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Shower & Bathtub Waterproof Finish (NBC 9.29.2)

The National Building Code's waterproof-finish heights — 1.8 m in a shower stall, 1.2 m above a bathtub with a shower, 400 mm above one without — plus the tile backer rule.

NBC 2020 (provinces amend) Clause CA NBC 9.29.10

The requirement

A shower stall needs a waterproof finish up to at least 1.8 m above the floor. A tub with a shower over it needs 1.2 m above the rim. A tub with no shower needs 400 mm above the rim. That is NBC 2020, Division B, Article 9.29.2.1.

So the code does not set one height for the whole room. It sets three. The height depends on the fixture:

FixtureWaterproof finish required to
Shower stallAt least 1.8 m above the floor
Bathtub fitted with a showerAt least 1.2 m above the rim
Bathtub not fitted with a showerAt least 400 mm above the rim

The shower stall gets the tallest wall. It is the wettest spot in the room. A tub with no shower only gets splashed. So it only needs the low splash height.

12≥ 400 mm≥ 1.8 m
NBC 2020 · 9.29.2
  1. 1 shower floor
  2. 2 basin / bath

What counts as a waterproof finish, and what backs it

Article 9.29.2.2 lists the finishes that pass. They are ceramic, plastic or metal tile, sheet vinyl, tempered hardboard, laminated thermosetting decorative sheets, or linoleum. Plain painted drywall does not pass on its own.

Tiling? There is a backer rule too. Article 9.29.10.4 covers ceramic and plastic tile on walls around bathtubs or showers. That tile must go over moisture-resistant backing. Bare gypsum board is not enough.

There is a caulking rule at the tub as well. Article 9.29.10.5 covers the joint where the wall tile meets the bathtub. That joint must be caulked with a mildew-resistant sealing compound. The compound must conform to CAN/CGSB-19.22-M.

Note what these articles do not ask for. They do not call for a sheet or liquid membrane behind the backing. The code wording stops at “waterproof finish” and “moisture-resistant backing.” Membrane systems sit with the maker’s instructions and standards like the CSA A123 series. These clauses do not make a membrane a required layer.

On site — what to check

  1. Read the fixture, not just the room. A shower stall needs 1.8 m. A tub with a shower needs 1.2 m above the rim. A plain tub needs 400 mm above the rim.
  2. Pick a listed finish. Tile, sheet vinyl, tempered hardboard, laminated thermosetting sheet or linoleum. Take it up to the required height.
  3. Back the tile right. Moisture-resistant backing behind tile around any bathtub or shower. Not plain gypsum board.
  4. Caulk the tub-to-tile joint. Use a mildew-resistant sealant that meets CAN/CGSB-19.22-M.
  5. Check your province. Confirm the edition and any local amendments with your building department before you build.
  • Part of the Canada building codes hub. It shows how the NBC is adopted province by province.
  • Building the room around it? See Canada minimum ceiling heights. That page covers the 2.1 m rule for bathrooms and laundries.
  • Setting the shower floor slope and drain is a plumbing job. Check with your plumber and the locally adopted plumbing code.

Sources

  • NBC 2020, Division B, Section 9.29 “Interior Wall and Ceiling Finishes,” Article 9.29.2.1 “Waterproof Wall Finish — Where Required” and Article 9.29.2.2 “Materials” — the 1.8 m / 1.2 m / 400 mm heights and the listed waterproof-finish materials. Free official PDF via nrc-publications.canada.ca (National Building Code of Canada 2020, Volume 2). (Confirmed by direct text extraction from the official NRC PDF, verified 2026-07-31.)
  • NBC 2020, Article 9.29.10.4 “Moisture-Resistant Backing” and Article 9.29.10.5 “Joints between Tiles and Bathtub” — the tile-backer requirement and the CAN/CGSB-19.22-M caulking requirement at the tub-to-tile joint. Same source and verification as above. (Note: Article 9.29.10 itself is titled “Wall Tile Finish” and covers tile installation method — mortar base, adhesives, backing, joints. The waterproof height figures come from the separate Article 9.29.2, not 9.29.10.)
  • Adoption caveat: The National Building Code is a model code with no legal force of its own — it binds you only once your province or territory adopts it, often with amendments. Ontario runs the Ontario Building Code, Québec its own construction code, and British Columbia the BC Building Code, each with different numbering and, in places, different figures. Always confirm the edition in force where you build.

Related building rules

Frequently asked questions

How high does a shower wall have to be waterproofed in Canada?
Under the National Building Code, a shower stall needs a waterproof finish up to at least 1.8 m above the floor. The rule is NBC 2020, Article 9.29.2.1, in the interior finishes section.
What about the wall above a bathtub?
It depends on the tub. A bathtub fitted with a shower needs a waterproof finish at least 1.2 m above the rim. A bathtub with no shower needs 400 mm above the rim. The lower figure covers splashes only. It is not a full shower wall.
What materials count as a waterproof finish under the NBC?
Article 9.29.2.2 lists ceramic, plastic or metal tile, sheet vinyl, tempered hardboard, laminated thermosetting decorative sheets, or linoleum. Plain gypsum board on its own does not qualify.
Does tile need a special backer behind it?
Yes. NBC 2020 Article 9.29.10.4 says ceramic and plastic tile around bathtubs or showers must go over moisture-resistant backing, not plain gypsum board. The joint between the wall tile and the tub must also be caulked. The sealant must be mildew-resistant and meet CAN/CGSB-19.22-M (Article 9.29.10.5).
Do these NBC figures apply everywhere in Canada?
Not automatically. The NBC is a model code. It binds you only once your province or territory adopts it. Some publish their own code instead. Ontario runs the Ontario Building Code, Québec its own construction code, and British Columbia the BC Building Code. Confirm the edition in force where you build.