Controlling Moisture in Your Basement

Moisture that hangs around in your basement is never a good thing. Damp air in a dark space provides the perfect conditions for mold growth or rodent nesting. Unaddressed moisture issues can also cause musty odours, perpetually damp air, or a ring of dampness at the base of cement walls. Unlike basement flooding, moisture buildup and the problems that result tend to occur over a longer period of time. After identifying the source, there are some hands-on solutions for controlling moisture in your basement.


When they see beads of water clinging to basement walls, homeowners might think that the water is coming in from the outside. But walls that look like they’re “sweating” are common when the basement is unfinished. Condensation typically occurs when warm air comes into direct contact with the cooler concrete walls. Ways to prevent or control basement condensation are:

  • Keep the temperature of the basement warm enough to prevent condensation from forming
  • Finish the basement – putting up walls creates a barrier between the air in the room and the concrete surfaces of the foundation
  • Part of the HVAC system, install a whole-house dehumidifier – if that is not an option, use a portable dehumidifier in the basement

Basement Plumbing Leaks

Do you have a laundry room, bathroom, or a built-in bar with a sink? Even if the leak is so small it’s not really noticeable, it will still release enough moisture into the air to become problematic over time. To protect against basement plumbing leaks:

  • Inspect water pipes and drain pipes every three or four months
  • Ensure shut-off valves are working
  • Check for “sponginess” by pressing firmly on the bottom of the shower stall walls

Sump Pump Basin

A sump pump provides protection against rainwater and groundwater from entering the basement. However, an open sump pump basin can encourage moisture accumulation and the constant release of that moisture into the air. The easiest solution to seal the water inside is to get a type of lid that screws down to the basin. When the basin is made of metal or clay, see if the lid can be screwed directly into the basement floor.

Dryer Vent

Does your dryer have a vent? It is the pipe attached to the back of the machine designed to take the heat and moisture from inside the dryer to the outside. If the pipe has become detached, the moist, heated air gets blown into the basement. Reconnect the pipe as soon as you have discovered that it’s been disconnected. Especially if it’s a gas dryer, it’s dangerous to operate the dryer without being it connected to the vent.


Water can get into the basement by seeping through cracks in the foundation. Runoff might also be able to enter through small gaps around windows and cracks in the trim around entry doors. Water pooling beneath downspouts or overflowing gutters sending water down damaged or worn siding panels will allow runoff to go where it doesn’t belong. Solutions to deal with seepage include:

  • Regularly maintain the gutter system – clean the gutters and downspouts to prevent debris buildup that causes clogs
  • Ensure downspouts are at least five feet away from the foundation and the soil is graded away from the house
  • Repair cracks in the foundation – when cracks have become too large consult with a licensed contractor
  • Repair broken window panes; recaulk window trim; fill in gaps around entry doors

Crawl Space

If a home doesn’t have a basement or it isn’t built on a slab it will typically have a crawl space. The main purpose of the crawl space is to allow air to circulate throughout the home. It also provides access to necessary systems such as electrical and plumbing. A crawl space floor composed of dirt or gravel can attract groundwater, adding moisture to the area. To deal with excess moisture try the following:

  • Lay down a vapour barrier
  • Install a concrete floor
  • Add walls with insulation
  • Install a drainage system if the water pools on a dirt or gravel floor