How do I repair parging around a basement window where water keeps seeping in?

Water seeping around a basement window is rarely just a parging problem — it is almost always a combination of failed caulking, deteriorated parging, poor window well drainage, and sometimes improper grading, all of which need to be addressed together for a lasting repair. Simply patching the parging without fixing the water source will result in the same problem returning within one or two GTA winters.

Start by identifying where the water is actually entering. The most common culprit is the joint between the window frame and the foundation wall. This joint should be sealed with high-quality polyurethane caulk ($8-$15 per tube), but over time the caulk dries out, shrinks, and cracks — especially under Toronto's extreme temperature swings. Remove all old, cracked caulking with a utility knife and wire brush, clean the joint thoroughly, insert foam backer rod if the gap is wider than 6mm, and apply a fresh bead of polyurethane caulk, tooling it smooth with a wet finger or caulk tool. This joint is critical and should be inspected every 2-3 years.

For the parging itself, chip away all loose, cracked, or hollow-sounding parging around the window opening using a cold chisel and hammer. You want to get down to solid substrate — whether that is concrete block, poured concrete, or sound existing parging. Clean the area with a wire brush and rinse with water. Once the surface is damp (not wet, not dry), apply a concrete bonding agent to the exposed substrate. This step is non-negotiable — skipping bonding agent is the primary reason parging patches fail. Once the bonding agent becomes tacky, apply polymer-modified parging compound in layers no thicker than 15mm per coat. Build up to level with the surrounding parging, sloping the surface away from the window frame so water drains away rather than pooling against the glass. The repair area needs to stay moist for 3-5 days — mist with water twice daily and cover with plastic if temperatures exceed 30 degrees Celsius.

The window well itself is often the real problem. If you have a below-grade window well, check that it has at least 150mm (6 inches) of clean gravel at the bottom for drainage. Many older GTA homes — particularly post-war homes in Scarborough, North York, and Etobicoke — have window wells that have filled with soil, leaves, and debris over the decades, turning the well into a bathtub that holds water directly against the foundation. Clean out all debris, top up with gravel, and install a clear polycarbonate window well cover ($30-$80 at any building supply store) to keep rain and snow out while still allowing light through. Also verify that the grade around the window well slopes away from the foundation — Ontario Building Code requires a minimum 6-inch slope over the first 6 feet from the foundation.

For persistent seepage that continues after addressing the caulking, parging, and drainage, the issue may be deeper. Exterior waterproofing around the window area typically costs $1,500-$4,000 for a targeted excavation, or $300-$800 for interior crack injection if water is entering through a specific crack in the poured concrete wall. A professional assessment is worthwhile if simple repairs do not resolve the issue — foundation water intrusion only worsens with each freeze-thaw season in the GTA.