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title: "Waterproofing in Canadian Construction | AVANORTH"
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**Construction Tips**·January 9, 2026· 4 min read
# **The Importance of Waterproofing in Canadian Construction**
Water is the number one enemy of buildings. Proper waterproofing during construction prevents costly damage and protects the structure for decades.
**AVANORTH Team**
AVANORTH Construction
## Water: The Silent Destroyer
If you ask experienced builders what causes the most damage to buildings over time, the answer is almost always water. Not fire, not wind, not earthquakes. Water, in all its forms, is the relentless force that degrades concrete, corrodes steel, rots wood, grows mould, and destroys finishes. In Canada, where buildings face rain, snow, ice, and freeze-thaw cycles throughout the year, waterproofing is not optional. It is essential.
## Types of Waterproofing in Construction
Waterproofing is applied at multiple points in a building's construction:
- **Below-grade waterproofing:** Foundation walls and slabs that are in contact with soil and groundwater need continuous waterproofing membranes. This is the most critical application because below-grade repairs are extremely expensive and disruptive.
- **Above-grade weather barriers:** The building envelope, including walls, windows, and roofing, must prevent bulk water and wind-driven rain from entering the structure.
- **Wet area waterproofing:** Bathrooms, kitchens, laundry rooms, and mechanical rooms need waterproofing at floor and wall surfaces to prevent moisture migration into structural elements.
- **Deck and balcony waterproofing:** Exposed horizontal surfaces are particularly vulnerable because they collect water and are subject to freeze-thaw cycles.
## Below-Grade Waterproofing Methods
For foundation walls, the following systems are commonly used in Ontario:
- **Dampproofing (not true waterproofing):** A spray-applied asphalt emulsion that resists moisture but does not bridge cracks or withstand hydrostatic pressure. Only suitable where groundwater is not expected to contact the wall.
- **Sheet membrane systems:** Self-adhering rubberized asphalt membranes that bond directly to the concrete wall. These bridge minor cracks and provide continuous waterproofing. Brands like Blueskin and Grace Ice and Water Shield are common.
- **Fluid-applied membranes:** Spray or roller-applied liquid membranes that cure into a continuous rubber-like coating. They conform to irregular surfaces and are seamless.
- **Bentonite clay systems:** Panels or sheets containing sodium bentonite clay that swells when wet, creating a self-sealing waterproof barrier. Useful in applications where the membrane must be applied before concrete is poured (blindside waterproofing).
- **Drainage board:** While not waterproofing itself, drainage board (dimple board) is installed over the waterproofing membrane to channel water down to the footing drain and protect the membrane from backfill damage.
## The Critical Role of Footing Drains
Even the best waterproofing membrane needs help. Footing drains (also called weeping tile) are perforated pipes installed at the base of the foundation to collect and redirect groundwater away from the building. In Ontario, footing drains are required by the building code for all below-grade occupied spaces.
Common footing drain configurations include:
- Interior footing drain connected to a sump pump (most common in residential)
- Exterior footing drain connected to storm sewer or daylight (gravity discharge)
- Both interior and exterior drains for maximum protection
## Above-Grade Waterproofing
The building envelope must manage water through a system of barriers:
- **Weather-resistive barrier (WRB):** A membrane applied over the exterior sheathing that prevents bulk water from reaching the structure while allowing vapour to escape. Tyvek and Typar are common examples.
- **Flashing:** Metal or membrane flashing at all horizontal transitions (window sills, shelf angles, roof-to-wall junctions) directs water outward.
- **Caulking and sealants:** Joints between dissimilar materials must be sealed with appropriate sealants that accommodate thermal movement.
- **Proper grading:** The ground surface should slope away from the building at a minimum 5 per cent grade for the first 2 metres.
## Cost of Getting It Wrong
The cost of waterproofing during construction is a fraction of the cost of remediation after the fact. Foundation waterproofing for a typical residential project costs 5,000 to 15,000 dollars. Repairing foundation water damage after the building is occupied can easily exceed 50,000 to 100,000 dollars, not including the disruption and potential health impacts from mould growth.
At AVANORTH, waterproofing is a core competency. We specify and install waterproofing systems that protect every building we construct because water damage is entirely preventable when the right materials and methods are used from the start.
#waterproofing #foundation #protection
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