TSA Technical Series: Updating Toronto’s Foundation Drainage Policy

Increased storms and flooding have drawn greater attention to the city’s stormwater management, especially the combined sewer system which carries both domestic waste and urban runoff. In effect since 2022, the City of Toronto’s Foundation Drainage Policy (FDP) aimed to preserve this limited infrastructure by prohibiting any groundwater discharge from new developments into the system. While well-intended, the policy has had significant side effects, forcing many sites to use costly, watertight “bathtubbed” foundations and adding millions in costs to project budgets—including for much needed housing. After significant industry advocacy, a series of amendments is coming into effect on October 1, 2026, which aim to strike a balance between protecting the city’s sewer capacity and reducing unnecessary construction barriers.

Join us for a lecture with Michael Diez de Aux—Principal at Grounded Engineering and one of the advocates behind these amendments—as we examine the FDP, its impact on development, and the updated requirements. The lecture will also review key recommendations to enable drained basements while preserving our city’s sewer capacity.  

By attending this webinar, participants will:

• Gain perspective on the 2022 Foundation Drainage Policy, its origins, and rationale.
• Review lessons learned over the past 3 years, including unintended impacts on housing delivery with a specific focus on mid-rise, affordable and non-profit housing.
• Understand five key changes recommended to once again enable drained basements. 
• Review the updated FDP coming into effect October 2026.

Additional Resources

• City of Toronto Foundation Drainage Policy
• 2026 Amendments to Foundation Drainage Policy
• UrbanToronto Article: Low-Flow Basements Could Cut Costs, Restart Some Stalled Housing Projects.

Above photo courtesy of Grounded Engineering.

TSA MEMBERS: This event is free for TSA Members using the discount code found in the TSA Bulletin and on your Member Dashboard. Not a member yet? Membership is open to everyone and you can join here (student memberships are free!).

OAA MEMBERS:  This lecture is eligible for 1 OAA Structured Learning Hours. When registering, please include your full name as registered with the OAA to ensure your certificate of participation is credited properly. Please also include an email address you check frequently to ensure you receive our certificate in a timely manner.