Checklist: Moisture Problems in Exterior Walls
Moisture in exterior walls can come from exterior and interior sources.
Typical Signs
- Condensation on walls.
- Bulging, buckled or rotting siding.
- Blistering or flaking paint.
- Appearance of frost condensation.
- Wet stains or chalky deposits on brick or stucco.
- Moisture-damaged window and door frames.
- Moisture damaged drywall and flooring inside house next to exterior walls.
- Damp or wet flooring at base of walls.
Possible Causes
- Warm, moist, inside air leaking into exterior walls where the moisture can condense and wet surrounding materials.
- Wind-driven rain causing water to penetrate the wall cladding from outside.
- Inadequate or missing flashings around windows, doors, joints, etc.
- Overflow of rain barrel not properly drained.
- Broken downspout or downspout termination on foundation.
- No eavestroughs or gutters.
- Broken, clogged or poorly sloped eavestrough/gutter.
- Backsplash of rain from hard ground surfaces back onto walls.
- Siding installed too close to ground with less than 200 mm (8in.) of clearance.
- Poor drainage from porches and decks.
- Outdoor tap/garden hose leaking against wall.
- Little or no wall insulation causing condensation to occur.
Practical Solutions
- Inside the home, seal all openings into outer walls that would allow air leakage.
- Reduce excess moisture in the house.
- Improve house ventilation.
- Install or repair flashing to lead rain away from wall.
- Direct overflow spout of rain barrel away from walls and foundation.
- Repair broken downspouts.
- Install and properly slope eavestroughs/ gutters and extend away from the house.
- Repair or clean out eavestroughs/ gutters to prevent overflows.
- Re-grade ground to drain surface water away from building.
- Fix leaky tap. Add hose extension to minimize water pooling under foundation.
- Provide adequate clearance between siding and ground and decks, patios.
- Caulk and seal exterior joints around windows, doors, joints in siding, flashing, balcony framing.
- Ensure walls are well insulated and air sealed.
