The most expensive basement mistake is finishing over a moisture problem. Drywall, insulation and carpet trap damp against the foundation, and the result is mould, smells and a basement that has to be torn out again.
Signs to look for
- Water stains or tide lines on the walls or floor
- White, chalky deposits (efflorescence) on concrete, a sign that water has moved through it
- A musty smell, especially in summer
- Damp spots after heavy rain or snowmelt
- Peeling paint on foundation walls
- Cracks in the foundation walls or floor that let water in
A simple test
Tape a square of plastic sheet tightly to the wall or floor and leave it for a couple of days. If there's moisture on the side touching the concrete, water is coming through. If it's on the room side, the air is humid. Both can be dealt with, but the fix is different.
Common fixes
- Outside first. Downspouts that drain away from the house and soil that slopes away from the foundation solve many problems.
- Crack repair for foundation cracks that let water in.
- A dehumidifier for humid air, especially in summer.
- Sump pump and drainage for wetter sites.
- Proper wall assemblies. How the walls are insulated and sealed makes a big difference to how a finished basement handles moisture.
Older and rural homes
Older homes around Oxford County, especially those with stone or block foundations, and homes near rivers like the Thames and the Nith, are worth a closer look. Stone foundations, like some in St. Marys, need to be finished in a way that still lets the walls dry.
Get it checked as part of the job
A good contractor looks for moisture before they quote, and tells you what needs to be fixed before finishing. See basement finishing, or send the form at the top of this page.