There are several types of cracks in foundation walls, which do not all have the same severity:
1- Among other things, there are minor shrinkage cracks that result from the concrete drying after pouring. Normally, these cracks are thin, vertical, closed, and do not affect the structural integrity of the house. However, they can pose a risk of water infiltration into the basement. It is therefore more prudent to carry out preventative repairs to avoid any potential water infiltration.
2- Another type of crack is one caused by structural movement of the building, namely structural cracks . Structural movement can result from subsidence of the soil supporting the house, frost heave, lateral soil pressure, hydrostatic pressure , a non-functional or missing French drain, poor design of the footing or foundation walls (such as insufficient footing width), improper load distribution, or faulty concrete placement or the presence of pyrite. Structural cracks must be examined by a structural engineer to determine the extent of the damage to the building's structure.
Significant movement in the foundation wall
Soil subsidence is the most significant factor that can cause cracks in the foundation . Normally, these cracks are vertical and open, and sometimes, a displacement can be seen on both sides of the crack in the foundation wall.
What are the signs of subsidence?
- Subsidence relative to the slab on 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 facing;
- Cracks in the slab on ground.
In the greater Montreal area, the soils are predominantly clay . It is well known that buildings built on clay are the most susceptible to serious structural movement. Indeed, the load-bearing capacity of clay is generally problematic. This low load-bearing capacity causes differential settlement in the foundation.
To assess differential settlement and determine the severity of building subsidence, a leveling test of the foundation walls is required. This test must be performed by a specialist. The specialist measures the degree of subsidence and analyzes whether or not it exceeds the permissible tolerances according to the applicable standard. If necessary, they will then propose the appropriate solution. Corrective work for foundation stabilization includes driving piles or using tie plates to secure the two sides of the foundation wall together.
Repair of cracks
To prevent water infiltration inwards through cracks in the foundation, cracks in the foundation walls can be repaired using a flexible polyurethane. In the case where the cracks are active, the reinforcement of the foundations with steel anchors is as important as the injection of the cracks to solidify the concrete and prevent the reopening of a crack. The repair of a crack injected from the outside will require the installation of a waterproof membrane applied to the foundation wall which will have been cleaned beforehand.
Horizontal crack in the foundation wall
