The word of an responding to Nathalie, owner of a house in Laval. She discovered cracks in her foundation walls. She wants to know how to react and stop them getting worse.
Should we be concerned every time we see a crack in a wall of our building?
Any concrete structure is likely to have cracks: this is almost inevitable by the very nature of this material, which is made up of water. As it dries, the water evaporates causing what is known as shrinkage of the concrete which causes microcracks. This concerns both the foundation slab and the foundation walls. This drying process, which usually occurs immediately after placement, can cause completely normal shrinkage cracks. Simple monitoring is required to check their progress. Where this becomes problematic is when these cracks are larger than 3 millimeters because this is the threshold from which a crack is considered dangerous to the integrity of the building.
Should we call in a building expert immediately?
It depends on the type of crack: a large crack usually indicates ground movement (usually caused by differential settlement) and often affects the exterior facing where long oblique cracks are seen. Aging cracks are superficial cracks that appear on foundation walls, in plaster (especially on stone or concrete block foundations) or in slab on grade. Cracks occur first in the weakest places of the walls, that is, at the corners of openings (doors and windows). I like to compare the structure of a building to a human skeleton: if you sprain your foot, you will be careful, but you will not necessarily see a doctor. If, on the other hand, you break your leg, it is in your best interest to see a professional so that they can repair your broken leg. It’s a bit the same with your building: shrinkage or shallow cracks are sprains that should be watched. Cracks larger than 3 millimeters are fractures. However, if a fracture is not treated properly, the joints can become stiff, weak, or irreversibly deformed. It’s much the same process that will happen with your building.
What can be the origins of these major cracks?
Each building is different and only an investigation – and more exactly a structural and / or geotechnical analysis – will be able to determine the causes of these cracks. Among the many possible reasons we can cite, for example, soil subsidence – especially clay soils, high water table, inadequate or too early backfilling, poor concrete composition, adhesion heaving due to frost, a push from the frozen ground, corrosion of the reinforcing bars, poor design…
What are the risks of not treating these cracks in time?
One of the building’s worst enemies is … water! If it does get in, it can create serious problems with humidity and heat loss. The water will attack the reinforcement of the concrete, which will corrode. The freeze and thaw cycles will enlarge the cracks and the entire structure will suffer. In the end, in addition to the risks to the stability of the building, the value of your property will decrease, and the repair bill will increase.
What are the possible solutions?
In addition to ensuring the stability of your building, the foundation walls, as well as the concrete slab, must not allow water to infiltrate. They must therefore be made waterproof. Among the effective methods for repairing cracks smaller than 2-3 mm, there are plugging with epoxy-based injections or flexible products and / or even the installation of a waterproofing membrane. For larger cracks (3 mm and more), it will generally be necessary to reinforce the foundations with steel plates or the like. If the floors show significant signs of tilting, it may be necessary to stabilize the foundation with piles.
How to protect yourself from defects?
The foundation walls are subject to strict regulations in order to represent no dangerous conditions. Moreover, the Association of Professional Construction and Housing of Quebec (APCHQ) indicates that foundation walls “must withstand the load of the building and withstand the lateral pressures of the soil. They must be designed to prevent damage to the building. water infiltration and limit moisture transfer and heat loss. ” Their height, thickness and component are fundamental to obtain solid and durable foundation walls. It is important to have your construction plans and specifications done, as well as your corrective work, by a recognized firm taking out “Error and Omissions” insurance. For repairs, it is preferable to do business with a specialist capable of providing a guarantee on his work. If you have any doubts about the work of the contractor in charge of your work, you can always request work supervision and / or quality control by a building engineering firm. It will ensure compliance with the standards in force and the plans submitted by your engineer. Finally, if you wish, you can request a certificate of conformity which will be an additional guarantee in the event of the resale of your property.
Interview with Claude Guertin, engineer and founder of ProspecPlus Génie-Conseil.