Foundation repair methods

Any building serves for a long time if it has a well-made and reliable foundation. But sometimes troubles happen when the foundation collapses, gives sediment or cracks. The reasons can be very different. The most common are associated with soil characteristics when the type of soil, its moisture content, and the freezing point is not correctly determined. As a result of this, mistakes are made when choosing the type of foundation, its bearing capacity, and construction technology. Another reason is the old age of the building. Its foundation is simply not designed for the effects of buildings under construction next to modern vibration loads.

 

Pier and beam foundation repair cost

 

Pier and beam foundation repair costs generally range between $4,000-$6,500. If you’re simply having your foundation re-shimmed, the price would be closer to $2,500-$3,500, depending upon your home’s square footage.  Of course, if you’re repairing a very large house that has a pier and beam foundation, the price would go even higher. In fact, if it is seriously damaged, it could well exceed $10,000. And remember: It’s one thing to install ¼” steel shims to stabilize girder beams under a house, and quite another to install concrete piers (or pilings) all the way around a structure.

 

Why is the foundation destroyed?

 

Foundation repair using screw piles.

In order to choose the right technology for the restoration of the foundation, first of all, it is necessary to determine the causes of its destruction. Among the main ones:

  • increase in load;
  • mistakes made during the design of the building;
  • loss of waterproofing properties of the masonry and subsequent deformation;
  • damage to the base or the use of low-quality materials for facing, the absence of a second layer of waterproofing at this level;
  • incorrect placement of waterproofing relative to the blind area (10-15 cm lower);
  • damage/destruction of the blind area;
  • the construction of new buildings at a depth nearby with existing ones (transition, garage, basement, etc.);
  • soil freezing followed by thawing;
  • soil deformation and, as a result, loss of foundation stability;
  • accidents on utility networks laid nearby;
  • change in groundwater level.

The simplest problem to solve is the lack of a waterproofing layer. It is solved by punching a rectangular hole in the base (height — approximately like two bricks) and laying a double layer of waterproofing (with the preliminary alignment of the base). The hole is laid with a brick.

Other problems are solved in a more laborious way.

 

Foundation repair options depending on the type of destruction

 

main reasons for the destruction of foundations

Leaching of concrete/crystallization destruction of concrete. Reason: constant exposure to water with a prevailing content of salts and alkalis. In such a situation, the main thing is to divert aggressive waters or to reduce their level of exposure using a drainage system. After this, the soil around the foundation is removed up to the base, cleaned, and the recesses are filled with a solution. At the same time, brickwork is installed vertically, which is parallel to the foundation. In this case, the brick is isolated from the base with roofing material and impregnated with bitumen. After the repair is completed, the voids are filled with greasy clay.

Bundle. Reason: excessive load on the base (for example, due to a superstructure), insufficient strength of dressing in masonry, or lack thereof at all. In this case, the foundation is restored by filling cracks with a solution or by installing additional beams that will take on part of the load.

Gap (in height). Reason: increased groundwater level, damage to the blind area or errors in the construction of the foundation (for example, the use of frozen ground for backfilling). The way to fix the problem is to remove the unsuitable soil, filling the area of ​​the gap with a solution, and the sinuses – normal non-porous soil. If necessary, arrange a drainage system and restore the blind area.

 

The main methods of strengthening and repairing the foundation

repair steps foundation

Almost all existing technologies are based on increasing the area of ​​the base, due to which the load on the soil is reduced. This can be achieved by installing reinforced concrete clips or banquets (there are single or double-sided) with the mandatory preliminary strengthening of the foundation with unloading beams.

To exclude the option of the destruction of the wall, the base is not completely dug, but in separate sections with a length and a width of 1.5-2 meters. After that, metal pins are driven into the foundation (or installed into pre-prepared holes), the formwork is made and the broadening is concreted, as well as banquets that are adjacent to the faces of the foundation. In punched openings, stops for hydraulic jacks are installed – steel beams. Using a jack, the soils at the base of the expandable sections are crimped. After the jack is removed and the banquet is poured with a solution. Work in the next section does not begin until the previous one is filled up.

Work with a complex foundation. A different technology is used in the reconstruction of the strip foundation when its global strengthening is required. In such a situation, with the help of fittings, it is rearranged into a tiled one. Particular attention is also paid to strengthening the old stone foundation – in this case, an over-stressed reinforced concrete clip is created to remove part of the load from the base. Thus, not only increases the rigidity and depth of the existing foundation, but also the base is protected from groundwater, and the soil is compacted.

Chemical methods. In parallel, chemical methods are used to improve the condition of the soil by introducing various chemical reagents, which are especially effective for errors in the design of the strip foundation (device to a shallower depth compared to the freezing point of the soil). Hydrochloric acid and urea resin were originally used as reagents. However, due to the negative impact on the environmental situation, these reagents are increasingly being replaced with silicates (carbon dioxide and liquid glass are pumped into the soil under pressure, Portland cement is used).