What Are the Current Building Standards Regarding French Drains?

As the saying says, an ounce of prevention is worth a pound of cure. Investing in the installation, maintenance or replacement of a French drain (or foundation drain) will save you a lot of trouble. In the long run, water infiltrations due to weather, broken recreational equipment or sewers can turn into a real nightmare for your wallet and your health.

In addition to reducing the life expectancy of your foundations or affecting the stability of your building by damaging its structure, costly decontamination could be necessary due to mould growth.

All about French drains (foundation drains)

What is a french drain?

Consisting of a pipe and a waterproof synthetic rubber membrane, the French drain is considered the most effective device for water drainage around the foundations. It plays a major role in protecting the building by safeguarding it from water and the damage it may cause.

Who should you call for your project?

French drains should always be installed by a qualified contractor. There are many reasons that could lead you to seek a certified professional for this type of job. Many houses built before 1950 aren't equipped with a French drain. It is also possible that an old installation is no longer able to adequately fulfill its main role, whether due to breakage or the presence of roots that have entered the drain.

In the province of Quebec, for all activities regarding the installation or modification of a French drain, you must do business with a contractor holding a valid license from the Régie du bâtiment du Québec (RBQ).

In other provinces of Canada, such a licence doesn't exist, but you should still make sure that you only hire qualified professionals for this type of job. Indeed, you don't want an inexperienced contractor setting up your foundation drain! Ask for their credentials and referrals from satisfied customers. 

Installing a french drain

First, we must specify that the installation process takes between 2 to 5 days. Warranties for installation, materials and the system's lifespan vary from company to company. The first step will be to assess the area to prepare adequately. The contractor will check with local authorities to find out about the guidelines that need to be followed for this type of project and the terms and conditions when connecting the pipes to the municipal system. 

Next, they will locate the underground facilities and obtain the geotechnical studies. This information will allow them to determine the composition of the soil and help avoid unpleasant surprises. 

They will also ensure the compliance of a safety perimeter if the engineer considers it necessary, i.e. a barricade 90 centimetres high, for example in the case of deep excavations or near public passages such as a sidewalk. Finally, if your house is near a live power line, workers will have to deal with a maximum distance of approach.

Afterwards, they will excavate the building's perimeter, working near the foundations. A good contractor will use tools and techniques that will minimize the amount of damage imposed on your land and prevent water or frost from accumulating at the bottom of the hole during the installation process. In order for the entire installation to be compliant, solid and adhere well to the foundations, it will be necessary to clean and repair them before moving on to the next step.

Next, an elastic membrane will be glued to make the base of the foundations waterproof. The methods and products used will vary depending on the severity of the damage and the company you hire.

Finally, the installation process can start! According to the National Building Code of Canada, the diameter of the pipe must not be less than 10 centimetres. If it's narrower, it will not do its job properly, which is to lead moisture and water away from the house.

Also, it must be installed at the same level as the foundation slab, commonly called the footing, and covered with 15 centimetres of crushed stones or granules of a certain density. If the material is made of particles that are too thin, the drain, which includes a perforated tube, risks clogging. Installing a geotextile membrane around the rock before backfilling the hole is an additional precaution highly recommended by the APCHQ to avoid any clogging.

The last step to consider when installing this type of drainage device will come down to making sure that it empties in the right place, that is, towards the municipal storm sewer. If this sewer does not exist in your neighbourhood, the contractor will have to make sure to lead the rainwater to the combined system by a separate pipe, because sanitary water has to be separated from rainwater.

Also, if it is impossible to create a good enough slope for the water to flow by gravity, the contractor will design a connection around the building. An automatic pump will evacuate the water through a pipe equipped with a valve and installed above street level.