# How to calculate the reinforcement on the foundation

3.14×200 = 628 mm.

On one pile you need 3 strapping:

3×628 = 1884 mm (rounded 1.9 m).

The total length of the connecting elements at 16 points:

Foundation installation diagram.

The calculation of the longitudinal reinforcement for the grillage is similar to the calculation for the strip footing. In total, 152.4 m is needed. But the transverse rod, taking into account the height of the grillage of 400 mm, will be required somewhat less. The total length of four profiles for one bundle will be:

4x (400-2×50) = 1200 mm = 1.2 m.

At 119 connections you need:

For piles with a cross-sectional diameter of less than 200, you can take 3 rods. Increasing this size increases the amount of reinforcement required.

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## Calculation for monolithic base

Monolithic reinforced concrete slab is placed under the entire area of the building.

Among all types of foundations, slab most financially costly, this applies to both concrete and reinforcement.

Laying monolithic base is justified on soft and mobile soils.

The scheme of reinforcement of the monolithic base plate.

It provides maximum stability and is best opposed to heaving forces. In case of any ground movement, the entire slab is lowered or raised, preventing distortions and cracking of walls. Because of this, the monolithic base was called floating.

We will calculate the reinforcement for the slab foundation for a building of 10×6 m. The thickness of the slab is determined by calculating the load on the foundation. In our example, it will be 30 cm. Reinforcement is performed by two belts with a grid step of 20 cm. It is easy to calculate what you need for each belt:

1000/200 = 50 transverse rods with a length of 6 m,

6000/200 = 30 longitudinal bars 8 m long

The total length of 2 belts will be:

(50×6 + 30×8) x2 = 1200 m.

The connection of the belts is made by reinforcement of a smooth profile. Total number:

50 x 30 = 1500 knots.

Taking into account the distance from the edges of the slab 5 cm each, the length of the connecting rod is 0.2 m. Thus, a smooth profile is necessary:

In addition, it will be necessary to take care of the acquisition of wire for the bundle. The required amount is determined at the rate of 30 cm per node. In our case:

## Armature for the foundation. Calculation of reinforcement for slab foundation

Reinforcement technology helps to achieve optimal building strength in modern construction. The ways of its implementation are diverse and the choice of a concrete one depends on a number of parameters of the object being strengthened. The most widespread reinforcement received as an element of the foundation – thanks to the metal rods formed high-strength building component called reinforced concrete. In this case, the integration of the rods into the concrete base must be strictly calculated, otherwise all efforts to create a reliable platform will be in vain.

## Parameters for calculating reinforcement

The calculation of the volume and parameters of the metal “skeleton” is impossible without knowledge of the required properties relative to the building itself. Based on its characteristics, fittings for the foundation are selected. The calculation is made on several indicators that determine the technical and operational quality of the structure.

The list of basic values includes the following parameters:

- the mass of rods used;
- the length of each element;
- total weight of the frame;
- diameter and ribbing;
- number of rods.

It would seem that the use of the maximum possible amount of reinforcement will allow to achieve the highest technical and operational qualities of the foundation of the building. But this is not the case, since improper distribution of the loads on the foundation can lead to the opposite effect, weakening the structure.

## Calculation for slab foundation

One of the popular types of foundation is slab. In this case, ribbed rods with a diameter of at least 1 cm are used. The choice of thickness depends on the planned mass of the house and the characteristics of the soil. For example, if a wooden structure is being built, then the calculation of reinforcement for a slab foundation may assume the minimum allowable thickness. In the case of a stone or brick house, this figure averages 1.5 cm. Based on these data, the optimal amount of reinforcing material is selected.

## Reinforcement mesh spacing

The number of rods, as well as their size, must be calculated by the grid step. So, if reinforcement on a slab foundation of 6×6 m is planned, then the gap will be 20 cm. That is, you will need to install 31 rods along and across. Accordingly, the calculation of the number of reinforcement for the foundation in this case shows the need to use 62 rods. But this is not all yet – since two belts form at the plate, the primary result is multiplied by two – in the end, 124 units are obtained. The total length of the material, provided that one rod has a length of 6 m, will be 744 m.

Also required and fittings. It is calculated individually and on the basis of the width of the belt – these are interlocking rods of several decimeters in length. In the case of the described foundation, the total length of the auxiliary reinforcement will be about 100 m.

## Calculation for strip footing

In the construction of the tape base for the home, fittings with a diameter of 10-14 mm are also used. But there is one difference that determines the specificity of the consumption of rods in such foundations. The fact is that the concrete structure of the tape type is more resistant to bending, so the thickness will initially be understated when compared with the slab counterpart.

For longitudinal reinforcement, A3 rods are used. Their function is to receive a direct load on the foundation, which determines the need to use twigs with a ribbed surface. Less high loads fall on the vertical and transverse elements, so they can be smooth – grade A1. Usually, the calculation of reinforcement for strip foundations involves the installation of four rods in the longitudinal direction – two for each belt. If the requirements for reliability increase due to the instability of the soil or the characteristics of the building itself, it is possible to increase the number of rods.

## Calculation for a column base

This type of foundation involves the use of reinforcing rods with the smallest thickness — a diameter of 1-1.2 cm is common. Ribbed vertical rods A3 take the main load, while elements of the horizontal direction (0.6 cm thick) perform only the function of a bundle.

As an illustration of the reinforcement, you can take a column 2 m long and 40 cm in diameter. Here you will need four elements with a diameter of 1.2 cm, between which a pitch of 20 cm is maintained. Smooth rods with a diameter of 6 mm will perform their fastening. Regarding the length, the calculation of the reinforcement of the column foundation can be represented as follows: four vertical bars of 2 m in total will be 8 m.

## Reinforcement schemes

The shape of the metal frame in the concrete base depends on the chosen reinforcement scheme. The latter, in turn, will determine the effectiveness of the configuration used – in each case it may be different.

The main rule in the choice of the scheme of forming the structure of metal rods is a bias towards the correct forms. Installation of reinforcement elements in the form of a rectangle or square, as practice shows, provides the highest reliability of the building. However, other decisions on the device of the reinforcing frame are not excluded if the project of the house itself deviates from the standards.

The layout of the rods in the concrete structure must take into account additional reinforcement, which, however, is not so necessary if the foundation is constructed. The calculation of reinforcement with reinforcement is usually used in tape reinforced concrete bookmarks when corners and joints are formed.

## Fitting fixture

Even the correct calculation of reinforcement will not ensure the reliability and durability of the foundation, if an unsuccessful method of fixing the rods is chosen. Usually, welding is used to connect metal structures and parts, but in the case of reinforcement, it is desirable to stop at the wire fastening – the material structure will retain its original qualities, having reliably strengthened the concrete.

For this, knitting wire and a special hook are used to create knots. Optimum strength of the frame is possible only with a uniform connection of the areas of convergence of the rods – exceptions concern the corner sections that require reinforcement. Additionally reinforced reinforcement for the foundation, the calculation of which takes into account the “problem” places of the joints and turns, will ensure the protection of the structure from physical impacts.

On average, about 25 cm of knitting wire is spent on each joint. It is possible to increase the reliability of the nodal connection by double strapping, after which the crochet hook can be used.

## Reinforcement errors

The best way to insure against incorrect selection and installation of reinforcement is to strictly follow the project documentation. Ignoring the established construction parameters can be associated with the desire to save, the lack of the necessary material, etc. Each of these cases creates a security risk for the facility being constructed. It is also not recommended to forget about the technological rules by which reinforcement for the foundation is selected. Calculating it will optimize further installation, but the main contribution to the success of the project will make the primary quality of the material.

In addition, the following errors should be prevented in the organization and in the reinforcement itself:

- Application of non-compliant reinforcement. Smooth rods will not be able to replace analogues with a ribbed surface, as well as one category of material – another.
- Unprepared metal surface. The presence of fat, corrosion and dirt is unacceptable, because it reduces the adhesive qualities of the material.
- Errors in the calculation of the intervals in accordance with which the reinforcement for the foundation is laid. The calculation of the pitch from one rod to the other should not be less than 2 cm – this is unjustified from the point of view of structural reliability and proportional load distribution.
- Connection of reinforcement in places of stretching the concrete base. If there is a shortage of reinforcement length, a lining method is used. Although there are cases when such a technique is allowed, it is desirable to avoid unnecessary bonding points.

## Features of the calculation of fiberglass reinforcement

Advantages of the composite analogue of metal rods determined its popularity. In terms of diameter and mass, the calculation of fiberglass reinforcement for the foundation is somewhat different. First, an innovative material is several times lighter than steel – so, the weight of a 100-meter reinforcement wrap of fiberglass is 8 kg. Secondly, the composite increases the strength properties of concrete, which allows reducing the thickness of reinforcement elements. For example, if metal bars with a diameter of 1 cm are declared in the project, then it can be limited to 0.8 cm. Diameter.

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## How to calculate the amount of reinforcement for a tape base?

The foundation of any building is the arrangement of the foundation. The correct calculation and bookmark will be direct prerequisites for the strength and durability of the structure. To carry various loads, including deformation, reinforcement is necessary. In this case, the concrete should be placed compressive load, and on the bars – tensile. The most versatile and technologically simple is a strip foundation – a closed loop of beams under the load-bearing walls that distributes the load on the ground or pillow. For successful construction and long life of the building, it is important to carry out a correct and complete calculation of the reinforcement. To determine the diameter and quantity, there is an online calculator.

What you need to know when calculating?

The following factors are taken into account:

1. The number of bearing walls of the future home and the principle of their location.

2. Brand of concrete (the choice is based on different weather conditions and the corresponding requirements for the ultimate strength).

3. Parameters of the tape:

- width and length (laying);
- height;
- tape thickness (section width).

An additional, but not mandatory parameter may be the size of the purchasing rod for the foundation.

You also need to decide on its class and cross section: in some cases it is necessary to use valves with a diameter of 10 mm and with a ribbed surface. The final strength of the structure will depend on the diameter (d). For example, on a dense non-swelling soil with sufficient bearing capacity from the plates does not require great stability, because the deformation from the house will be less.

The weight of the structure is also important: for the foundation for a wooden house on normal soil, a diameter of 10 mm is sufficient. For a heavy house, which is planned to be erected on weak ground, it is preferable to twigs with d = 14-16 mm. For hardening, a sand or gravel pad is also created. In conditions of solid soil and lack of groundwater, the pillow can be made thinner or used only for the purpose of leveling the pit.

Usually chosen for reinforcement with a cross section of not more than 14 mm, since the tape has a small size (standard height is 0.7 m, and width – 0.3-0.4 m). Laying under the tape foundation is often produced in two belts: in the lower and upper parts in 4 rods. The diameter is calculated depending on the parameters of the foundation and materials of construction. Bending is imposed on the transverse reinforcement located at the bottom of the foundation (cross section). Vertical reinforcement is used to ensure the rigidity of the framework as a whole and to avoid future possible cracks.

As a result of the calculation of reinforcement on the calculator, the following information should be obtained:

1. Perimeter (total tape length).

2. The diameter of the longitudinal bars (the minimum allowable value for SNiP based on the ratio of the content of reinforcement to the cross-sectional area).

3. The number of rows in the lower and upper chord (the minimum number to prevent deformation of the tape).

4. The diameter of the clamps (according to SNiP, the minimum value for vertical and transverse rods).

5. The pitch of the clamps (the distance between the transverse rods in order to avoid frame shifts when pouring).

6. Overlap reinforcement.

7. The length of all the rods.

8. The weight of the reinforcement cage.

Simplified scheme of calculation can be represented as the product of the number of rods in the scheme and the sum of the perimeter of the house with internal walls. Using a calculator allows you to correctly calculate the reinforcement for a strip foundation, which, in turn, will save you from paying for excess material and excess delivery costs in case of its shortage. For the foundation with a pillow, another waterproofing area is calculated.

When calculating reinforcement for strip foundations, they are necessarily guided by the state standard R 52086-2003 and the codes of norms and rules 3.03.01-87 and 52-01-2003 “Concrete and reinforced concrete structures”. The latter indicates the minimum allowable amount, equivalent to 0.1% of the cross-sectional area of the reinforced concrete element.

## Counting example

- Ribbon Foundation.
- Walls – 5 and 6 m. Internal wall – 5 m.
- Let the reinforcement scheme be 4 longitudinal rods d = 12 mm.

1. Calculate the perimeter of the future building: (5 m + 6 m) * 2 = 22 m.

2. Find the total tape length: fold the perimeter from the inner wall. 22 + 5 = 27 m.

3. We find out the total length of reinforcement, taking into account the foundation reinforcement scheme:

a) provided that rods of the required length are purchased: 27 m * 4 pcs = 108 m;

b) under the condition of connecting the segments (considering that the overlap in this case is taken from 1 m, and each of the longitudinal rods has one bond):

- find the number of connections by multiplying the number of rods by the number of walls: 4 * 5 = 20 pcs;
- multiply the size of the overlap by the number of bonds and find out the additional length: 20 pcs * 1 m = 4 m;
- Let us summarize the additional reinforcement with a length calculated on the condition of acquiring the necessary rods: 108 + 20 = 128 m.

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4. Calculate the length of smooth rods d = 10 mm, used in the horizontal transverse bridges and vertical racks. The distance between the jumpers – 0.5 m:

- We calculate the number of reinforcement rings by dividing the total length of the foundation by the distance between the bridges: 27 / 0.5 = 54 m.
- Calculate the perimeter of the 1 ring, taking the distance between the bars for 0.25 m: (0.5 + 0.25) * 2 = 1.5 m.
- Based on these two values, we consider the total length of the rod: 54 * 1.5 = 81 m.
- We take into account overlaps and trimming, adding approximately 10% to the resulting length: 81 m + 10% = 89.1 m. We round up to 90 m.

Since the material is sold by weight, not by the meter, we calculate the mass calculation. The weight of products of metal rolling is regulated by GOST 5781-82, a steel circle – GOST 2590-88. Standards differ in pitch diameters. The calculation table shows the values for core reinforcement:

5. Using the data in the table, we find the mass of reinforcement necessary for arranging the strip footing:

- Ribbed reinforcement d = 12 mm: 128 m * 0.888 kg / m = 113.664 kg.
- Smooth reinforcement d = 10 mm = 90 m * 0.395 kg / m = 35.55 kg.

As joints of parts, it is better to use knitting wire, rather than welding, since during welding, the metal usually changes its structure, and this contributes to its early destruction and, as a result, the building strength decreases with time.

6. Calculate the amount of wire:

At the same time about 0.3 m of knitting wire with a diameter of 0.8 to 1.2 mm is spent on one bundle. The recommended wire material for the reinforcement cage of the foundation is steel. In each connection 4 bundles: 20 pieces (total number of connections) * 0.3 m * 4 pieces = 24 m.

The optimal amount of reinforcement

For a correct calculation, do not neglect the specialized literature. As an example – the manual “Reinforcement of elements of monolithic reinforced concrete buildings”, which states that when the side of the base exceeds the length of 3 m, reinforcing bars d = 12 mm and thicker are allowed, and to evenly distribute the load on the supporting structure – to create 2 reinforcing belts rods of the same diameter.

With a foundation frame height of up to 0.8 m, the minimum diameter of the transverse rods should exceed ¼ of the longitudinal diameter and be greater than 6 mm. With a frame whose height is more than 0.8 m, the minimum diameter should be 8 mm.

Sources: http://tolkobeton.ru/fundament/raschyot-armatury-dlya-fundamenta.html, http://fb.ru/article/183717/armatura-dlya-fundamenta-raschet-armaturyi-dlya-plitnogo-fundamenta, http://stroitel-list.ru/fundament/armatura/kak-rasschitat-kolichestvo-armatury-dlya-lentochnogo-osnovaniya.html