Basement Moisture Remedies - Sutton — Canadian Real Estate Listings & Agents |

Basement Moisture Remedies

03 June 2019

Basement Moisture Remedies

Is your basement generally cold, dark and damp, but you envision it as a fabulous living area and possibly an income earner? You are not alone. Homeowners renovate basements to create rental suites, home-based businesses, or extra space for a theatre system, bar, music studio, fitness centre, or even a luxury spa with an infrared sauna.

A basement renovation is an attractive way to add usable square footage because compared to an addition, it is typically less expensive and the municipal permit process less complicated.

Before you spend money remodelling your basement, check for moisture problems. Leaks and high humidity can cause stains, mildew and mold that will eventually ruin floors, walls and furniture.

Signs of moisture:

  • If you see areas of white or gray crust on the basement walls, that’s efflorescence: mineral deposits left behind by evaporating water. If patches of the wall are flaking off, this is a condition called spalling. These scenarios are the result of too much ground moisture penetrating the walls.
  • Although it is common for cracks to appear in the basement floor as a new house settles, if the cracks increase over the years, that is a problem. Hire a structural engineer (not a contractor or waterproofing expert) to diagnose the problem in writing and suggest a repair.
  • The experts at This Old House recommend a simple moisture test. Begin by taping large sheets of plastic to the basement floors and walls. Check the sheets after a couple of weeks. If condensation forms underneath, your foundation is not properly sealed. If droplets form on top of the plastic, your basement needs dehumidifying.
  • Rotted wood is another sign of moisture. Check for damage in wooden joists and window frames by probing key areas with a small, pointed awl tool.
  • Check to see whether floor joists are sagging.

(Although not moisture-related, test for radon, a radioactive gas, as well as carbon monoxide, which is a by-product of burning wood or gas in fireplaces and appliances.)

Barring a leaky pipe, moisture generally seeps into a basement from the surrounding soil through hydrostatic pressure. The more water in the soil, the greater the pressure. Sometimes this is the result of rain gutter runoff. If your rain gutters are depositing water within three metres of the house, install rain gutter diverters to deposit water further away. (Even if you decide against a basement renovation, it is important to do this.)

Too much water can also reach a home built at the bottom of a slope. Ideally, correct the slope and/or upgrade the drainage tiles. Modern drainage tile is not tile at all, but rather a system of porous plastic pipes buried in the soil surrounding the home’s foundation. It collects and diverts water downhill away from the foundation using gravity or with a sump pump to ultimately send water to storm drains or distant ground.


  • Seal small gaps around pipes with concrete-patching compound.
  • Fill small floor cracks with hydraulic cement, which expands as it cures.
  • Use foam insulation sleeves around water pipes to reduce condensation.
  • Seal the concrete using a specialized product such as RadonSeal, which is designed to block moisture and radon.
  • Install a sump pump system.

Even after you have made the repairs necessary for a dry basement, be prepared for the unexpected. A particularly wet spring or a burst pipe can cause a flood, so choose materials that can tolerate high moisture. For example:

  • Mold can grow on standard drywall paper and the gypsum core can crumble. Instead opt for moisture resistant drywall products such as USG Mold Tough Gypsum panels.
  • Avoid hardwood and laminate flooring that may buckle and stain in a flood. Instead, consider vinyl planks or tile. If you prefer the softness and warmth of carpeting, choose synthetic fibres that offer more mold and mildew resistance than natural fibres (e.g., wool, sisal, cotton).
  • On basement walls. use a vapor barrier and rigid foam insulation followed by a stud frame and drywall. Another option is to use an interlocking panel system designed for basements and affixed with the appropriate concrete fasteners.
  • If you add a washroom to the basement, hire a plumber to install a backflow-prevention valve on your main drain line. This will prevent backups into below-grade sinks or tubs.

Although renovating a basement requires planning and special care, it will reward you with valuable space.

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