Crawl space mould: signs, causes and what to do
Short answer: Crawl space mould usually comes from moisture rising out of the soil, a damaged or missing vapour barrier, poor ventilation or plumbing leaks. Signs include a musty smell on the main floor, white or dark growth on joists and subfloor, condensation and standing water. The fix is to test, remove the growth under containment, and control the moisture.
Signs to look for
- A musty smell in the rooms above, often worse on damp days
- White, grey or black growth on joists, beams or the underside of the subfloor
- A torn, missing or wet vapour barrier, or exposed soil
- Standing water, efflorescence (white mineral deposits) on the foundation, or rust on metal
Why it is common in the Lower Mainland
Wet winters, high water tables in the Fraser delta and valley floor, and many older homes with crawl spaces mean that soil moisture moves into the crawl space and can feed mould on the wood framing.
What to do
Have it tested, and check homes built before 1990 for asbestos before disturbing materials. The growth is removed or cleaned under containment, and the source is fixed: vapour barrier, drainage, ventilation or leaks. See basement & crawlspace mould.
Frequently asked questions
Can crawl space mould affect the air in my house?
Yes. Air moves up from the crawl space into the living space, so odours and spores can enter the home.
Is a vapour barrier enough to stop crawl space mould?
It helps a lot, but drainage, ventilation and leak repair also matter. Existing growth still needs to be removed.
Should I clean crawl space mould myself?
We do not recommend it. The space is confined, there may be asbestos in older homes, and cleaning can spread spores without containment.
Need help? We serve the Lower Mainland, Fraser Valley and beyond. Call 604-619-6655.