Blog · Kitchener
Why Porches, Sunrooms and Additions Pull Away from Kitchener Houses
A crack that opens where a porch, sunroom or rear addition joins the main house is one of the most common foundation calls in Kitchener. The main house is usually fine. The problem is what the addition is standing on.
Last updated September 25, 2026 · Reviewed by the Kitchener Foundation Repair team
The main walls of most Kitchener houses sit on footings well below the frost line, under a heated basement. Porches, sunrooms, mudrooms and rear additions are a different story. Many were added decades after the house was built, some by owners rather than builders, and a lot of them stand on shallow piers, a thin slab or footings that never went as deep as the house. When the soil under them moves and the house does not, the joint between the two opens up.
Signs the addition is moving, not the house
- A vertical or tapered gap where the addition wall meets the house siding or brick, wider at the top or the bottom.
- Caulking or flashing at that joint that has torn, and new leaks at the roof tie-in.
- A sunroom or porch floor that slopes away from the house.
- Doors between the house and the addition that stick in one season and swing freely in another.
- Cracks in the addition's own foundation or slab, while the main basement walls show nothing new.
If the gap changes with the seasons, wider in late winter and closing in summer, frost is almost certainly involved. If it only ever gets wider, the addition is settling.
Frost, clay and how deep footings are supposed to go
Much of Kitchener is built on clay and silty soils. Clay holds water, and water in the ground freezes and expands. The Ontario Building Code deals with this in Article 9.12.2.2, which sets minimum foundation depths by soil type. For clay or soils that are not clearly defined, the table requires a depth of 1.2 m. Where the foundation does not enclose heated space, the requirement is 1.2 m but not less than the depth of frost penetration. For silt without a heated space, footings must be below the depth of frost penetration.
A heated basement keeps the soil beside the house footing from freezing hard. An unheated porch or a three-season sunroom does not get that benefit. So an addition on piers or a slab that stops short of frost depth sits in soil that freezes, lifts it a little, and lets it down again every year. Over enough winters it rarely comes back to where it started. Settlement is the other half of the problem: additions built on backfill beside the original foundation wall, which is loose soil that was dug out and pushed back, can keep compressing for years.
This pattern turns up across the city, from the 1960s and 70s subdivisions in Forest Heights and Stanley Park, where many houses gained a rear family room or sunroom, to rural-edge properties around Breslau with enclosed porches on old farmhouses.
What the repair options are
The foundation contractor starts by measuring: how far the addition has dropped relative to the house, whether the movement is seasonal, and what the addition actually sits on. That often means digging a test hole at one corner. The repair follows from what is found.
- Piering. Steel piers are installed down to firmer soil or to a depth that frost does not reach, and the addition is supported on them. Where the structure has dropped, it can sometimes be lifted part of the way back. See settlement and piering.
- New footings. For a light porch, it can be simpler to support the structure temporarily, remove the shallow piers and pour footings to the correct depth.
- Underpinning. Where an addition has a full foundation wall that stops short, the wall can be extended down in sections. See underpinning.
- Rebuild. Occasionally the porch or sunroom is in poor enough shape that rebuilding it on a proper foundation is the sensible answer, and the foundation contractor will say so.
Whatever holds the addition up, the joint to the house needs to be rebuilt afterwards: new flashing, a proper movement joint and sealing. Sealing the gap without fixing the support just hides the movement for a season.
Permits in Kitchener
The City of Kitchener lists constructing an addition, and building a porch or deck more than 24 inches above grade, among the work that needs a building permit. Replacing the foundation under an existing addition is structural work, and new piers or footings are normally designed by an engineer and covered by a permit. The contractor pulls the permit where one is needed. If you are not sure, the City's building division can be reached at 519-741-2312.
A related point for anyone buying a house: if an addition has no permit history, that is worth knowing before closing, because it tells you the footings may never have been inspected.
What not to do while you wait
- Do not fill the gap with expanding foam or rigid caulk. It hides how much the joint is moving and makes it harder to measure.
- Do send the downspouts from the addition's roof well away from its foundation. Water dumped beside a shallow footing makes both frost heave and settlement worse.
- Do mark the gap. A pencil line and a date at the top and bottom of the crack, checked each month, tells the contractor more than a single photo.
How much the fix costs depends mostly on the method and how many piers or how much footing is needed; the foundation repair cost guide for Kitchener explains the ranges. To have the addition measured, book a visit.