Parking Lots and Industrial Roofs: Your Obligations Under Montreal’s Bylaw 20-030

The Problem: Surfaces That Prevent Water Infiltration

Commercial parking lot paving, warehouse flat roofs, industrial building roofs, concrete loading areas — all these impermeable surfaces share one thing in common: they prevent rainwater from naturally infiltrating into the soil.

The result: runoff accumulates, overloads municipal sewer systems, and contributes to urban flooding and backups. It is precisely to address this challenge that the City of Montreal adopted Bylaw 20-030.

Bylaw 20-030: Who Is Affected?

Bylaw 20-030 on connections to public water and sewer systems and stormwater management requires authorization from the Water Management Regulation Section (SRGE) when:

• After construction, your property includes more than 1,000 m² of impermeable surfaces

Key point: The 1,000 m² calculation accounts for a combination of all impermeable surfaces on the property — new, expanded, and existing. A 800 m² parking lot combined with a 300 m² roof already exceeds the threshold.

Case 1: Commercial and Institutional Parking Lots

A shopping center, grocery store, clinic, or office building parking lot often exceeds 1,000 m² of asphalt. During new construction, expansion, or major renovation, Bylaw 20-030 applies. Stormwater management solutions must be integrated from the design phase: bioretention islands between parking rows, vegetated swales along the perimeter, permeable pavers for pedestrian walkways.

Case 2: Industrial and Commercial Building Roofs

Warehouses, factories, and commercial buildings with flat roofs represent considerable impermeable surfaces. Combined with loading areas and employee parking, they frequently exceed the regulatory threshold. Options include underground or surface retention basins, draining roofs, and landscaping designed to capture and infiltrate runoff

Consequences of an Incomplete Application

The SRGE verifies the compliance of each project. Any incomplete or non-compliant application extends authorization delays and generates additional costs for the property owner. According to Article 122, you have 60 days to correct a non-compliant application, after which it may be rejected.

Additionally, within 60 days following completion of stormwater management system construction work, “as-built” final plans must be submitted to the SRGE.

Avizo’s Expertise in Stormwater Management

Our engineering team has developed specific expertise in stormwater management for large impermeable surfaces. We design solutions adapted to the real constraints of these projects: heavy vehicle traffic, limited space, snow removal requirements, integration with existing developments.

Our solutions:

• Rooftop retention — applicable to new construction
• Bioretention islands — integrated into parking lot islands to capture, filter, and infiltrate runoff
• Vegetated swales — along paved areas to naturally slow and treat water
• Retention basins — underground or surface, adapted to large industrial sites
• Draining roofs and permeable surfaces — to reduce runoff directly at the source

Our services:

✓ Stormwater management master plan — comprehensive planning required for multi-phase projects or institutional buildings
✓ Hydraulic and hydrological study and modeling — calculation of runoff flows generated by your parking lot or industrial roof
✓ Design of plans and specifications — retention structures sized for your site and integrated into your developments
✓ SRGE application preparation — complete and compliant application to avoid delays and rejections

Take Action

Whether you are the owner of a commercial parking lot, an industrial warehouse, or a developer of a new project, our engineering team is ready to support you. We transform your regulatory obligations into green, sustainable, and high-performing developments.