Foundation problems
Foundation Settlement and Sinking
Part of my house seems to be sinking. How do I know if it is a real problem?
Every house settles slightly, and even settlement causes almost no damage. The version that matters is differential: one part of the foundation drops relative to another, which bends the structure above and shows up as diagonal cracks at window and door corners, doors that stick and floors that slope. The decisive question is whether it is still moving, because settlement that stabilised years ago often needs no structural work at all.
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This one splits both ways. The specifics below decide it.
What you are probably seeing
- Diagonal cracks running from the corners of window and door openings
- Doors and windows binding, sticking, or swinging open by themselves
- Floors that slope enough to notice, or that a ball rolls across
- Gaps opening between walls and ceilings, or baseboards lifting off the floor
- Drywall cracks that come back within months of being filled
- Stepped diagonal cracking in exterior brick or stucco
- A deck, step or garage slab pulling away from the house
What causes it
- Clay shrinking as it dries
- Clay loses volume as it dries out, removing bearing support from under a footing. Calgary's wet spring followed by dry summer is exactly the moisture swing that drives this.
- Poorly compacted fill consolidating
- Fill placed during construction can continue to compress for years, which is why settlement sometimes appears a decade after a house was built rather than immediately.
- Water softening the soil
- A leaking service line, a downspout discharging at the wall, or grading directing water at the foundation all reduce the bearing capacity of the soil beneath it.
- Mature trees drawing moisture from clay
- A large tree removes a substantial volume of water from the ground over a dry summer. On clay soils close to a foundation, that is a recognised settlement mechanism.
- Nearby excavation
- Digging for a neighbouring build, a utility trench or a new basement can undermine adjacent support if it is not properly managed.
How serious is yours?
The left column is worth acting on. The right column is genuinely fine to watch, and saying so is the point of this page.
Get this assessed
- Get this looked at: Cracks wider than roughly 6mm in walls above the foundation
- Get this looked at: Doors or windows that went from fine to unusable within a season
- Get this looked at: A visible step or offset in the foundation itself
- Get this looked at: Floors sloping enough to be obvious without measuring
- Get this looked at: Several symptoms appearing together in the same part of the house
- Get this looked at: Anything on this list that is measurably changing month to month
Reasonable to monitor
- Hairline drywall cracks in a house under about three years old
- One sticking door in a house that has otherwise been stable for decades
- A slope in a floor that a survey shows has not changed
- Cracks that were filled years ago and have not reopened
How it is usually dealt with
Survey and monitor
Measuring floor elevations across the house establishes how much differential exists and where. Repeating it later establishes whether it is active. Stabilised settlement frequently needs no structural repair at all, so this step can save the entire cost of one.
Correct the water cause
Regrading, extending downspouts, repairing a leaking service line. Not structural work, but often necessary alongside it, and occasionally sufficient on its own.
Helical piles
Screwed into the ground beside the footing to reach soil that can carry the load, with brackets transferring weight onto them. The common residential solution where access allows.
Push or resistance piers
Driven hydraulically using the building's own weight as the reaction force, which verifies capacity as they go in.
Slab lifting
For settled garage slabs, basement floors and walkways rather than the house footing, grout or expanding polymer is injected beneath to fill voids and lift back toward level.
The Calgary angle
Clay is the local driver. Calgary's pattern of a wet spring followed by a dry summer is the moisture swing that makes clay change volume, and volume change under a footing is precisely what removes bearing support. Mature trees deserve particular attention on older inner-city lots, where large boulevard and yard trees frequently sit within a few metres of a foundation on clay soil.
What to do next
These cost nothing and make any later assessment considerably more useful.
- Walk the house and note every sticking door, sloping floor and diagonal crack in one list
- Check whether the symptoms cluster in one part of the house, which points at differential movement
- Photograph the cracks with a scale and date them
- Look outside at that part of the house for water sources and large trees
- Ask for a floor elevation survey rather than a visual opinion, since it is the measurement everything else depends on
The repair page for this problem
If you have decided it needs attention, this is the page covering what the work involves and what it costs.
Foundation settlement repairQuestions people actually ask
How do I tell normal settling from a foundation problem?
Normal settling is uniform, small and happens early in a house's life. The signals that matter are differential: diagonal cracks from window and door corners, floors sloping in one direction, doors sticking on one side of the house only. Above all, look for change. A static hairline crack is a very different thing from one that has widened since spring.
Does foundation settlement stop on its own?
Sometimes. Settlement from a one-time cause, such as fill consolidating, can run its course and stabilise. Settlement driven by an ongoing condition, such as seasonal clay movement or a persistent water source, continues until that condition changes. Establishing which you have is why monitoring comes before any quote.
Can a sinking foundation be lifted back to level?
Often partially, sometimes fully, but full lift is not always the right objective. A house that settled over decades has adjusted to its position, and forcing it back can crack finishes, masonry and plumbing that had accommodated the movement. Stabilising at the current elevation is a common engineering recommendation, particularly in older homes.
Do trees cause foundation settlement in Calgary?
They can on clay soils, by removing large volumes of water from the ground through a dry summer and causing the clay to shrink. It is a real mechanism rather than a certainty. Removing a tree is not automatically the fix either, because soil rebounding after removal can cause movement of its own, which is worth engineering advice before reaching for a saw.
Not sure what you are looking at?
Send a description and a postal code. It goes to an independent Calgary foundation contractor who can tell you what it is.
We are a referral service, not a contractor. Your request goes to an independent Calgary foundation company.