Horizontal cracks in foundation walls reveal lateral movement caused, among other things, by the lateral thrust of the soil which exerts a force perpendicular to the foundation walls.
All of this cracks horizontales peuvent se retrouver dans les murs de foundations en blocs de béton ou en béton coulé. Souvent, ces fissures sont accompagnées d’un déplacement des murs vers l’intérieur du bâtiment.
Lateral push (ground)
When the lateral force of the soil is large enough, then there may be partial or complete collapse of the foundation wall. Concrete block walls are less resistant to lateral soil force than poured concrete walls.
In general, foundation walls in concrete blocks or poured concrete are not reinforced or not sufficiently reinforced (steel reinforcements) to be able to resist high lateral loads from the ground or others.
The lateral thrust of the soil is greater in frost-prone soil such as clay, especially if there is an absence of an adequate drainage system behind the foundation or retaining walls. It is the same in places where the exterior development does not keep surface water away from the foundation walls and also in the case where the ground rises with a slope, behind the foundation walls, such as houses on the side of the foundation. mountain. Often these buildings show signs of movement and sag towards the valley, river or lake due to the movement and sliding of the ground downward.
For this reason, it is very important that the backfill – behind the foundation walls – is made up of frost-resistant and draining materials such as gravel. Also, the drainage – at the base of the foundation walls – must be functional and efficient. Finally, the foundation walls must be reinforced to resist the lateral force of the soil.
Sometimes in the foundation walls, we find vertical and/or diagonal cracks. These cracks may be shrinkage cracks if they are thin and closed.
In the case where the cracks are open, then we must consider the hypothesis of subsidence of the ground under the foundation walls. To determine the extent of the subsidence of the ground on the structure of the building, a level measurement is required by a structural engineer who may possibly recommend driving piles around the perimeter of the foundation walls in order to stabilize them. .
The presence of star-shaped cracks and the uprising for the slab on ground in the basement are normally linked to the existence of a high hydrostatic pressure under the slab on ground, due to poor drainage around the building or the presence of pyrite in the backfill below the slab on ground.
© Fissures horizontales dans les murs de fondations
