Painting Basement Suites and Bathrooms in Vancouver: Moisture, Mould and the Right Paint

Damp winters, cool basements and busy bathrooms are a tough combination. In many Metro Vancouver homes, the basement suite and the bathrooms are where paint takes the most punishment: steam from showers, condensation on cold walls and windows, and the dark spots that show up on ceilings and around tubs. The right paint helps, but it is only one part of the fix. Here is how we approach painting basement suites and bathrooms so the finish looks good and lasts.

Key takeaways

• Paint cannot fix a moisture problem. Health Canada says painting over mould does not kill it or stop it from growing back.
• Control moisture first: working exhaust fans vented outdoors, and indoor relative humidity between 30% and 50%.
• Choose a scrubbable, moisture-resistant finish made for bathrooms and other damp rooms, applied over clean, dry, properly primed surfaces.
• If mould is under the paint, the drywall needs to be removed and replaced, not painted.

Why basements and bathrooms struggle in Vancouver

Health Canada's guide to addressing moisture and mould indoors lists the usual sources of indoor moisture: showering, laundry and cooking, especially when exhaust fans are not working or not vented outside; water coming in through cracks or leaks in foundations, walls and windows; plumbing leaks; condensation on cold surfaces such as windows; and inadequate ventilation.

Basement suites often have several of these at once. They sit partly below grade, walls and windows can be cool, and a busy household may be cooking, showering and drying laundry in a small space. Long stretches of rainy weather do not help.

Step one: fix the moisture before you paint

Health Canada is clear that unless the cause of a moisture problem has been identified and solved, mould will come back. Before we paint a damp room, we look for the source and recommend that it be fixed first. Health Canada's checklist includes:

• Bathroom fans. Install an exhaust fan in each bathroom, make sure it vents outside and not into the attic, and keep it running for at least 30 minutes after a shower or bath.
• Humidity. Keep indoor relative humidity between 30% and 50%, and run a dehumidifier in damp areas such as basements if needed.
• Tub and shower surrounds. Repair cracked or damaged tiles, grout and caulking.
• Leaks. Repair plumbing leaks promptly.
• Outside drainage. Slope the ground away from the house and keep eavestroughs and downspouts clear and draining away from the foundation.
• Kitchen and laundry. Use the range hood when cooking and make sure the clothes dryer vents outside.

An inexpensive hygrometer can tell you what the humidity in your suite actually is. If it is regularly above 50%, deal with that before you repaint.

Step two: deal with existing mould safely

Health Canada's guide classifies mould by area. A small area is three or fewer patches with a total of one square metre or less, and it can usually be cleaned up by a homeowner with proper precautions. Larger areas, mould that keeps coming back and suspected hidden mould inside walls call for a qualified professional.

For small areas on painted walls, Health Canada recommends cleaning with a damp cloth and baking soda or a small amount of unscented soap, without getting the drywall too wet. In bathrooms, it suggests scrubbing visible mould with unscented dishwashing detergent and water. Health Canada also advises not to use bleach to clean up mould, and to wear safety glasses, an N95 respirator and gloves while cleaning.

Most importantly, Health Canada says painting over a mouldy surface does not kill mould and does not stop it from growing back. If mould is underneath the paint, the drywall will need to be removed and replaced. A good painting crew will tell you when a wall needs repair rather than another coat.

Step three: choose the right products

Paint for bathrooms and damp rooms

Most major brands make paints labelled for bathrooms, kitchens or high-humidity rooms. They are typically designed to resist moisture and mildew on the paint film and to stand up to scrubbing. Look for:

• A product made for high-humidity rooms, with mildew resistance stated on the label or data sheet
• A scrubbable finish, often satin or semi-gloss, so you can wipe off condensation and soap splashes
• Compatibility with the primer and existing paint, especially over old oil-based coatings

Remember that a mildew-resistant label describes how the paint film behaves. It does not stop mould growing behind the paint or on other surfaces in a damp room.

Primers

Stains from old water damage or smoke can bleed through new paint. A stain-blocking primer helps, but only once the leak is fixed and the area is dry. Bare drywall patches need primer too, or they can show through the finish coat.

Low-VOC options

Basement suites and bathrooms are small, closed spaces. In Canada, the federal Volatile Organic Compound (VOC) Concentration Limits for Architectural Coatings Regulations set limits on VOC content for paints and other architectural coatings. Many brands also sell low- or zero-VOC lines. Whatever product you choose, ventilate well during and after painting.

Step four: prep and application

1. Clean and dry. Wash walls and ceilings to remove soap film, grease and any small mould spots, then let them dry completely.
2. Repair. Replace water-damaged drywall, patch holes and sand smooth.
3. Caulk. Renew failed caulking around tubs, showers, sinks and trim with a product made for wet areas.
4. Prime. Spot-prime repairs and stains, or prime the whole surface where needed.
5. Paint. Apply the finish coats, following the manufacturer's directions for drying time.
6. Let it cure. Avoid hot showers and heavy steam for the time the manufacturer recommends, and run the fan.

Painting a rental suite

If you rent out your basement suite, painting between tenants is the easiest time to do it. If a tenant is living there, give proper notice before entering and plan the work around their schedule. Health Canada also notes that tenants who notice moisture or mould should tell the property owner, so a tenant report is a good reason to look into the cause, not just repaint.

Frequently asked questions

Will mildew-resistant paint stop mould?

It can help keep mildew off the paint surface, but it will not stop mould if moisture is not controlled. Fix the moisture source first.

Can I just paint over mould?

No. Health Canada says painting over mould does not kill it or stop it from growing back. Clean small areas properly, and replace drywall if mould is underneath the paint.

What sheen is best for a bathroom?

Satin or semi-gloss finishes are popular because they are easy to wipe clean. Many bathroom-specific paints come in a range of sheens, so check the label.

Do I need a professional for mould?

Health Canada recommends a qualified professional for large areas of mould, mould that keeps returning, or suspected hidden mould inside walls or ceilings.

Ready to get started?

If your bathroom or basement suite needs a fresh, durable finish, we can help you plan the prep and choose the right products. Get your free painting quote from 1-800 PRO PAINTER.

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