The simple design of the reinforcement plays a significant role in pouring the strip foundation for the building. The strength of the foundation, and hence the durability of the entire structure, depends on the quality characteristics of the reinforcing rods. What kind of reinforcement is needed for a strip foundation?
Foundation characteristics
The construction of low-rise buildings involves the presence of a strip base. Such a foundation is easy to build, moreover, it is the most economical option. The advantage of the tape base is that it can be poured without the use of special construction equipment. In addition, this type of foundation is able to withstand significant loads, which allows the construction of several floors.
Strip foundations can be divided into:
- monolithic;
- prefabricated structures;
- shallow, suitable for the construction of structures made of wood and other light materials;
- deeply buried, which are used in the construction of brick houses with two or three floors.
Depending on the desired result, it is necessary to correctly calculate the amount of concrete required as the foundation pouring, as well as determine what kind of reinforcement is needed for the strip foundation of the house.
Rebar type selection
What reinforcement is used for strip foundations? To date, the most popular types of rods are:
- Steel, with a diameter of at least 5 mm for transverse crossbars and 10 for longitudinal. The strength of the entire tape structure will depend on what brand the reinforcement for the strip foundation is needed. Steel rods of class A are used with a yield strength of 400. Visually, the following differences between the grades can be identified - A 240 has a smooth surface, A 300 has a ring pattern, A 400 has a herringbone pattern. The use of lower quality rods is impractical.
- Fiberglass rods are resistant to corrosion, lack of electrical conductivity. Often such material is used for buildings where it is important to avoid radio interference. The strength of quality rods is not inferior to metal.
For laying the main longitudinal elements of the reinforcement, exclusively bars with a ribbed surface are used, as this guarantees better adhesion to concrete. Smooth rods are used to create side jumpers.
It is strictly forbidden to use the following materials as reinforcement:
- metal pipes;
- mesh netting;
- metal profile;
- iron cables.
Failure to comply with the requirements for reinforcement for the strip foundation can lead to subsidence of the base and further destruction of the entire structure.
Diameter of reinforcement for foundation
The diameter of the reinforcement for the strip foundation determines the subsequent strength of the entire structure. In order to choose the right size of reinforcement, the parameters of the future structure should be taken into account. For example, the maximum diameter with a shallow base and lightweight construction of the entire house will be an waste of money. Often, reinforcement is used for the strip foundation of a house with a diameter of 8-12 mm, this is considered optimal for medium loads.
What reinforcement parameters should be considered:
- the cross-sectional size of the steel bar should be 0.1% of the cross-sectional area of the foundation;
- when calculating the diameter, the length of the foundation tape and its width are taken into account;
- with a foundation length of more than 3 m, steel rods with a diameter of 10-12 mm are longitudinally located, while 5-6 mm are sufficient as a transverse reinforcement.
The diameter is determined individually taking into account the characteristics of the building - building material, dimensions, number of floors.
Standard reinforcement scheme
Once you have decided on what kind of fittings are needed for the strip foundation of the house, you should figure out its installation. For this, there is a universal reinforcement scheme that is suitable for almost any structure on a strip foundation.
- 5 cm high bricks are laid at the bottom of a previously dug trench.
- Large-diameter steel bars are laid longitudinally on the bricks.
- With a pitch of approximately 50 cm, horizontal bridges of smaller diameter are attached to the laid rods.
- Vertical rods are attached to the corners of the formed cells.
- Long rods are tied to a vertical reinforcement.
In order to make the construction as strong as possible, the technology specified in SNiP 52-01-2003 should be observed.
The connection of the rods with each other can be performed by welding or knitting with wire. The second method is much more economical, although its quality is not inferior to classical welding. For its implementation, a knitting wire is used, from which loops are formed. They are threaded through the rods, after which the free edge of the wire is twisted several times. Significantly simplifies the task of using a special hook.
Reinforcement corners
When constructing a reinforcing structure, due attention should be paid to strengthening the corners, which account for a greater amount of the weight of the structure. Corner reinforcement is also made to prevent unwanted cracks or tensile structures.
Corner rods must not be placed perpendicular to each other, their angles must be bent. It is important to ensure an overlap and connect all the bars with radial elements. The overlap of the rods that are used in the corner zone should not exceed 25 cm. If the corners are correctly reinforced during the filling of the trench with concrete, the reinforcing contour will not be destroyed.
Strengthening the various zones of the strip foundation requires the correct calculation of the number of steel rods. Its shortage may lead to the need to purchase the right amount of material, which threatens with a temporary delay in construction.
Calculation of the number of fittings
Collecting a frame from reinforcement for a strip foundation requires careful calculation of the amount of material needed. In order to simplify the task as much as possible and not to use complex calculation formulas, you can simply pre-determine the perimeter of the future design. Then, taking into account the number of rows of steel bars, the number of longitudinal rods is determined.
The amount of transverse reinforcement is calculated by taking into account the height of the tape and the pitch between the steel bars. When calculating the amount of reinforcing material needed, the stock of material should be added to the total amount to form joints between the rods.
Foundation pouring
After determining what diameter of reinforcement is needed for the strip foundation and its bundle, you can begin to fill the foundation itself. The solution is important to mix thoroughly until a homogeneous consistency. If there is no way to do it yourself, you can order a ready-made one.
Filling should be done at a time, periodically bayoneting the solution with a metal rod to avoid voids, which will significantly degrade the quality of the base.
Drying of the mortar should be done naturally for several weeks with periodic wetting of the surface to prevent cracking of concrete. Construction can only be continued a few weeks after pouring.
The need for reinforcement
Some builders question the need for reinforcing the strip base, motivating it with the fact that high-quality concrete already has sufficient strength. However, it is not. The base without additional reinforcement is unstable to soil movements.
The reinforcing frame is used to distribute the load on the base, as different parts of the house may have different weights. Especially such a design is needed for a strip foundation, which will be support for heavy brick construction of several floors.
Material purchase
You can start buying building material. if you have finally decided what kind of reinforcement is needed for the strip foundation. Rarely, steel bars are measured in linear meters, as in calculating the required amount for construction. Sellers calculate the amount in kilograms.
In order to correctly calculate the required weight of building material, experts recommend using the tables from GOST 5781-82 or GOST 2590-88, which indicate the weight of a unit of steel bar. The numbers in both documents are the same, so the use of one or another GOST depends only on personal convenience.
A necessary tool for work
With independent construction of a strip base, the following tools may be required:
- the water level that is used when installing the ditch, it will help align the walls in a strictly vertical position;
- for tying steel rods, pliers and wire cutters or a special knitting tool that will allow you to complete work faster may be needed;
- a grinder or grinder equipped with diamond cutting wheels for cutting steel rods;
- to assemble a wooden formwork you will need a hammer, a screwdriver, as well as long nails or screws;
- for self-mixing of the concrete mortar, you may need a concrete mixer, which will achieve uniform consistency, and also significantly save time and effort, if not, you can order the ready-made mortar with delivery or knead manually using a large trough and a shovel.
In addition to these tools, auxiliary ones may be needed - buckets, trowels, shovels, a construction wheelbarrow. Often they are acquired as needed.
The competent device of the frame for the tape base can significantly increase the operational life of the building. It also eliminates the need for frequent repairs, which may be necessary in connection with the destruction of an incorrectly constructed building.