Crack injection (epoxy and polyurethane)

Most Ottawa homeowners meet their foundation for the first time in late March, when meltwater finds a crack that has been there quietly for years. If the wall is poured concrete and the crack runs more or less vertically, injection is usually the right repair, and it is the cheapest of the options on this site.

What is actually happening in the wall. A poured wall shrinks as it cures and cracks in the first year or two of its life. That crack is often only a fraction of a millimetre wide at the inside face and wider somewhere in the middle of the wall. Dry all summer, it becomes a pathway the moment the soil outside is saturated and the water table rises against it. Injection fills the crack through its full thickness so there is no route left.

Step one: identify the crack and the wall type. Injection works on poured concrete. It does not work on concrete block, stone or rubble foundations, which are common in the Glebe, Old Ottawa South, Sandy Hill and the older parts of Westboro, and those need a different approach from outside. A contractor who offers to inject a block wall is worth questioning.

Step two: preparation. The crack is cleaned back to sound concrete, any loose material and old patching removed, and injection ports set along its length at roughly 150 to 300 mm centres. A surface paste is then applied over the face of the crack between the ports to hold the resin in while it is under pressure.

Step three: injection. Resin is pumped in at the lowest port until it appears at the port above, which is how the crew knows the crack is full at that level. They cap that port and move up. A full-height wall crack is typically six to ten ports.

Step four: cure and clean-up. Polyurethane foams and reacts with moisture, expanding to fill irregular voids, and stays flexible afterwards. That flexibility suits Ottawa, because foundations here move seasonally. Epoxy cures rigid and structurally bonds the two faces of the crack together, which matters when the wall needs its strength restored, but it demands a dry crack and it will simply split again beside the repair if the wall keeps moving. Once cured, the ports come off and the surface paste is ground back.

How long it takes. One crack is usually two to four hours. A typical house with two to four cracks is half a day to a day. There is no excavation, no equipment on the lawn and nothing to reinstate outside. Cure time before you can paint or refinish is generally 24 to 48 hours.

What it costs in Ottawa in 2026. Indicative ranges rather than quotes. A single crack in a poured wall is commonly $400 to $800. A typical house with two to four cracks runs about $800 to $3,200. What moves the number: the height of the wall, how much finished basement has to come off to reach the crack, whether the crack is actively running water on the day, and whether the resin chosen is polyurethane or the more expensive epoxy. Removing and reinstating drywall, insulation and framing is often quoted separately, so ask.

What makes an Ottawa house different. Much of the city is built on Champlain Sea clay, often called Leda clay, which swells when wet, shrinks as it dries and can lose much of its strength when it is disturbed (NRC, Geotechnical properties of Leda clay in the Ottawa area). Foundations on it move a little every year. Add frost that drives the Building Code to require foundations as deep as 1.2 m below grade in clay soils (OBC 9.12.2.2, Minimum Depth of Foundations), plus a melt that saturates the ground around every basement in a fortnight, and you have the reason March and April are the busiest weeks of the year for this trade. It is also the reason flexible polyurethane is the usual choice here: a rigid repair in a wall that moves seasonally has a shorter life.

Who should do the work. Crack injection is not licensed work in Ontario and there is no provincial certificate for it. What you should be checking instead is liability insurance, WSIB coverage and a written warranty, and whether the contractor will put in writing that the crack is non-structural. If the crack is wider than about 6 mm, horizontal, stair-stepped through block, or the wall is bowing inward, injection is the wrong conversation and you want an assessment and probably a professional engineer, whose licence you can check in the PEO directory.

What to ask before you hire. Is my wall poured concrete or block. Polyurethane or epoxy, and why that one for this crack. How many ports and over what length. What is the warranty, how long, and is it transferable if I sell. Does the price include removing and putting back finished wall. If it leaks again, who pays. Get the warranty in writing rather than as a promise on the doorstep, and ask for photographs before and after, which insurers increasingly want to see.

Injection seals a crack. It does not stop water reaching the wall, it does not fix grading that slopes toward the house, and it will not save you if the downspout is discharging beside the foundation. Fix those at the same time or you will be paying somebody to seal the next crack along in two years.