5 Signs Your Crawlspace Has a Moisture Problem

Up to 50% of the air you breathe on your first floor originates in your crawlspace, pulled up through the floor by stack effect. If your crawlspace is damp and moldy, that air — and that smell — enters your living space. A persistent musty odor, especially on the ground floor or in basement-adjacent rooms, is the most common sign of crawlspace moisture.

Air fresheners and ventilation don't fix it because the source is below. The only lasting fix is to dry and seal the crawlspace so the air rising into your home is clean and dry.

A damp, uninsulated crawlspace lets cold air sit against the underside of your floor, making the floors above noticeably cold in winter. If your feet are freezing on hardwood or tile above a crawlspace, the crawlspace is likely the culprit. Encapsulation and insulation warm the floor and reduce heating bills.

Look in your crawlspace for dark spots on the wood joists, a fuzzy or slimy coating on surfaces, or soft, spongy wood. Mold grows when humidity stays above 60% — and an unsealed crawlspace in Ottawa's humid climate easily exceeds that. Wood rot (soft, crumbling wood) means moisture has been present long enough to damage the structure. Both require immediate attention.

After rain or in spring, check your crawlspace floor. Puddles, dark damp soil, or water staining on the walls means water is entering — through the foundation, from poor grading, or down through vents. Even without standing water, a consistently damp dirt floor releases gallons of water vapor into the air daily. A vapor barrier and proper drainage stop it.

If your home feels humid even with the AC running, or you see condensation on windows and cold pipes, your crawlspace may be the source. A damp crawlspace continuously adds moisture to the air in your home, forcing your dehumidifier or AC to work harder. Sealing the crawlspace removes that moisture load and lowers your energy bills.