Brockville sits on the north shore of the St. Lawrence River, and like the rest of the 1000 Islands area it has cold winters with repeated freezing and thawing. Those swings are hard on foundations. Snow piles up for weeks, then a mild spell or a winter rain turns it to water in a day or two. That water has to go somewhere, and too often it ends up in the basement.
This guide explains the common causes of thaw leaks, the checks homeowners can safely do themselves, the warning signs to watch for and the point where it makes sense to have a professional look at the problem.
What Happens Around a Foundation During a Thaw
Snowmelt collects right against the walls
Snow cleared from driveways, walkways and roofs usually ends up piled beside the house. When it melts, the water soaks into the soil directly against the foundation. A large snowbank can release a surprising amount of water into a small area, all of it beside your basement walls.
The ground is still frozen below the surface
During a midwinter thaw, the top layer of soil may soften while the ground beneath stays frozen. Meltwater cannot soak down and away as it would in summer. Instead it spreads sideways and follows the easiest path, which is often the loose backfill beside the foundation.
Frozen eavestroughs and downspouts
Ice can block eavestroughs and downspouts, and downspout extensions are often buried under snow or frozen solid. When that happens, water from the roof spills over the edge or pours out at the base of the wall instead of being carried away. Ice dams at the roof edge can make this worse.
Saturated soil and hydrostatic pressure
Once the soil around the foundation is full of water, that water presses against the walls and floor. This is called hydrostatic pressure. It pushes water through any weakness it can find: the joint where the wall meets the floor, tie holes, gaps around pipes and cracks in the concrete.
Cracks that open with the cold
Freezing and thawing make soil expand and contract, and foundation walls move slightly with the seasons. A hairline crack that stays dry in summer can open enough to let water through when the soil outside is saturated. A crack that leaks every spring is unlikely to fix itself.
Checks You Can Do Yourself
Many thaw leaks can be reduced with simple maintenance. Do these checks before a forecast melt if you can, and always put your safety first on ice and snow.
Move snow back from the foundation
Shovel snow away from the walls so there is a clear strip next to the house, especially on the sides where snow from the roof or driveway piles up. Pile it where the meltwater will drain away from the house rather than toward it.
Clear downspout extensions
Make sure each downspout has an extension that carries water well away from the foundation, and that the path is not buried or frozen. Dig out the outlet if needed. If an extension is frozen solid, avoid hammering or chipping at it, and avoid chipping ice off the foundation with metal tools, since that can damage the parging, the wall coating or the pipe itself.
Check the window wells
Window wells collect snow and then fill with meltwater. Scoop out snow and ice, check that any drain at the bottom is clear, and consider a cover to keep snow out. A full window well can push water through the window frame and into the basement.
Look at the grading
Once the snow is gone, notice where water pools. Soil should slope away from the house. Low spots next to the foundation are worth filling and regrading in spring or summer.
Test the sump pump
If your home has a sump pump, test it before the melt by slowly pouring water into the pit and watching it start, empty the pit and shut off. Our guide to sump pump failure in winter covers this in more detail.
Warning Signs to Watch For
- Damp patches or puddles that appear after a mild spell or a winter rain.
- Water seeping at the joint between the wall and the floor.
- A crack that darkens, drips or leaves a rust coloured stain.
- White chalky deposits on concrete or block walls, a sign water has been passing through.
- A musty smell, or damp cardboard boxes and carpet.
- Water around the window frames or at the bottom of a window well.
- A sump pump that runs much more often than usual.
Take photos and note the date and the weather each time you see water. That record is very useful when tracing the source.
Safety First
Keep electrical cords, extension cords and appliances away from any water on the basement floor. If water is near outlets or the electrical panel, do not walk through it; call an electrician or your utility. Move valuables off the floor and start drying wet materials quickly to limit mould growth.
When to Call for an Assessment
Basic maintenance solves some thaw leaks. If water keeps coming in after you have moved the snow, cleared the downspouts and checked the window wells, the problem is likely in the foundation or its drainage.
A wet basement repair assessment traces where the water is actually entering. A leaking crack in a poured concrete wall can often be sealed from inside with foundation crack injection. When the weeping tile has failed or the walls seep in many places, exterior foundation waterproofing addresses the problem from the outside once ground conditions allow digging.
The best time to plan is soon after you notice a problem, while the signs are fresh and before the next thaw. You can also browse our frequently asked questions for more general answers.