Canada · Roofs & rooftops

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

National baseline

Start with Part 9 (housing and small buildings) provisions for below-grade moisture protection, drainage, and backfill requirements.

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.

Not professional advice

CodeCan reports what the published building code says. It is not legal, engineering, or architectural advice, and it does not certify compliance. Building codes are adopted and amended provincially and enforced locally — always verify with your authority having jurisdiction (AHJ) before you build.

Work through it in this order

  1. Determine whether the below-grade space is habitable or unfinished, and whether hydrostatic pressure is expected.
  2. Identify the NBC provisions for damp-proofing and waterproofing that apply to the foundation type.
  3. Verify drainage requirements including weeping tile, granular backfill, and drainage membranes.
  4. 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.