Bathroom Waterproof Paint Selection Guide
- WILLIAM KIM
- Aug 25
- 3 min read
Why bathroom paint is different
Bathrooms face constant moisture, steam, condensation, temperature swings, and chemical cleaners. Your coating system must resist water, mould, and scrubbing, while adhering to diverse substrates (gyprock, cement board, render, tiles).
1) Know your substrate (pick the right system)
New plaster/gyprock: Moisture-resistant sealer/primer → bathroom-rated acrylic topcoat (mould-resistant, low/zero-VOC if possible).
Cement sheet/render (wet walls, shower recess surrounds): Waterproofing membrane (if in wet zone per code) → compatible primer → acrylic or water-based enamel.
Previously painted walls: Clean/degloss → patch/sand → stain-blocking primer (for tannin/water marks) → bathroom acrylic.
Bare timber trims/doors: Stain-blocking primer (tannin) → water-based enamel (satin/semi-gloss).
Tiles (feature walls outside direct shower): Degrease → abrade (or adhesion primer) → tile-capable topcoat (confirm product spec). Inside the shower, tiling + membrane is superior to paint alone.
2) Paint types & when to use them
Bathroom-rated Acrylic (interior): Everyday walls/ceilings. Low odour, quick recoat, mould-resistant additives, good scrub resistance.
Water-based Enamel: Harder finish for doors, trims, window sills, splash-prone zones.
Two-part Epoxy (select areas): Exceptional water/chemical resistance; suited to vanities, benchtops, floors (non-slip version). Requires precise mixing/ventilation.
Elastomeric/Waterproofing Membrane: Under-tile or behind finishes in wet zones to stop water ingress; then overcoat per spec. (This is not your final wall paint—it's part of the system.)
3) Sheen level (function + look)
Ceilings: Flat/Matte (anti-mould) to hide defects, but ensure “bathroom” spec.
Walls: Satin (best balance of cleanability and appearance).
Trims/Doors: Semi-gloss (toughest, wipes clean easily).
4) Mould & moisture control (product + practice)
Choose paints labeled mould-resistant and bathroom/kitchen grade.
Improve ventilation (exhaust fan to exterior; 12–15 air changes/hour ideal).
Seal gaps/penetrations with sanitary silicone; re-silicone when brittle.
Keep humidity 40–60% RH where possible; squeegee tiles/shower glass.
5) Prep checklist (Do not skip)
Degrease (sugar soap) → rinse → dry.
Kill mould (bathroom mould wash), allow full dry.
Repair pinholes/gouges (filler), sand P180–240; vacuum dust.
Spot/stain-block water marks/tannin; prime glossy areas for adhesion.
Mask, protect, and ensure ventilation before painting.
6) Application basics
Temperature/RH: 10–30 °C; moderate humidity.
Coats: Typically 2 coats (plus primer where required).
Recoat time: 2–4 h for acrylic (check label); epoxy varies (pot life!).
Cure: Avoid hot showers for 48–72 h; full hardness may take 7 days.
Edges: Cut-in first; maintain a wet edge to avoid lap marks.
7) Common mistakes (and fixes)
Using standard interior paint → early mould/peeling.Fix: Switch to bathroom-rated paint; improve ventilation.
No membrane in wet zones → hidden leaks.Fix: Follow wet-area waterproofing steps before painting.
Painting over mould → stains return.Fix: Treat/kill mould, dry thoroughly, then prime/paint.
Matte on busy walls → burnishing/stains.Fix: Use Satin or Semi-gloss for wipeability.
Rushing recoat/cure → tacky finish, sheen patchiness.Fix: Respect label times; extend in cool/humid weather.
8) Quick selection table
Area | System | Sheen |
Ceiling (steam) | Anti-mould bathroom acrylic | Flat/Matte |
Walls (general) | Primer (as needed) → Bathroom acrylic | Satin |
Splash-prone walls | Adhesion/stain-block primer → Water-based enamel | Satin |
Trims/doors | Stain-blocking primer → Water-based enamel | Semi-gloss |
Shower recess (substrate) | Waterproofing membrane (+ tile finish) |
9) Maintenance tips
Run the exhaust during and 20–30 min after showers.
Wipe condensation; clean with non-abrasive cleaners.
Inspect silicone/caulk annually; renew before failure.
Re-coat high-wear areas every 3–5 years (usage dependent).
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