DIY strip foundation repair step-by-step instructions
In detail: do-it-yourself strip foundation repair step-by-step instructions from a real wizard for the site my.housecope.com.
Restoring the foundation is not difficult, but time consuming.
You can strengthen the crumbling concrete tape in the following way - pour an additional layer of concrete with good reinforcement around it around the entire perimeter, that is, make a kind of sarcophagus.
At the same time, the new fill must take on the main load and prevent further destruction of the old foundation. To do this, it is necessary to ensure a strong adhesion of the new and old structures. The excavated foundation must be thoroughly washed, otherwise the new fill will not grab with dirty concrete. It is also important to provide reliable reinforcement. For this purpose, I decided to pull the reinforcement cage on both sides of the tape with jumpers-studs passing through the old foundation, for which I made through holes in the tape with a pitch of 50-70 cm using a perforator with a long drill.
The harvested reinforcement rods were first bent at right angles at one end. Then he inserted the rod into the hole and bent the other end. The folded ends on both sides of the tape were tied to the reinforcement cage.
Thus, the frames on both sides of the tape were connected by S- or U-shaped bridges. Each bend of the lintel should be 40-50 mm from the foundation surface. In my case, the reinforcement cage is made of a metal mesh (4 mm thick) with a cell size of 100 * 100 mm, connected in the upper part with reinforcement bars of Ø 8 mm and tightened with jumpers.
The height of the excavated part of the foundation is about 70 cm.If the formwork is placed entirely at once, then it is unrealistic to lay concrete in such a narrow and high form with high quality. Therefore, I decided to pour concrete in two steps with the vertical rearrangement of the formwork.
Video (click to play).
For the manufacture of the formwork, I used flat slate lindens. This material is the best suited for this purpose: it is resilient and durable, and the surface of the finished filling is flat and smooth. But the most important thing is that the slate easily moves away from the hardened concrete, and the formwork is easy to disassemble. There is no need to lay polyethylene or glassine, as is done in the classic formwork made of boards or plywood.
The volume of concrete is small, so you can work without using mixers and concrete pumps. The concrete mixer stands next to the formwork, the mixture can be easily thrown with a shovel.
For a quick assembly of a flat slate formwork, I used a little trick. The two panels were temporarily but reliably connected to each other with an ordinary clamp. The main thing is not to forget, after pouring, until the concrete has hardened, to remove it in time.
On the second land, I removed the lower formwork and raised it higher. Since you have to make three tapes in turn, there is no need to wait for the concrete to harden: while the first pouring takes hold, I proceed to the second, and so on. Three tapes on two floors: six days and you're done.
Work is done. The result is a powerful (even too much) new strip foundation, which will stand, uh ... enough for our century!
The result obtained has a small drawback. In the classic version of a stone fence, the width of the foundation should not be greater than the thickness of the brickwork. If these proportions are not observed, the entire fence looks inharmonious. But in my case, there was no alternative.
I will proceed as follows. First, I will fill the foundation up to its upper edge, and finish the horizontal shelves with wild stone.
I tried to analyze why the foundation began to deteriorate so quickly and what my builders did wrong.Carefully examining the structure, I came to the conclusion that, in addition to the banal non-observance of the proportions of the concrete mixture and its poor mixing, there are two more reasons.
Firstly, the workers used unsifted sand with a large amount of clay impurities, which significantly reduces the grade of concrete. In addition, poorly mixed concrete quickly collapses during freeze-thaw cycles in early spring. Secondly, 'the builders - used too liquid concrete, believing that in this way it is possible to fill all the voids 8 of the formwork, and not suspecting that the strength of the structure in this case is sharply reduced.
Well, as they say, if you want to do well - do it yourself!
Having dug up all three strips of the foundation around the perimeter, they found an unsightly picture. Almost two-thirds of the tape's volume simply disappeared, turning into a pile of small pieces.
1.To clean the old foundation, it is better to use a pressure washer. We not only clean the surface of dirt, but also knock out all the gravel, which is weakly adhered to the old concrete, which means that it will not give good adhesion.
2.To tie the frames with reinforcement rods, I made through holes for them in the tape with a pitch of 50-70 cm. For this, I used a hammer drill with a long drill.
3. S- and U-shaped crosspieces were connected to the reinforcing bar with annealed wire. My wire is thicker than usual, and the standard tool for twisting it did not fit. I had to work with pliers.
4-5. Finished reinforcement cage.
6-7. Armopoyas and mesh hug the entire foundation around the perimeter, forming a closed loop.
8. On this side, the formwork is fastened in the form of supports from metal corners driven deep into the ground.
9. And here the short support pegs are simply pinned down with bricks used as struts.
10. Until the concrete reaches a normal strength, it must be kept wet. I watered it 4-5 times a day ido, and after removing the formwork.
11-12. In some places, the distance between the old foundation and the formwork is no more than 7-8 cm. If the mixture is not vibrated, the concrete will not fill all the voids - and there will be many pores. For high-quality concrete placement, I used a deep vibrator.
Cracked foundation The builders poured the strip foundation, and after a while cracks began to appear in it. It's good that they haven't started building the house yet. What should we do? Is it possible to fix everything? If so, how many floors will such a foundation withstand (we planned three)?
It's good that you saved your family budget from wasted expenses. If the foundation cracked without load, then imagine what will happen after the application of 20-30 tons, which weighs a decent dacha. Of course, these cracks will widen and the structures will sag. But in all this there is one positive moment: you must understand why this happened, and fundamentally exclude the very possibility of repeating these mistakes. There may be several of them. First of all, it can be low-quality cement or cement of the wrong brand. Then, the sand could not be clean, but with an abundant inclusion of clay. The wrong dosage of the components could very well lead to your unfortunate results. Incorrect mixing of components in the wrong sequence is also a possible cause of cracked foundations. And of course, this concrete mixture had to be thoroughly compacted with a deep vibrator. Did you have it at the construction site? What weather was your foundation poured in? Perhaps it was extremely cold or, on the contrary, the sun was shining mercilessly and you did not hide the foundation from the influence of these factors? Only after analyzing all these reasons can we take on a new foundation. And this one will smash well a tractor with a mounted hydraulic hammer.
A strip (continuous) foundation is a foundation that runs under the entire perimeter of the walls and consists of precast concrete blocks, monolithic reinforced concrete, concrete, brick or rubble concrete.By itself, the strip foundation has a fairly long operational life, sometimes reaching 50 years or more. First of all, it depends on the high strength and solidity of the structure. However, the adverse effect of external factors can lead to a significant decrease in strength parameters or to its partial destruction. In such a case, it is worth repairing the tape base.
First of all, it is required to determine the causal relationships of the violation of integrity in general and its grounds in particular.
Possible causes of deformation and crack initiation are:
excessive moisture caused by excessive precipitation and, as a consequence, overvoltage of the soil;
insufficient depth of the bookmark;
heterogeneity of the structure of the supporting or underlying soil layer of the base;
insufficient frictional resistance caused by clayey soils highly moistened with water, as a result of which the axis shifts along with the structure;
destruction of masonry solution due to the impact of aggressive or underground waters of sanitary-technical communications;
penetration into the base of surface waters due to the absence or violation of the integrity of the blind area;
excessive load and insufficient penetration into the ground;
freezing of the base caused by poor deepening during construction work and improper cutting of the soil near the house;
clogging or disruption of the drainage system, which causes an excessive rise in the groundwater level and softening of the soil layer;
change in the permissible loads for superstructures of additional parts of the building.
The malfunction of the base is determined by the presence of cracks on the main walls of the house.
As a rule, they are in places of partitions and their abutment to walls.
Strip foundation diagram.
Before starting any repair work, you should find out the moment when the uneven shrinkage is completely finished.
To do this, control beacons (gypsum linings) are installed across the detected crack. They are firmly fixed on both sides of the crack on the load-bearing parts of the wall (with the calculation of 1 beacon per 2-3 mm crack). Lighthouses are made of plaster mortar (width - up to 8 cm, length - up to 5 cm, length - up to 30 cm) and stacked on well-cleaned places.
After 3 weeks, in the absence of changes in the lighthouses, the crack formation process can be considered complete. When lighthouses are destroyed, it is necessary to find out the level of intensity of uneven precipitation. In this case, simultaneously with the beacons, a special lever device is installed on the cracks, showing the size of the sediment in millimeters.
After determining the nature of the destruction and the causes of the appearance of cracks, it is necessary to choose the main method of its strengthening, on the basis of which further repairs will be carried out.
Repair of the strip base is divided into several stages, and subsequently, after all the work has been carried out, it should not harm the general structure of the building:
Thorough cleaning of all surfaces of the strip foundation around the entire perimeter from dirt and old plaster. First of all, the basement is cleared from the ground at a sufficient distance for repair work.
At this stage, the repair will require a certain set of tools, namely a jack, a pole with a diameter of 11-18 cm, plank gaskets 50-60 mm wide and 50-80 cm long (they can be replaced with bars of the same length, but 80-120 mm thick ) and temporary chocks for installation under the lower foundations (crowns) of the house.
Then, having retreated from the main building by 1-1.2 m, you should start disassembling the destroyed area and install a jack on a special gasket under the lower crown of the house.
After determining the level of the position of the lower rim next to the jack for its subsequent release, a chock or a piece of timber is installed. A similar operation is performed at the corners, at the intersection and destruction.
Repair with the belt folding principle at the replacement stage will require the preparation of the following tool: pick, wedges, sledgehammer (or ax), steel scrap and bolt.
Disassembling bricks can be done manually with a crowbar or pickaxe, striking the horizontal joints from top to bottom.
When executed from cement mortar, wedges are used, hammered with a sledgehammer or an ax into horizontal or vertical masonry seams;
Work is carried out in a similar way when disassembling rubble.
Pile foundation diagram.
Having completed the repair and partial reconstruction of the cracked base of the strip foundation, they proceed to the formation of horizontal waterproofing, which can be performed by partially cutting the wall. The base is carefully dug out in short sections to its sole, after which it is trimmed, and a waterproofing material is laid in the gap formed. Horizontal waterproofing is also installed at the joints with the walls. In addition, various water drainage systems (drainage) are being constructed.
There are two main methods of horizontal waterproofing:
Scheme of pile and slab foundations.
The first method is based on the use of roofing material (rolls of polymer-bitumen waterproofing), which is placed in the bottom and poured with concrete mortar. To create greater strength and reliability, sheets of roofing material are coated with hot resin.
The second method is more effective than the first, and consists in the use of specialized waterproofing materials, for example, such as penetron. It is a special mixture that penetrates deep into concrete, making it waterproof.
For easy and quick waterproofing work, you can use specially made sprayers, with which the waterproofing layer is applied directly to the foundation.
Due to its structure, sprayed waterproofing repeats all the unevenness of the foundation surface. Subsequently, a reinforcing layer of geotextile material is applied, which helps the waterproofing to perform its protective functions.
After the completion of the waterproofing work, the damp walls are dried and vertical waterproofing is performed.
Slab foundation diagram.
The repair of vertical waterproofing involves a similar laying of waterproofing materials, for which a properly prepared base and preliminary drying of the areas remain important conditions to obtain the maximum effect of the work carried out.
Modern methods of draining basement walls, which do not require preliminary excavation, include the method of penetrating waterproofing using special substances that can penetrate into the wall and crystallize in microcracks. This will make it possible to prevent unnecessary filtration of the water.
Finally, you can start pouring concrete into the new structure. The best option would be to use factory-made concrete, as this mix will be of better quality.
Repair of the strip basement can also be done by strengthening the old one. Typically, this method is used when the base of the building is skewed as a result of the difference in pressure applied to different areas.
What tools should you use? Mainly:
level;
roulette;
trowel;
concrete mixer;
puncher;
capacity;
putty knife;
brush and others, the need for which arises in the process of work.
It is carried out by increasing the area of its base according to a certain scheme:
digging a trench near the house along the base;
preparation of the old one for joining with a new way of drilling holes for grooves and fittings;
the formwork of a new base is being carried out;
the prepared reinforcement cage is connected to the reinforcement inserted into the house;
everything is poured with concrete mortar;
after the solution dries, the foundation is buried.
In case of violation of the rules for laying a part during the construction of a house, which led to its subsequent deformation, it may be necessary to further expand and deepen the basement base.
In this case, the repair will consist in expanding one or more sides of the house with a solution of concrete or reinforced concrete. Expanding the foundation with bricks is not recommended due to its hygroscopic properties. First of all, the areas most loaded with masonry (corners, inter-window supports) are subject to replacement.
Expansion repairs are based on the excavation of special sockets for a good connection between the old part of the basement and the new one.
In total, it is possible to determine that repair is necessary at the slightest manifestation of various cracks on its surface. Their danger, as a rule, lies in the ingress of water through them, which, freezing in winter and then thawing, causes further destruction of the base of the strip foundation along the entire perimeter of the house.