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Home Maintenance

How To Damp Proof Your Basement

How To Damp Proof Your Basement

Just hearing the words “damp basement” can conjure up dreaded images of musty books and ruined carpets.

Chronically damp basements affect your home’s air quality and can lead to serious health conditions. They cause peeling paint, mould and mildew, rotting wood, warped floorboards and rusty appliances.

Luckily there are many simple do-it-yourself solutions to put a stop to the dampness and get your basement back on dry footing. Pat Noble Lumber wants to share some with you.

Safety precautions when working in a flooded basement

If your basement has standing water, be sure to remove all the water before starting any work in order to prevent electrical shock.

One way to remove the water is with a garden hose and utility pump. First turn off the power in the basement. A utility pump and garden hose will help you empty the water from the basement. You can plug the pump into an upstairs electrical outlet with an extension cord.

When the basement floor is dry, you can safely begin to waterproof your basement walls.

Find the source

You’ll need to do some detective work first to find the source. Look carefully at your interior basement walls and floors to determine where the water leaks start. Check window corners, cracked mortar, and the walls around water-supply pipes and sewer pipes. Inspect the outside walls of your house for cracks in the walls, paying close attention to where the house walls meet the ground.

The main culprit of many damp basements is runoff from heavy rain and melting snow. This sudden surge of water can collect and pool, then seep through cracks in the foundation. Homes tend to settle over time, and cracks may appear in basement walls. Rainwater saturates the soil and eventually seeps through the cracks, which causes basement walls to become wet. As the water from the walls evaporates, the air in the basement becomes more humid.

Solutions for runoff

Make sure that the ground around your house slopes away from the foundation walls to avoid pooling rainwater or melting snow or ice. You can add soil around your house at a slope of one inch per foot for a minimum of six feet to help prevent water from entering your basement.

Are your downspouts in good condition or are they leaking? Replace damaged downspouts and direct them away from your home’s foundation.

Don’t forget to clean your gutters in the fall to prevent leaves from forming jams that can lead to a rush of water during the spring thaw.

Fill cracks with hydraulic cement

Luckily, sealing cracks is a simple do-it-yourself job.

You can use a hydraulic water stop cement product to plug water leaks. It expands and sets quickly to provide a reliable seal that prevents water from getting through your walls. Mix with water until it has a thick putty consistency, then press it into the cracks with your fingers or a putty knife. When the hydraulic water stop cement product is dry, apply some waterproof masonry cement on the walls to seal the concrete and prevent moisture from coming through the walls.

Keep a close eye on your walls especially after a heavy rainfall, to ensure there are no more entry points for water.

Condensation in your basement

Chances are there is condensation building up on the walls or floor of your basement.

To find out exactly where, attach a one-foot square piece of aluminum foil to a part of the wall that you have thoroughly dried with a dry cloth.

After 24 hours, remove the foil and feel the inside of the foil for moisture. If the foil is wet, then water is most likely coming through the wall from the exterior. If the foil is dry, the moisture is likely coming from another part of the basement.

Condensation solutions

To solve condensation issues, open windows and use fans to get the air circulating. You can also install a dehumidifier to help dry your basement, and keep it running to maintain a low level of humidity. Do you have a bathroom with a shower in the basement? Check that you have an exhaust fan in good working condition to push damp air to the outside and keep the room well ventilated.


Another cause of floods in basements is groundwater levels that naturally continuously rise and fall, and can lead to water seeping up from your basement floor and through cracks.

Your home may be built in an area where the water table is higher, or there may be underground springs near your house. It’s advisable to learn as much as you can about your home’s situation by contacting your municipality.

Solutions for groundwater moisture

The amount of clay in the soil around your home will affect how much water seeps into your basement from groundwater. If your soil does not contain much clay, you can have clay added to the soil around your house to slow down the amount of water that escapes to your basement from groundwater.

Sump pumps are a must-have for any basement that has water seepage. As soon as water levels get too high, the sump pump automatically springs into action to pump water out of your basement and away from your property.

It’s a good idea to get a sump pump installed by a professional. If you already have a sump pump, check it periodically to ensure it is in good working order.

If your groundwater seepage problem continues or worsens, you may need to consider contacting a professional. They can install an interior system to channel water away through PVC drain pipes in gravel foundation footings. Another more costly method is to excavate around the house and install a waterproof membrane.

Be sure to get at least three estimates from companies before moving ahead. It's also a good idea to ask friends and neighbours for recommendations of reputable companies.

Window well leaks

Another possible cause of a damp basement is leaking from window wells. Sometimes when rainwater or melting snow has nowhere to go, the water pools near the basement window and starts to seep in. This leads to moist basement walls, water puddles and flooding during the rainy season or spring thaw.

Window well solutions

Check window wells and make sure they have a properly installed drainage system. It’s always best to install a good window well drainage system right from the start, but it’s never too late to put one in. Monitor your window wells and keep them clear of snow, mud, gravel, weeds and leaves to prevent blockages in the drain. You can keep rainwater moving away from your basement and foundation by installing a sloped window well cover.

Investing a little time and effort today to damp-proof your basement will pay off in so many ways, and will help prevent serious problems caused by moisture. You’ll gain peace of mind and protect your possessions and home while ensuring a safer and healthier environment for your family.

If you have any questions or need more information, feel free to visit Pat Noble Lumber for assistance. We would be happy to help you in any way we can.

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