Protecting your building from heavy rains
How can you protect your home from flooding during storms? Several actions can be taken to adapt your building and limit the impacts and potential damage caused by heavy rains.
Ensure the resilience of buildings
Like most cities in the world, Montréal faces unusually intense rainstorms that can generate rapid rainwater accumulations on roads and risk flooding homes or causing sewer backups.
Homeowners are strongly advised to identify potential vulnerabilities in their home to make sure it is adequately protected. The most effective measure to avoid the impacts of heavy rains is to ensure the resilience of buildings and prevent water from seeping in. The community is central to this strategy and to the actions that must be taken to increase the resilience of private buildings.
Summary of potential building vulnerabilities during heavy rain and key adaptation measures to protect against back-up and flooding.
Checklist
All building types
- Check your home for entry points that may facilitate water surging in from the street, such as a downstairs entrance.
- Make sure you have properly working check valves (also known as backwater valves or backflow preventers) on plumbing fixtures located below street level. It is essential that there is a check valve for all drains on the floor or for plumbing equipment (for example: toilets, taps, etc.)
- If possible, clear debris that could block the entry of water from the sump on the street near your residence in order to facilitate the collection of surface runoff.
- In the basement, make sure floor drains are clear and valuables are in watertight containers.
- Make sure that the openings in the building are watertight. For doors and windows located under or at street level, there are a number of permanent or temporary protection measures on the market that help reduce the risk of being flooded, such as watertight partitions and removable cofferdams, etc.
Homes with a countersloping garage entrance
This type of home is more vulnerable to flooding when water accumulates on the roadway, because the entrance is located below street level. As a result, water can enter the building more easily.
Here are the 4 primary protection measures to consider:
Installing a speed bump at the back of a driveway leading to a parking space below street level can be a sufficient and inexpensive measure in some cases. Make sure that the slope leading to the driveway is long enough for a vehicle to negotiate the speed bump without catching its underside.
Installing a watertight garage door, and an adjoining entrance door, if applicable, is a measure that has been successfully tested in Montréal. It may provide effective protection against the risk of flooding and let you keep your garage.
See the watertight door model (in French) tested by Écohabitation, the city’s partner in this pilot project.
Find out about the prerequisites for installing a watertight garage door (in French), including maximum protective water level, plumbing modifications, etc.
Backfilling the entry is a measure that definitely eliminates the risk of surface flooding. You should, however, check with your borough to find out the current regulations and requirements in effect.
See Ecohabitation’s page (in French) on backfilling driveway for more details on what’s involved. Don’t forget to check with your borough for current regulatory requirements.
A cofferdam is a removable barrier that can be installed in front of an opening during heavy rain to prevent flooding from accumulated street water. As with a watertight door, the idea is to keep water out.
Cofferdams, which are popular in Europe, could be an effective solution to protect your home. The city is closely studying this technology to assess its usefulness in Montréal’s context.
With the exception of cofferdams, these measures are eligible for financial support from the city under the RenoPlex program.
Homes with sloped roofs
Make sure your outdoor gutters send rainwater to a permeable surface and that they are not connected to the foundation drain.
Plex buildings
Even if your valves were installed according to standards, it’s possible that there may only be one indoor pipe that combines rainwater from the flat roof and sanitary water, which is common to buildings built before the 1980s. This type of pipe presents a risk of water overflowing from plumbing fixtures onto floors during heavy rains, which creates autoflooding (i.e., rainwater from the roof pushing back into the building on upper floors).
Consult a building plumbing professional to find out what solutions are available to you. But first, see the recommendations of the Régie du bâtiment du Québec (in French). It is also important to check with your borough if special standards apply, or if a permit or authorization is required. Stormwater management is governed by a by-law.
Subsidy program
Do you have to carry out potentially expensive renovations to adapt your building? Montréal’s RenoPlex program offers a subsidy for certain types of renovation that help reduce the risk of flooding. Check the criteria and eligibility of your renovation project.
Available technical resources
Écohabitation Québec (in French), a partner of the city, evaluates solutions and materials to protect against flooding. You can access test results, pilot projects, webinars and reference lists to find specialized companies (plumbing, architecture, heritage).
Architectures sans frontières Québec (ASFQ) has produced a guide with technical data sheets for adapting homes or buildings to flooding that will help you determine the best options for your situation.
Vulnerability map
You can view the Montréal agglomeration climate risk vulnerability map (in French) and select the “Identification des cuvettes 2021” (2021 Basin Identification) map. This map identifies areas whose naturally sunken topography has the potential for surface water accumulation during heavy rains.
Tangible actions for a safer future
Montréal has set out 10 key measures to adapt to torrential rains in its action plan for flood resilience during heavy rains. One of the components of this plan includes support measures for owners to increase the resilience of their building. In particular, the city is committed to offering advisory services to owners on how to best protect their building against floods. In addition, Montréal is actively collaborating with a number of organizations and institutions to document and test various protection measures on private property, to ensure that they can effectively reduce the risk of flooding.
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