How to waterproof house foundations from the outside

Do you have a finished basement that you want to protect from water infiltration without having to clear the walls to access the foundations? You will need to waterproof your house foundations from the outside. This will provide excellent protection against water and humidity to your concrete foundations while keeping your basement intact.

Our excavation specialists explain how to waterproof house foundations from the outside.

1 – Excavate the ground around the perimeter of the foundations

The first step to waterproofing exterior foundations is to excavate the soil around the entire perimeter of the building. It is necessary to dig down to the base of the concrete footing to gain access to the entire foundation.

In some cases, this task involves removing concrete sidewalks, decking and landscaping. It is therefore necessary to get an occupancy permit beforehand. If you want to limit damage to your property, you should consider hiring a company that offers residential excavation service. These companies are usually equipped with mini excavators for precision digging.

If the property you want to waterproof is a condominium or a building with several units, the fastest and most practical solution will be to deal with a company that offers a multiplex building excavation service.

2 – Seal all cracks in the concrete

You will have the best view of your foundations’ condition once they are exposed. You will be able to inspect them for cracks or defects such as honeycombing, which is the cause of many water and moisture problems in basements. If you see any defects, you will have to deal with them to make your foundation walls waterproof again.

Techniques such as injecting epoxy resin or polyurethane are ideal for sealing cracks in concrete and will prevent water from flowing freely between the exterior and interior of the foundation.

3 – Attach a waterproofing membrane to the outside of the foundation

Concrete used for building foundations is a relatively porous material. This means that even if it has no cracks, it can let water and moisture in if the soil it is in contact with is saturated with water. To prevent water from reaching the foundation, a waterproofing membrane must be attached to the outside of the foundation.

Different types of membranes can be used for foundation waterproofing in Quebec. There are synthetic rubber (elastomer) membranes and “honeycomb” membranes, which are composed of two layers separated by air pockets. The latter reduces the pressure of water against the foundation and provides some drainage.

For maximum efficiency, you should also cover the footing with the membrane of your choice. The membrane also needs to extend above ground level.

4 – Backfill the trench dug around the foundations

Once the waterproofing membrane has been well secured, simply backfill the trench dug around the building.

Before filling this huge hole, why not take the time to check the condition of your foundation drain? You could cover it with clean gravel and a geotextile to make sure that water drains properly rather than reaching your freshly waterproofed foundation.

Excavation Chanthier, your exterior foundation waterproofing partner

In short, exterior foundation waterproofing is done in 4 steps: excavation, sealing concrete cracks, installation of a waterproofing membrane and backfilling. These large-scale projects are difficult to carry out, which is why you should rely on professionals.

If your property is located in the Greater Montreal area and you want to make sure that the excavation and backfill work will be done in a clean and meticulous manner, you can trust our excavation services. At Excavation Chanthier, we are proud to hold an RBQ licence that testifies to the quality of our work.