New Flood-proofing Measures: Greater Protection for Buildings in Saint-Laurent

Published June 25, 2025 - 8:30 am

At a special meeting held on June 13, Saint-Laurent adopted bylaw amendments to allow residents to make their properties more resilient to the risks of urban flooding during heavy rainfalls.

Rapidly worsening climate change

Heavy rainfalls in the summer of 2024 caused significant flooding in certain sectors of Saint-Laurent, reminding us that climate change is increasing the frequency and intensity of this type of problem.

Bylaw amendments

In response to the extent of these extreme weather events, and despite the numerous measures implemented by Saint-Laurent over the past forty years or so to limit the risks of flooding (retention basins, sponge parks, bio-retention areas, greening, resilient and draining street landscaping), Saint-Laurent has decided to go one step further by adopting bylaw RCA08-08-0001-175..

This bylaw, which amends bylaw CA08-08-0001, allows property owners to adapt the existing built environment in order to better protect their property and the people who live there. It also optimizes the design of new buildings so as to limit the risks of water infiltration.

Concrete and more lenient measures

These new provisions, applicable throughout the territory, mainly concern parking lot layout and the conditions for authorizing basement dwellings. 

Backfilling of downward-sloping driveways

From now on, owners of existing residential buildings with fewer than five housing units will be able to backfill their downward-sloping driveways and, under certain conditions, create new, compliant outdoor parking spaces.

Underground parking 

From now on, downward-sloping access to underground indoor parking facilities in new constructions will have to be provided within the building itself, except for two-family (h2) and multiplex (h3) buildings.

Driveways

All new driveways will have to be designed to prevent rainwater from the street from flowing onto private property. A small mound or a slope towards the street will therefore be required for all vehicle accessways.

Basement housing

Saint-Laurent has a large supply of basement housing. Given the current housing crisis, Saint-Laurent’s Administration is confirming that this option will be maintained and it is even allowing the creation of new basement dwellings, provided that flooding risks are reduced to a minimum by various devices such as watertight doors or other water barriers.

However, basement activities are limited for the following uses where the clientele is more vulnerable: schools, daycare centres, CHSLDs, etc.

Coordinated actions

These new measures adopted by Saint-Laurent are in line with the following action plans adopted by Montréal or the borough:

Workshops for the general public

Saint-Laurent will soon be offering a series of workshops designed to equip its residents with the measures they need to take in order to increase the resilience of their property in the face of the growing risks of urban flooding. The workshops will be offered in collaboration with Écohabitation and Ville de Montréal’s Service de l’eau.