Cracks in the foundation walls
People who want to buy a new property often worry about seeing cracks in the foundations of the coveted home. There are, in fact, several types of cracks in the foundations that do not all have the same gravity:
- There are, among others, minor cracks of shrinkage resulting from concrete drying after pouring. Normally, these cracks are thin, vertical, are not open and do not affect the structural integrity of the house. However, they can represent a risk of water infiltration into the subsoil. It is then more prudent to carry out a preventive repair in order to avoid any possible water infiltration.
- Another type is cracks due to a structural movement of the building, namely the structural cracks. The structural movement may be the result of the subsidence of the soil supporting the house, the heave caused by freezing, a lateral thrust of the soil, a French drain not functional or absent, a bad design of the sole or foundation walls (such as insufficient width of the footing), poor load distribution or poor concrete implementation.
Soil subsidence is the most important factor that can cause foundation cracks. Normally, these cracks are vertical and open, and sometimes there is an offset on both sides of the crack in the foundation wall.
What are the signs of soil subsidence?
- Sagging with the slab on the ground;
- Cracks and shears in the interior finish;
- Wooden floors, on the ground floor and upstairs, which are not level;
- Bulges in the bricks, in the lower part of the siding.
In the greater Montreal area, soils are mostly composed of clay. It is recognized that buildings sitting on clay are the most prone to serious structural movements. Indeed, the bearing capacity of the clay is generally problematic. This low bearing capacity causes differential settlements in the foundation wall.
To evaluate the differential settlement and to know the gravity of the subsidence of the building, it is necessary to level reading testfor foundation walls, made by a specialist. The latter measures the degree of subsidence and analyzes whether tolerances are exceeded or not according to the standard in force. If necessary, he then proposes the appropriate solution. Corrective work for the stabilization of foundations is the driving of piles or the use of anchor plates to secure the two sides of the foundation wall together.
Repair of cracks
To prevent water ingress into the cracks in the foundation walls, cracks in the foundation walls can be repaired with flexible polyurethane. In the case where the cracks are active, reinforcing the foundations with steel anchors is as important as injecting cracks to solidify the concrete and prevent the reopening of a crack. Repairing an externally injected crack will require the installation of a waterproof membrane applied to the foundation wall that has been previously cleaned.