Balcony Waterproofing & EMTC Requirements

Waterproofing – The New 2025 EMTC Standard

On July 9, 2025, the province of Quebec introduced a new construction code requirement for balconies built with Encapsulated Mass Timber Components (EMTC). This update was part of a broader safety and durability initiative aimed at extending the lifespan of exterior structures and preventing costly, preventable damage.

The Rule: All EMTC balconies must now be covered with a certified waterproof membrane that meets provincial and manufacturer performance standards. This regulation applies to:

Newly built EMTC balconies.
Existing EMTC balconies are undergoing major repairs or surface replacement.
Balconies where any structural components are exposed during renovations.

What is EMTC?

Encapsulated Mass Timber Components are engineered wood structures (like cross-laminated timber or glulam beams) that are encased in a protective coating or layer to resist environmental exposure. While EMTC offers strength, sustainability, and lightweight construction advantages, its performance depends heavily on keeping moisture out. Without proper protection, wood-based components can absorb water, leading to rot, mold, swelling, and structural failure.

Purpose of the New Waterproofing Standard

Quebec’s climate is one of the most challenging in North America for exterior structures. The new standard addresses:

Water Infiltration Prevention
- Moisture penetration is the leading cause of structural degradation in timber-based balconies.
- Once water enters, freeze–thaw cycles can expand cracks and accelerate damage.
Structural Integrity Preservation
- EMTC relies on adhesive bonds and laminated layers. Prolonged moisture exposure weakens these bonds, compromising load capacity and safety.
Extended Lifespan
- With a properly installed waterproof membrane, the service life of EMTC balconies can be extended by decades.
Cost Reduction Over Time
- Waterproofing is far less expensive than replacing compromised beams or entire balcony structures.

Certified Waterproof Membranes – What’s Required

The regulation calls for membranes that:

Meet manufacturer specifications for exterior horizontal surfaces.
Resist freeze–thaw cycles without cracking or delaminating.
Are UV-stable to prevent degradation from sunlight.
Provide chemical resistance against de-icing salts and pollutants.
Have a minimum proven service life under similar climate conditions.

Installation Best Practices

To meet the 2025 standard, professional installation must follow strict procedures:

Surface Preparation – Diamond grinding, scarification, or shot blasting to achieve the correct surface profile (CSP3–CSP5).
Moisture Testing – Ensure substrate is within manufacturer’s allowable moisture range before applying membrane.
Primer Application – Use compatible primers for optimal bonding.
Membrane Layering – Apply multiple coats to achieve required thickness and performance rating.
Detail Work – Special attention to edges, railing posts, drains, and seams to eliminate leak points.
Curing & Inspection – Allow adequate curing time, then conduct adhesion and thickness testing before returning balcony to service.

Consequences of Skipping Waterproofing

Ignoring this regulation can lead to:

Accelerated structural failure of the balcony.
Insurance claim denials for water-related damage.
Non-compliance fines from municipal or RBQ inspections.
Costly emergency repairs and liability risks if failure causes injury.

Tip for Property Owners: Even if your balcony is not EMTC, applying a certified waterproof membrane is one of the best long-term investments you can make in its durability and safety.