Can You Add a Rooftop Terrace on an Existing Flat Roof?

Transforming a flat roof into a rooftop terrace is a growing trend among homeowners in Montreal. This type of project not only makes better use of urban space but also adds significant value to a property and enhances the overall quality of life. Since 1924, René Perron Couvreurs has been supporting both residential and commercial clients with all types of roofing projects, including the construction of rooftop terraces on flat roofs across Montreal, Laval, the North Shore, and the South Shore.

Is it possible to add a terrace on an existing flat roof?

Yes, it is absolutely possible to add a terrace to an existing flat roof, but several necessary conditions must be met. First, it’s essential to distinguish between a roof that’s simply accessible and one that’s designed to support a terrace. A flat roof in Montreal must be able to bear the additional weight of furniture, people, and heavy winter snow. Before moving forward, a structural evaluation and roof inspection by qualified professionals is crucial to ensure the safety and long-term durability of the rooftop terrace.

What steps should you follow?

1. Structural inspection and analysis

   Before proceeding, the building must be inspected to determine whether it can safely support a rooftop terrace. This includes checking the load capacity and evaluating the current state of the roof and supporting structure.

2. Consultation with a structural engineer

   In Montreal, consulting with a structural engineer is often required to confirm the project’s feasibility and ensure compliance with building codes and safety standards.

3. Waterproofing membrane check

   The condition of the waterproof membrane is critical. It must either be in perfect condition or reinforced to prevent any risk of water infiltration under the terrace.

4. Terrace design planning

   Material selection (wood, steel, pavers), guardrail and staircase design, and accessibility considerations should all be thought through from the very beginning.

5. Permits and local regulations

   You must comply with municipal regulations and obtain the proper permits from the City of Montreal before beginning any construction work.

Regulations in Montreal and local considerations

Adding a rooftop terrace in Montreal is subject to strict building regulations. A permit from the city is mandatory, and safety standards must be met, including minimum guardrail height, maximum load control, and secure access. Requirements may vary depending on the area (urban, heritage zones, etc.) or municipality (Montreal, Laval, North Shore, South Shore). That’s why it’s essential to consult with professionals who understand local bylaws and construction rules.

What materials should you use for a rooftop terrace?

In the Montreal area, the most popular materials for rooftop terraces include:

• Treated wood or composite decking: Offers a warm, natural look, but requires proper maintenance.

• Interlocking tiles or pedestal pavers: Easy to install and remove; also help protect the waterproof membrane.

• Steel or aluminum: Strong and durable, ideal for railings and structural elements.

• Concrete slabs: Extremely durable, though heavier and requiring proper structural support.

Protecting the roof membrane beneath the terrace is crucial to prevent premature damage. All materials used must also be able to withstand Quebec’s harsh winters and dramatic temperature swings.

Adding a rooftop terrace to a flat roof in Montreal is both an attractive and achievable idea, as long as each step is followed carefully, and local building codes are adhered to. Before jumping into your project, have your roof inspected by experienced professionals to ensure your terrace is both safe and long-lasting.

Trust René Perron Couvreurs, experts serving Montreal, Laval, the North Shore, and the South Shore.

Book your inspection today and let our team guide you every step of the way!