Moisture in the Basement

Basement moisture is problematic for several reasons including health concerns, structural damage, and potential flooding. A damp basement is caused by excess moisture from humidity building up inside the home or from water entering in from the outside. Here are some ways to keep moisture out of the basement.

Inside or Outside?

In order to keep moisture out, you must first know where it’s coming from. Follow these steps to conduct the simple foil test:

  • start with a dry patch of basement wall – use a safe portable heater if needed
  • tape a piece of aluminum foil to the wall – tape should be attached on all four sides
  • leave the foil on the wall for at least 48 hours
  • remove the aluminum foil

If the foil side facing you is wet, condensation is building up in the basement. But if removing the foil reveals a wet patch of wall, then the water is entering from the outside.

Inside the House

Indoor humidity occurs when warm air condenses on cold surfaces. Ways to get rid of excess humidity in the basement include:

  • insulate pipes
  • insulate walls or replace old/outdated insulation
  • fix air vent leaks
  • fix water tap and pipe leaks; replace aging pipes
  • move the air around after showering/bathing in a basement bathroom – open a window if you can’t install a fan
  • install a dryer vent if you don’t already have one
  • discontinue using a humidifier
  • use an energy-efficient dehumidifier

Outside the House

When water enters the basement from the outside, the typical cause is drainage-related issues. Some signs that poor drainage is the reason for a damp basement are:

  • pooling water around downspouts
  • displaced soil or washed out patches of landscaping
  • overflowing gutters
  • mould, moss, or mildew growth on siding
  • holes or cracks in the foundation
  • downspouts are not long enough, depositing water too close to the foundation

To prevent water entering the basement from the outside:

  • check downspouts for blockages and remove any clogs
  • add more soil or mulch around the foundation so water is absorbed
  • clean the gutters regularly and keep them maintained
  • remove mould/moss/mildew from siding – especially moss as it absorbs and retains moisture
  • repair holes or cracks by waterproofing the foundation
  • add downspout extenders or splash blocks to your gutter system