Moisture and mold in BC homes

Coastal British Columbia combines long rainy seasons with mild temperatures. That is a gift for gardens and a problem for houses. Wood, drywall, and insulation stay in the humidity range where mold can colonize, especially in rooms that are closed up for winter heating.

What you are usually seeing

Window condensation on cold mornings is common and not automatically a crisis. Persistent wet sills, peeling paint on exterior walls, black spotting on bathroom caulk, and a musty smell that returns after you air the house out are more serious. A smell that lives in one room often points to a hidden wet assembly: an unvented bath fan, a leaky window, or a damp crawl space feeding the floor above.

Distinguish condensation from leaks. Condensation shows up on the coldest surfaces — windows, uninsulated corners, closets on exterior walls. Leaks follow gravity and weather: stains after storms, wet carpet at a wall, or drips under a plumbing run.

Control the source, then the air

Dehumidifiers help, especially in basements and crawl spaces, but they do not replace fixing a gutter that dumps water against the foundation. The sequence that actually works:

1. Stop liquid water (roof, flashing, grading, plumbing).
2. Stop humid air from wet voids (crawl space, attic bath-fan dumps).
3. Give occupied rooms a path out (bath fans, range hood, HRV/ERV).
4. Then dry leftover humidity with a dehumidifier sized for the space.

When to stop DIY

Small surface spots on hard, non-porous materials can often be cleaned with care and better ventilation afterward. Widespread growth, mold in HVAC, wet drywall larger than a dinner plate, or anyone in the home with asthma or immune issues is a reason to bring in a qualified inspector or remediator. In BC, hidden growth behind walls after leaks is common in older assemblies — poking one hole is not a full assessment.