Leaking Basement? What to Check Before You Call a Contractor

You head downstairs and your sock lands in something wet. Maybe it’s a puddle by the wall, a damp patch of carpet, or a dark stain creeping across the floor. Your first thought is probably “how bad is this?” and your second is “who do I call?”

Before you spend money, it pays to spend twenty minutes working out where the water is actually coming from. A leaking basement can be a crack in the foundation, but it can also be a window well, a pipe or plain condensation, and each one has a very different fix. Here’s how to narrow it down, and when it’s time to call a pro for basement and foundation leak repair.

First steps

Deal with the water first, then play detective.

1. Protect your belongings. Move boxes, furniture and electronics off the wet floor. Pull back wet rugs and get air moving with fans or a dehumidifier. If water is near outlets or appliances, be careful, and if in doubt, turn off power to that area.
2. Photograph everything. Take wide shots and close-ups of the water, any cracks, stains and the surrounding wall. Photos help any contractor, and you may want them for your insurer.
3. Note the weather and the time. Has it been raining hard for days? Did the water appear during the storm, hours later, or on a dry day? Write it down. This is often the biggest clue.
4. Check the obvious. Look at the washing machine and its hoses, the hot water tank, the furnace drain, laundry sinks, toilets and any pipes overhead. A plumbing leak can look a lot like a foundation leak, and it needs a plumber, not a concrete specialist.

Find the source

If plumbing isn’t the culprit, work through these common sources one at a time.

A crack or tie hole in the wall

Look along the wall above the wet area. Is there a crack that’s darker than the concrete around it, or has a wet edge? Small round spots in a regular grid pattern on a poured wall are tie holes, left by the metal ties that held the forms together during the pour. Both can let water through when the ground outside is saturated. White, chalky deposits (efflorescence) around a crack mean water has been coming through for a while.

The floor-wall joint

If water appears as a thin line where the wall meets the floor, it’s likely coming through the joint between them. This is a cold joint: the wall and floor were poured at different times and never fully bonded. When groundwater rises after heavy rain, it pushes up and in at this seam.

A window well

If the water is below a basement window, go outside and look at the window well. Is it full of leaves, soil or standing water? A well that doesn’t drain holds rain against the wall, and that water finds its way through small cracks around the window.

Plumbing or penetrations

Check where pipes, the water main or conduits pass through the foundation wall. The gap around a pipe is a common leak point. If water appears around a pipe only when it rains, it’s coming from outside. If it’s there all the time, check the pipe itself.

Condensation (the foil test)

Sometimes the “leak” is moisture from inside air condensing on cold concrete, especially in humid weather. To check, tape a square of aluminium foil or plastic sheet tightly to the damp wall and leave it for a day or two. If moisture forms on the room side of the foil, it’s condensation. If it forms behind the foil, against the concrete, water is coming through the wall. CMHC’s guide Moisture and Air has more on controlling condensation in basements.

Common leak points in Lower Mainland basements

Homes across the Lower Mainland and Fraser Valley see a long wet season, and a lot of basements here are poured concrete. The leaks we see tend to come from the same few places:

• Poured walls with tie holes that were never properly sealed.
• Settlement and shrinkage cracks, often vertical, that let water in once the soil outside is soaked.
• Window wells with clogged or missing drains.
• Pipe penetrations where services enter the house.
• The floor-wall joint, especially when the groundwater rises after heavy rain.

If your water shows up mainly after storms, our article on why foundation walls leak after heavy rain explains what’s going on.

Can you fix a leaking basement yourself?

Some of it, yes. Here’s the honest version.

What helps: keeping water away from the house. Clean your gutters, make sure downspouts carry water well away from the foundation, clear leaves and soil out of window wells, and check that the ground next to the house slopes away rather than toward it. These are cheap, useful jobs, and they reduce the water pushing on your walls.

What rarely works: surface sealers, caulk and paint-on products from the hardware store, applied over a leaking crack. Water pushing from behind the wall pops them off or simply goes around them. They may look fine in a dry spell and fail at the first big storm. Some also hide the crack, making it harder to see what’s happening later.

If a crack is actively leaking, it needs to be opened up and properly treated through the concrete, not covered over.

Leak repair vs full basement waterproofing

You’ll hear both terms, and they’re not the same thing.

Leak repair fixes the specific places water is getting in: a crack, a tie hole, a joint, a pipe penetration. If you have one or two clear leak points, this is usually where to start. It’s targeted and less disruptive. See our crack repair page for the defects we treat.

Basement waterproofing treats whole walls or large areas, either from outside (excavating and applying a membrane) or from inside (crystalline treatment across the wall surface). A contractor may recommend it when water is coming through in many places, or when the whole wall is weeping.

We’ll tell you which one your basement needs after we’ve looked. For the inside-versus-outside question, read interior vs exterior waterproofing.

What happens when you call us

1. Free inspection. We come out and look at the leak and the walls around it. The quote comes from a site look, not a phone guess.
2. The plan. We explain what’s leaking and what we’d do, in plain terms. If something else is contributing, such as a gutter, a window well or a crack that needs an engineer, we’ll tell you.
3. The repair. We repair leaks from the interior using Kryton’s Krystol crystalline waterproofing system, so there’s often no need to dig up your yard. If the leak is running, we can seal it while the water flows. In fact, we prefer it, because it shows us exactly where the water comes in.

As one homeowner put it: “Fraser Valley Concrete fixed my basement leak and also let me know what I could do to prevent a problem elsewhere before it happened! Thanks!” (Jon Naske, Homeowner)

Common questions

Why is water coming up where the floor meets the wall?

That seam is a cold joint, where the floor slab and the wall were poured at different times and never fully bonded. When heavy rain raises the groundwater around your house, the water pushes against the foundation and finds that joint. It’s one of the most common leak points in Lower Mainland basements, and it can usually be repaired from inside.

Is it condensation or a leak?

Try the foil test. Tape a square of aluminium foil or plastic sheet tightly to the damp spot and leave it for a day or two. Moisture on the room side means condensation from humid indoor air. Moisture behind it, against the concrete, means water is coming through the wall. Condensation is a ventilation and humidity issue; a leak needs repair.

Can I seal a basement crack myself?

You can try, but surface sealers and caulk rarely hold against water pushing from outside, especially during heavy rain. They often fail at the first big storm and can hide the crack. The DIY jobs that really help are cleaning gutters, extending downspouts, clearing window wells and checking the grading. A leaking crack needs to be opened up and treated properly.

Does home insurance cover a leaking basement?

That depends entirely on your policy and the cause of the water, so it’s a question for your insurer or broker, not us. Call them early, before repairs start if you can. Photos of the water, the damage and the date it happened will help with any conversation you have with them.

How fast can you come look at it?

It depends on our schedule at the time, so the best thing to do is call us at (778) 686-2221. We’re open Monday to Saturday, 8:30 AM to 5:00 PM. In the meantime, take photos, note when it leaks and move your belongings out of the way.

Book a free basement leak inspection

Found water in your basement? Do the checks above, take your photos, and then give us a call. We repair leaking basements across Burnaby, Vancouver, Richmond, Surrey and the Fraser Valley. Learn more about our basement and foundation leak repair, call (778) 686-2221, or request your free inspection.