National baseline
Start with Part 9 (housing and small buildings) provisions for below-grade moisture protection, drainage, and backfill requirements.
Canadian building code question
What are the building code requirements for damp-proofing and waterproofing in Canada?
The NBC requires damp-proofing on below-grade walls as a baseline, with full waterproofing required where hydrostatic pressure exists or where the space below grade is a habitable area. Requirements vary by soil conditions, water table, and provincial adoption.
Moisture protection for foundations and below-grade construction is a critical durability and habitability requirement. The code distinguishes between damp-proofing (moisture resistance) and waterproofing (hydrostatic pressure resistance), and the trigger for each depends on water table conditions, intended use of the below-grade space, and soil drainage. Getting this wrong leads to mould, structural deterioration, and warranty claims.
What to check first
- Damp-proofing is the baseline requirement for most below-grade walls; waterproofing is required when hydrostatic pressure is present or the space is habitable.
- Drainage layer, granular backfill, and weeping tile requirements work together with the moisture barrier to protect the foundation.
- Provincial amendments and local soil conditions can change whether damp-proofing or waterproofing is required.
Jurisdiction notes
Province and edition check
Some provinces add requirements for specific soil types, water table conditions, or energy code interactions with below-grade insulation and moisture barriers.
Project-specific variables
Water table depth, soil permeability, intended use of below-grade space, and insulation placement all affect whether damp-proofing or waterproofing applies.
Work through it in this order
- Determine whether the below-grade space is habitable or unfinished, and whether hydrostatic pressure is expected.
- Identify the NBC provisions for damp-proofing and waterproofing that apply to the foundation type.
- Verify drainage requirements including weeping tile, granular backfill, and drainage membranes.
- Check provincial adoption for any amendments related to soil conditions or energy code interactions.
Common questions
When is waterproofing required instead of damp-proofing?
Waterproofing is typically required when the below-grade space is habitable or when hydrostatic pressure from a high water table is expected. Verify the triggering conditions in the applicable code edition.
Does the code require a drainage membrane on all foundations?
Not always. The requirement depends on the foundation type, soil conditions, and whether damp-proofing or waterproofing is required. Check the specific provisions for your project.
Are there different requirements for slab-on-grade vs basement walls?
Yes. Slab-on-grade moisture protection requirements differ from below-grade wall requirements. Each has specific provisions for vapour barriers, drainage, and moisture resistance.