How Do I Seal a Leaky Basement?

If you are home has a leaky basement, naturally it is a source of concern. Moisture can not only ruin wood, drywall, and carpets in a finished basement, but it will also promote mold. Mold is dangerous to human health as the spores may be inhaled into the lungs causing respiratory problems. If you are wondering whether it is possible to repair a leaky basement yourself, the answer really depends on the cause of the water.

Here are some of the most common reasons why your home’s basement may be leaking:

  •  Roof water – the water that flows from your roof is not being carried away properly by your eavestroughs and downspouts. These devices must be free from debris and leaks to do their job properly.
  • Over-watering – perhaps someone is over zealous with the hose when watering the flowerbeds or shrubs around your home.
  • Groundwater – there is always water underground, but sometimes it is redirected towards your home because of changes in the landscape. Other times it is drawn up under the building by capillary action. This can usually be identified by a white residue on the floor. This is mineral deposits after the water has evaporated.
  • Runoff – Snow and rainwater can collect in depressed areas and then leach into your basement.
  • Bad drains – drains can be improperly installed, damaged or clogged. Sometimes underground drains do not have enough of a slope to move moisture away from the building.
  • Broken lines – water and sewage lines do deteriorate over time and may rupture. Other times tree roots can penetrate the pipes.
  • No ventilation – if air cannot circulate in the basement, humidity will build up inside the structure. To check if you have a humidity problem or a leak, tape a 1’ square of aluminum foil on the wall and leaving it overnight. If you find condensation on the room side of the foil, you know it is humidity that is causing your problems. If moisture is on the wall side, you’ve got water coming in from the outside.

To repair water leaks, there are some DIY fixes any homeowner can try. Let’s take a look at some of these methods: 

  1. Vertical crack Toronto foundation basementThe first thing you must do in all cases is to fill all of the cracks and gaps in the wall that are under 1/8-inch wide with polyurethane caulk made for concrete. If there are larger cracks that need filling, use epoxy filler.
  2. Next, you can choose one of the many commercial products on the market to help seal the cracks, including concrete waterproof coatings, silicate-based sealers, waterproofing paint and interior water-control systems.
  3. Add your waterproof coating to the filled crack. Concrete waterproof coatings go on like cement over top of most finishes. However, silicate-based sealers are intended for untreated surfaces as they need to chemically react with bare concrete. Waterproofing paint is a heavy latex paint meant to seal the wall with an acrylic layer.
  4. Interior water-control systems involve wall vapour barriers and drip moldings to collect water coming from wall cracks and other foundation wall defects. A drain then directs the water to a sump pump and finally the sump pump directs the water out of the basement. While a DIY homeowner may attempt this, it is an extensive project, and requires proper attention to getting the job done right. In some cases, calling a professional to assist is highly recommended.

Sump pump installation in Toronto basementIf your DIY methods do not work, or you cannot access your basement walls to do the repairs, you will need to call in a contractor. They will excavate around the foundation, seal the leaks and wrap the foundation in a waterproof membrane. New weeping tiles are placed near the foundation and the soil is backfilled. If you are still having issues controlling water, it may be necessary to install a sump pump. 

It is always better to call a professional sooner, rather than later. Water damage can be expensive and the long-term effects are cumulative.

Contact Nusite Waterproofing to for a free in-home estimate and inspection of your basement water problems.  We service Toronto and the surrounding GTA.


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NuSite Group is a Toronto based basement waterproofing and foundation repair company that specializes in Basement Waterproofing, Basement Lowering, and Foundation Repairs. Call us today at 416-622-7000 or 905-731-1228 for a free in-home estimate and inspection.

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Customer Testimonials

Interested in working with us? Check out some of our customer testimonials below and find more on Homestars. We are one of the highest rated basement waterproofing companies in Toronto

Mark Lipton - Homestars Review

Basement Waterproofing

Our basement leaked! Of course . . . we bought a 100 year old house! But my office needed to be in the basement permanently. I interviewed 10 different companies until we decided on the Steinbergs and their crew at Nu-Site! They are professional, reliable, courteous, honest, and they really make an effort to communicate with the client about every step of the process.

Sara Jack - Homestars Review

Foundation and Waterproofing Repairs

After several years of chronic leaks, we decided to have our basement waterproofed once and for all. The team over at Nusite was professional, answered my questions during the project and stayed within their quoted price....which is always a concern for me when working with contractors. Great job overall

Joshua Persaud - Yellowpages Review

Basement Waterproofing

Had several cracks in my basement wall and they would leak whenever we had a heavy rain. It started about a year and a half ago and seems to have gotten worse over the past 6 months. I tried having my neighbor seal it, but it started leaking again within a few weeks. Called several waterproofing companies and got several quotes. Finally went with Nusite contractors for the job. They gave a reasonable quote and I liked the guy that came by for the estimate. They stayed within budget and cleaned up before they left. It's been almost 3 months now and it seems to be working great.