What to do when your basement floor is damp

by Kristina Hemmerling

If your basement floor is damp, the source is either leaks from pipes and the outdoors or condensation from high interior humidity levels. You must find the cause of your basement moisture problem before water causes mould or structural damage to your home. [Image credit: iStock.com/Wildroze]

What to do when your basement floor is damp

If your family avoids the basement for its cold, clammy atmosphere or if you avoid storing items in the basement because they get a musty odour, you have a moisture problem. It may not be a visible leak, but it definitely needs to be addressed. Here’s how.

Figure out the cause

How can you tell if your basement floor is damp due to leaks or condensation? Consider the following:

  • Location: If the dampness is occurring below a bathroom or just in certain corners of the basement, this could be a sign that you have leaking pipes or a condensation problem from an improperly ventilated bathroom.
  • Severity: Small patches of dampness could indicate a leak while large areas of dampness often indicate humidity problems.

The easiest way to figure out whether you have a leak or a condensation problem in your basement is to tape a section of aluminium foil to your basement wall. After a few days, inspect the foil. If there is moisture on the outside surface of the foil, this indicates that you have high indoor humidity. If there is moisture behind the foil on the wall, this indicates that you have water leaking in through the walls.

Stop leaks

Water can get into your home through leaks in the foundation, from small gaps around windows and doors or from leaking pipes. If you’ve determined that your damp basement floor is being caused by a leak, you may need to work with a plumber or basement waterproofing company to repair the source of the leak.

After fixing the leak itself, you’ll want to take the following measures to prevent further leaks in your basement:

  • Let water drain away from your foundation by re-grading the ground if necessary
  • Clean eavestroughs and extend downspouts to direct rain away from the foundation
  • Plug holes and cracks in the foundation with hydraulic cement
  • Waterproof the walls with several coats of special paint
  • Install/ensure your drainage system or sump pump is working properly
  • Get any pipes, toilets or showers that are leaking fixed

Reduce indoor humidity

Condensation in your basement comes from high levels of indoor humidity. Indoor humidity can be caused by daily activities such as showering, cooking and drying clothes without the proper ventilation system in place. If you leave your indoor humidity at high levels, it can lead to dampness and moisture problems, making it the perfect breeding ground for mould and other allergens.

There are several steps you can take to reduce indoor humidity in your basement and get rid of the dampness:

  • Seal leaky dryer vents with foil tape
  • Add a vent fan to your basement bathroom
  • Close windows during humid weather
  • Run a dehumidifier
  • Insulate pipes with foam covers
  • Insulate exterior walls with rigid insulation under drywall

It’s important to know what to do if you find that your basement floor is damp. If you ignore the problem, dampness and moisture in your basement can lead to serious water damage problems such as rot, structural damage, and mould and mildew growth, which can lead to health problems. If you suspect the presence of mould, contact a mould remediation expert for help. If you’ve tried the steps listed above and still find moisture on the walls or dampness on your basement floors, you should contact a ventilation expert or a waterproofing expert for further advice.

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