.
This value is determined based on several factors, for example, how deep the groundwater runs under the building under construction, as well as the depth of soil freezing. For example, in sandy soil and in water-saturated soils, a laying depth of 2.5 m is considered the most justified. For small country houses, under normal conditions in the middle zone, one and a half meters is enough. Accordingly, to determine the height of the strip of such a foundation, it will be necessary to add 40 cm of the above-ground part to the 1500 cm depth of the foundation.
The total length of the tape will be entirely determined by the configuration of the foundation. In most cases, calculating the total length is not difficult - you need to add the internal load-bearing walls to the total length of the external walls. And we get the volume of concrete by simply multiplying the length of the foundation by its height and width:
Vb = lhs, where l, h and s are the length, height and width of the foundation, respectively.
It should be borne in mind that the amount of concrete calculated using this formula does not take into account the inevitable losses during transportation, pouring, compaction of the mixture, its leakage through gaps, as well as absorption into the wooden elements of the formwork. On the other hand, the design also contains metal reinforcement, which, by reducing the useful volume, somewhat compensates for losses.
However, in practice the latter are still much more significant, so the result obtained from the formula presented above needs to be corrected:
That is, the final formula for calculating the amount of concrete for a strip foundation will take the following form: V = Vb + 0.02Vb
A slab foundation is an ordinary monolithic reinforced concrete slab at the base of a building. Accordingly, to calculate the volume of concrete required to pour a given type of foundation, you simply need to multiply its length, width and height. The minimum height for this type of foundation is 10 cm. In accordance with this, we can give approximate data on the consumption of concrete for a building with sides, for example, 8 x 8 m:
However, this type of construction also has some of its own characteristics, which directly affect the consumption of concrete. So that the slab is stiffer and more resistant to deformation, stiffening ribs are made along its edges, as well as in the longitudinal and transverse directions in increments of approximately 3 meters, dividing the foundation into squares.
They are usually performed on the lower surface due, firstly, to a simpler pouring technology, and secondly, this way the upper part of the slab remains smooth. Accordingly, these stiffeners will also require concrete in an amount that can be calculated knowing their cross-sectional area and total length.
The ribs can be either rectangular or trapezoidal. The height of these structural elements of a slab foundation is usually taken equal to the thickness of the latter, and the width is approximately 80% of the height. Thus, the formula for calculating the amount of concrete for a slab foundation with rectangular stiffeners is quite simple:
Vb = lhs + lр*sр*h, where the following values:
If the latter are planned to be made with a cross-section in the form of a trapezoid rather than a rectangle, then calculating the volume of concrete mixture required to fill these ribs will be reduced to multiplying the cross-sectional area of this trapezoid by the total length of the ribs.
Trapezoidal ribs have their own peculiarity - usually the ratio of the lengths of their bases is 1.5, that is, the larger base of the rib will be approximately one and a half times longer than its height, and the smaller one will be equal to the height or even be slightly shorter - up to 80% of its value.
Let us recall the formula for calculating the area of a trapezoid:
S = h(a+b)/2, where a and b are the bases, h is the height of the trapezoid.
Thus, the formula for calculating the volume of a slab foundation with trapezoidal stiffeners will look like:
Vb = lhs + lр*h(0.8h+1.5h)/2
Even from the name it is clear that a columnar foundation is a set of concrete piles dug into the ground. They are, as a rule, located at the intersections of the walls of the house, but if necessary, they are also dug into the spans. The head is the upper part of the pile, usually located at a height of 40-50 cm, but the full height is also determined by its lower part - the base.
One of the advantages of a columnar foundation is its efficiency, that is, the consumption of concrete poured onto it is minimal. Calculating the amount of concrete should also not cause much difficulty. For round columns, when making calculations, you need to know the following initial data:
It is not difficult to guess that the volume of one such column will be equal to the height multiplied by the cross-sectional area of the pile. The latter is equal to the square of the radius multiplied by 3.14. Accordingly, the volume of concrete will be calculated using the formula:
V = 3.14R 2 nh, where R, n and h are the radius, number of piles and their height, respectively.
If square columns are used, then the calculation becomes even simpler:
V = a*h*n, where a is the length of the side of the pile.
When building a house, one of the important components of competent organization of the entire process is the correct calculation of the amount of materials used. Of course, all stages of construction are important, but one of the first to be calculated is the foundation, namely the amount of materials that will need to be spent when pouring it. At the same time, if accurate calculations are obtained in specialized programs or manually, then approximate figures will be given by an online calculation of the strip foundation of a house - if its geometry is not too complex, then this data will be quite sufficient.
One of the interface options for the online foundation calculator
To find out the approximate cost of a strip foundation, use the following calculator:
You must understand that any automatic calculation of the foundation online calculator can produce with a certain error. Its value depends at least on whether a simple formula is used to calculate the volume, or whether it additionally takes into account the correction factors derived to calculate the amount of concrete. Additionally, the difference in the geometry of a standard rectangular foundation or one designed for additional load-bearing walls inside the perimeter must be taken into account.
As a result, the websites post either a free calculator for the cost of the foundation as a whole, or programs that calculate its individual parameters - the volume of concrete, the amount of reinforcement, as well as the boards that are needed to create the formwork. Along with the boards, you must not forget to count the beams for the spacers and the nails with which it will all be fastened.
You also need to remember that online calculations will never give a 100% guarantee of the correctness of the result, because on the website you need to enter the required data and the program will simply display the final result of the calculations without any explanation. So that you don’t have to take them all on faith, you need to understand with the help of what formulas and data you can double-check the result of online calculations.
An example of using an online calculator in the video:
When using online calculators, it is assumed that all loads have already been calculated for the foundation. This means that it is calculated how many bricks will go on the walls and how much weight will put pressure on the base. You also need to take into account the impact of wind loads and the weight of snow that will lie on the roof in winter. Simply put, all the calculations have already been made, the user has decided on the linear dimensions and now you just need to calculate the amount of concrete that will be poured.
Here it is necessary to take into account a number of nuances, ignoring which will lead to ordering insufficient or excessive quantities of concrete:
At first glance, calculating a strip foundation is simple - take the length, width and depth, multiply everything and get the volume. The nuance here is that this method works ideally for a straight line, but since the foundation is at least rectangular, serious errors creep into the calculations.
For example, the simplest case is a 6x8 foundation with a perimeter (6x8)*2=28 m, without internal load-bearing walls, a width of 0.4 m and a height of 1.7 m - if you simply multiply all these values, you get 19.04 m³ . With these calculations, if the formwork is done correctly, concrete will remain in the machine after pouring. This will happen because when the concrete for the foundation was calculated, the calculator did not take into account the difference between the outer and inner perimeters of the foundation.
If you calculate each wall separately and mark for yourself the already “counted” places, then the picture will be as follows:
The larger foundation walls are calculated separately. Length 8 multiplied by width 0.4 and height 1.7 - the result is 5.44. Since there are two walls, the result doubles: 5.44*2=10.88 m³.
Now it's the turn of the smaller walls. If you mark on the plan the larger walls that have already been calculated, it becomes clear that not all 6 meters of length need to be taken into account, because 40 cm on each side are already “occupied”. With correct calculations, 6-0.4-0.4 = 5.2 m is taken. This value is multiplied by the width and height and the result is 5.2 * 0.4 * 1.7 = 3.536 m³. For two walls it will be 3.536*2=7.072.
As a result, instead of the initially calculated 19.04, it will take 17.95 m³ for all the foundation walls, and an extra cube of concrete costs several thousand rubles due to a seemingly childish and obvious mistake.
The reasons for the incorrect calculation are clearly shown in the video:
Of course, with complex shapes, a standard concrete foundation calculator is unlikely to be able to calculate all the nuances. This means that you will have to calculate everything manually for each element separately, noting for yourself which volume has already been taken into account and which has not yet been taken into account. In addition, experts take into account the space that will not be occupied by concrete - these are fittings and ventilation holes, which in total also occupy a noticeable volume.
Whether it is worth considering a reserve and how much concrete to provide for it depends entirely on the professionalism of those who will install the formwork. If there is an error of even 1 cm in the width of the foundation, this will seriously affect the volume. For example, with the same values, but the width of the foundation is 1 cm larger, the result is (8 + 8 + 5.2 + 5.2) * 1.7 * 0.41 = 18.4 m³ - an extra half cube of concrete.
As a result, everything depends on the correct fastening of the formwork, the strength of the bars holding it and the conscientiousness of the builders, but in any case it is advisable to order 5-10% more concrete and, in case it still remains, provide a place where it can be used.
Excess concrete can be poured into a concrete mixer Source allarenda24.ru
When professionally calculating reinforcement for a foundation, it is necessary to take into account a large number of factors that influence the choice of the cross-section of the rods and their number. This takes into account the type of soil, depth, and the presence or absence of an additional base. The number of nuances is quite large, so it is clear that the calculator can only approximately calculate the reinforcement for a strip foundation. Approximately the following algorithm is used:
In the case of low-rise construction, four load-bearing rods are most often laid in the foundation frame - in the section of the strip they are located in the corners. Accordingly, to get their total length, you need to multiply the length of all foundation walls (perimeter and, if any, internal ones) by four. In our example, the perimeter is (6+8)*2=28, multiplying it by 4 - we get 112 meters of the total length of the rods. The quantity must be taken in reserve, since the rods will most likely be laid overlapping (overlap length 50 cm). The number of overlaps must be calculated based on the length of the reinforcement bars that will be purchased. If it is 12 meters, then 28:12 = 2.3 - this means that there will be 3 overlaps on each rod. If it’s 6 meters, then 28:6=4.66 – there will be 5 overlaps.
It should also be taken into account that the number of strips and rods in each of them will be different, depending on the type of foundation, the soil on which it is laid, etc. Not a single online foundation calculator can predict their exact number, since there are too many variables to take into account.
An example of the location of reinforcement in a foundation strip Source stroim-dom.radiomoon.ru
If you look at the foundation strip in cross-section, the lintels are located 5 centimeters from the edge of the concrete pour. With a tape width of 40 cm and a height of 170, jumpers with a length of 30 and 160 cm will be needed, respectively.
The jumpers are located at a distance of 0.5 meters from each other. With a perimeter of 28 meters, their number will be 28*0.5=56. Each lintel has two pairs of rods, one 30 cm long, and the second 160 cm long. just one lintel will cost (30*2)+(160*2)=3.8 meters of reinforcement and this length must be multiplied by the number of lintels. As a result, lintels will require 3.8*56=212.8 meters of reinforcement. Based on the length of the purchased reinforcement, the online reinforcement calculator will help you calculate the number of scraps, and, accordingly, how many rods you need to purchase, but again with a certain error.
Experts do not recommend welding pieces of reinforcement together, since this disrupts the molecular structure of the metal - it becomes brittle and does not resist deformation well. The best option, which should take into account the calculation of the cost of the foundation, remains twisting the rods together at the points of contact with burnt metal wire. It is also better not to use the usual one - it has low tensile strength.
Tying jumpers and rods with wire Source readmehouse.ru
In our example there are a total of 56 jumpers, each of which has 4 touch points. In total, you will need to make twists on 56*4=224 connections. Depending on the thickness of the reinforcement, each twist will require 0.3-0.5 m of wire, and this is a coil 67.2-112 meters long.
Here you just need to calculate the area of all the foundation walls. From the first example it is clear that using only the outer perimeter is partly the wrong solution. This means that we need to make a calculation for two perimeters - external and internal. In the first case it is (6+8)*2=28, and in the second all the walls will be 80 cm shorter - which means we get (5.2+7.2)*2=24.8. The total perimeter of the foundation walls will be 28 + 24.8 = 52.8 meters. To get the area, we multiply this number by the height of the walls, we get 52.8 * 1.7 = 89.76 m².
To find out the required number of boards, calculate the area of one of them. For example, boards 6 meters long, 20 cm wide and 2.5 cm thick are purchased. The area of each of them in this case will be 6*0.2=1.2 m², and the volume 1.2*0.025=0.03 m³ .
Formwork for strip foundations made of boards Source ravchan.ru
Accordingly, the number of boards purchased will be 89.76: 1.2 = 74.8 (rounded to 75), and if the order is made in cubic meters, then 75 * 0.03≈2.25 m³.
Of course, it is better to purchase with a reserve, because any calculations must take into account the error - in this case it will be scraps, the amount of which depends on the length of the boards and the perimeter of the foundation walls.
If the formwork is installed correctly, after disassembling it, the boards are quite suitable for further use. Of course, they are unlikely to be used in final finishing, but for subfloors or scaffolding they will come in very handy - this point should not be discounted during initial calculations, especially if there is a latent desire to save on formwork.
Typically, online foundation calculators do not add such functionality, since there are enough of these materials on the construction site. But at the same time, you should not forget about them if the construction will be carried out in a new place where tools and consumables have not yet been delivered. If you want to save on supports, you can evaluate the possibility of using different options for supports - install independent ones, on each wall separately, or use a circular scheme.
Examples of formwork supports for strip foundations Source stroim-dom.radiomoon.ru
On our website you can find a list of companies providing services for construction of the foundations of country houses, and the Low-Rise Country houses presented at the exhibition.
From the examples given, it is clear that calculating the amount of material that will be required for the foundation is a fairly simple task. If its form is simple, then the foundation calculator will calculate the cement without any inaccuracies and will also give recommendations on how much to purchase other materials - reinforcement and boards.
Another question is if the foundation has a complex shape or will be installed on specific soils. In this case, it is better to trust specialists who will perform calculations in accordance with all standards and requirements, and use online counting machines only for approximate calculation of the amount of materials.
Construction technologies have been developing over many centuries.
One of the most important elements of any building is the foundation, which ensures the integrity and durability of the entire house.
The main and most successful version of the base design is a simple and reliable type of support system.
With the advent of high-quality and affordable concrete, the tape has gained capabilities that are far superior to the properties of alternative options, primarily in terms of load-bearing capacity and efficiency.
At the same time, the performance of the tape is almost completely determined by the quality of the material, its composition and properties.
Class and grade are two independent quantities indicating the quality of concrete.
Both of them reflect the degree of compressive strength of the material, but differ in specialization.
Grade (M) - an indicator related to the quantitative value of cement content. Class (B) - an indicator of the material’s resistance to external loads.
The grade of concrete demonstrates the cement content. This is a very unstable and uninformative indicator, the main value of which is the freezing time.
Two pieces of hardened concrete with different qualities can have the same grade, since the cement content does not completely determine the finishing quality of the material. There are brands from M50 to M500.
The most common of them is M200, which is used for, production of stairs and other structural elements.
Smaller grades are used to fill the preparatory layer of the strip foundation or auxiliary elements.
More durable grades - M300-M500 are used for casting special structures, dams, and critical reinforced concrete parts.
Unlike the grade, which shows the average strength value and allows significant fluctuations in quality, the concrete class indicates the ultimate strength, which is ensured in 95% of cases.
The class is a more accurate indicator, so most manufacturers switch to class when designating the quality of a material, although the use of the brand by inertia is also widespread.
The volume of concrete is calculated based on the design parameters of the tape. In order to determine the required amount of material, it is necessary to calculate the volume of the tape.
The cross-sectional area is determined by multiplying the width by the height. Then the resulting value is multiplied by the total length of the strip foundation, taking into account the length of all sections, including lintels.
It is necessary to use the same units of measurement to avoid confusion in determining the digits.
If the length of the tape is in meters, then the cross-section must be calculated in square meters.
IMPORTANT!
Some sellers list their goods in tons, while others count their goods in cubic meters. The volume of concrete obtained in the calculation may need to be converted into weight units, for which it is necessary to know the specific gravity of the concrete of the desired grade. This table value is available in the SNiP appendices. The volume is multiplied by the specific gravity to obtain the total amount of material.
Let's consider a specific example of calculation. There is a tape with a total length of 30 m, a width of 40 cm and a height of 1 m.
Determining the cross section:
0.4 1 = 0.4 m2.
Tape volume:
0.4 30 = 12 m3.
Weight of concrete (grade M200):
2.432 12 = 29.184 tons.
NOTE!
All values must be increased by 10-15% in order to have some reserve just in case. Therefore, it is necessary to prepare the material at the rate of 32 tons (we increase 29.2 by about 10%).
Basic requirements for concrete used in the manufacture of critical load-bearing structures:
The numerical values of the required parameters are determined by the purpose of the tape, magnitude of loads and operating conditions.
Self-production requires experience, the use of equipment and several assistants, otherwise there is a risk of interrupting the pouring of the foundation, which is unacceptable.
If for some reason it is not possible to order ready-made concrete, you have to prepare it yourself. To do this, you need to know what components are used in the manufacture of the material and in what quantities they are present in the mixture.
Common types of concrete consist of the following elements:
IMPORTANT!
Do not confuse concrete for pouring the foundation and mortar for laying bricks. These are different materials. No additives for elasticity (soap solutions or lime) should be added. The material should be as rigid as possible.
The most common proportion for making structural types of concrete:
Depending on the specialization and characteristics of the foundation, these proportions may change in one direction or another.
The cement usually used for the production of heavy concrete belongs to the M400 or M500 grades. Smaller species are not suitable for such purposes.
The sand must be clean and free of foreign impurities. Used river, less often - washed gully, without foreign impurities.
Organic matter and clay inclusions are especially undesirable. They increase the creep and shrinkage of the material, so they need to be gotten rid of.
The crushed stone used in preparing the mixture must be of medium size (1-3 cm) and free of organic impurities.
The presence of aggregates (sand and crushed stone) in concrete is mandatory. Water and cement form the so-called. concrete stone, highly susceptible to shrinkage, reaching up to 2 mm per meter of height.
The presence of fillers reduces shrinkage and forms a kind of, receiving loads and redistributing them throughout the entire volume of the material.
When talking about the proportions of concrete, we should focus on the units of measurement. Usually parts are counted in weight units.
In practice, they most often use volumetric measures, for example, buckets.
It must be borne in mind that the weight of one bucket is different for each material:
Taking into account the difference in volumetric weight, the optimal proportion of components (in buckets) will be the ratio 2-5-9 (C-P-SC).
Water is usually added to half the volume of cement. Knowledge of these subtleties will allow you to correctly mix the composition and avoid mistakes when creating such a critical structure as a strip foundation.
The best way to make concrete is to use a concrete mixer. It is not necessary to purchase it for your own use; you can rent the device for several days.
It is necessary to mix such an amount of material that can be used in 2 hours.
This rule allows material to be supplied rhythmically to the site without overloading workers..
It should be noted that the most important thing is to do the work as quickly as possible, so you should be guided by the requirements of the situation.
Concrete is mixed as follows::
If wet sand is used, the amount of water should be reduced slightly. In general, the consistency of the material is determined by your own feelings.
If necessary, add water, since the concrete is poured into it. Material that is too thick does not lay down evenly and forms bubbles that are difficult to get rid of.
In this section you will find out how much concrete is needed for a strip foundation:
The quality of concrete directly depends on the properties of the components, proportions and manufacturing technology.
When making it yourself, it is possible to control the composition of the mixture, but when using ready-made concrete, larger quality tolerances should be taken into account and a heavier grade should be chosen.
This will not make a big difference in costs, but will help to obtain a high-quality and durable material for filling the tape.
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