Do-it-yourself strip foundation: reinforcement rules

- one of the most common. It is easy to manufacture, with its help a variety of building configurations are easily implemented. On it you can build a house on several floors or a small bath. To give the concrete greater strength, and the base of greater reliability, the foundations are reinforced with steel bars of various configurations.

In the presence of steel elements in the structure, it is no longer concrete, but reinforced concrete, and its strength is many times higher. These works are not the easiest, but the work of the brigade is quite expensive. Moreover, it is not a fact that they will do the right thing: for them, this is just another order, and for the owner - a favorite home (bathhouse, cottage, etc.). Therefore, reinforcing the foundation with your own hands is an excellent choice. There is only one caveat: if the soils are complex, the groundwater is high, and even the structure will be heavy, it is better to order the calculation of the foundation in a specialized office. So you will have a guaranteed correct and reliable foundation for the house in such difficult conditions.

The strip foundation is one of the most widely used in our country.

The peculiarity of the tape bases is that their length is many times greater than the width and height. The load from the building presses on the foundation from above. It turns out that in this case the top of the tape is compressed, and the bottom is stretched. Since cracks form in the monolith during tension, the lower reinforcement belt is required to ensure its integrity.

A strip foundation of any height almost always has two reinforcement belts - upper and lower

On the other hand, from below, forces periodically press on the tape, which appear during soil heaving. Here the picture is opposite - the bottom of the foundation is compressed, the top is stretched. And again, cracks form in places of tension. Therefore, to prevent their appearance, the upper edge must also be strengthened.

Tellingly, the middle of the base is practically not loaded, and therefore, whatever the height, the middle belt is rarely made.

If you need to greatly deepen the foundation, it is advisable to order a professional calculation. Then the experts will tell you exactly how many belts will be required for the structure to stand for a long time, from which bar it should be made.

It turns out that two reinforcement belts are required for the strip foundation: one at the bottom, the other at the top. Moreover, to protect against corrosion, they should be located 5 cm deep from the edge.

What fixture to use

Now you need to understand in which direction reinforcement is needed, how thick it should be. It depends on the distribution of loads, and they are distributed in this base in such a way that most of all the effects fall on the longitudinal bars. Therefore, they must be strong and corrugated - class AIII. On hard and non-porous soils for structures of small mass, reinforcement with a diameter of 12 mm is used. On more difficult soils or for heavier walls, 14 mm is used. To be safe, stack 16 mm. Large diameters in low-rise construction are rare, although 20 mm are sometimes laid.

The vertical and transverse bars of the reinforcement in the strip foundation are loaded weakly. For the most part, they are needed to give shape and stabilize the structure. Therefore, a smooth bar with a diameter of 6-8 mm is used for vertical and transverse racks. Its strength is more than enough to perform these functions.

Reinforcement step of strip foundations (according to SNiP)

When placing all the bars, a key condition is observed: there must be at least 5 cm of concrete from the edge to the steel. Only in this case, the reinforcement is protected from corrosion (water and oxygen no longer penetrate to such a depth). But it is also impossible to deepen the belts too much: greater forces act on the surface layers than closer to the middle. Therefore, reinforcement should not be hidden much deeper: it will not fulfill its tasks. A distance from the edge of 5-6 cm is the best option.

For a strip foundation, it is necessary to determine the number of longitudinal bars in each of the belts. According to SNiP 52-01-2003 (clause 7.3.6), the distance between them should be no more than 400-500 mm.

But the width of the tape for small buildings, which is a bathhouse (a one-two-story house too), is rarely more than 40 cm. see. That is, 2 longitudinally laid "reinforcement" is quite enough.

Since the main loads occur precisely along the belt, it is desirable to lay solid steel elements without joints. On average, the length of the reinforcement of the required class is 6-11 m. This is enough for most houses and baths. Inconvenient for delivery, but the foundation will be reliable. Moreover, take the rods at least 1.5 meters longer: they will need to be bent when passing corners. This will make it reliable and durable.

The next step is to determine the pitch for the location of the uprights and crossbars. We will refer again to SNiP. Only this time point 7.3.7 is needed. It states that the transverse reinforcement in the strip foundation should be placed at a distance of no more than 300 mm from each other. There is some contradiction here: practitioners say that on normal soils it is enough to place the crossbars no closer than 500 mm. Moreover, even a brick house on such a basis will stand normally. Actually, it's up to you. If you don't know what to do, order a calculation. Or play it safe and put it through 300 mm. The foundation is the part in which it is better to overdo it. It'll be cheaper. Moreover, a smooth bar is not so expensive.

Sometimes the vertical and transverse posts in the strip foundation are made bent. This further increases its strength and reliability. And some, reinsured, stack three bars ...

So, we decided that the laying of reinforcement in a strip foundation (up to a meter high and up to 600 cm wide) is necessary in two tiers: one 5 cm above the bottom edge, the second - 5 cm below the top. Each belt will have two corrugated longitudinal bars with a diameter of 12-14 mm. Vertical posts and transverse reinforcement go through 300-500 mm and make them from a smooth bar of 6-8 mm.

Reinforcing the corners of the strip foundation

The corners of any building are places where different load vectors are connected. That is why it is so important to perform the reinforcement of the corners correctly. A simple connection of two bars is unacceptable here: it is not able to transfer and distribute loads. This section requires a special approach and special schemes for laying reinforcement.

For their proper strengthening, it is necessary to use bent elements. It is desirable that they be a continuation of the longitudinal bars, and "go" around the corner by 60-70 cm (see the diagram on the left).

If the length is not enough, use separate elements bent in the form of the letter “G” - clamps. Their sides must be at least 50 bar diameters (if you use 12 mm, then the sides must be at least 12 mm * 50 = 600 mm, for a 14 mm bar - 700 mm). How the reinforcement is laid in this case is shown in the right diagram.

Please note that in the corners, vertical and transverse belts need to be placed twice as often: the reinforcement step here is half as much.

The strengthening of places where tapes under internal partitions depart from the main perimeter requires no less attention. The abutments of these walls also require the use of bent elements according to the same rules. The reinforcement diagram on the left shows how to lay the bars with a margin of length, the diagram on the right shows how to use a separate L-shaped clamp.

Now you know how to properly lay the reinforcement in the corners. By following these rules and implementing the schemes, you will create a solid foundation that will withstand both the static load from the building itself and from heaving forces. And your building will never give cracks in the corners, which are very difficult to deal with.

When and how to install fittings

Reinforcement of the strip foundation begins after the formwork has been assembled and installed. Longitudinal and transverse guides must be somehow connected. There are two methods: welding and wire knitting. Welding is faster, but it is not recommended to use this method: the welds corrode faster, and the result is too rigid a structure that resists loads worse. Therefore it is desirable

We decided on the connection method. Now you need to choose where to assemble the frame. There are two methods:

Both methods are used. The second one is probably more convenient - it is inconvenient in a narrow trench. In addition, it is possible to damage the film, which is often lined with the bottom and walls of the formwork (to minimize concrete leaks and prevent it from drying out).

But with a long length of finished modules, it will be necessary to somehow deliver a very difficult and rather flexible structure to the place, and even lower it evenly to the bottom of the trenches. There is no need for technology here. So, too, there are difficulties and disadvantages.

Results

Do-it-yourself reinforcement of a strip foundation is not an easy task, but quite real. One person will have to work for a long time, but this option is also real for small houses (country houses or baths).