Most foundations have some cracks, and many of them are harmless shrinkage cracks. The warning signs are movement that is ongoing or uneven: cracks that are wide, growing or offset, walls that bow or lean, and doors, windows and floors that go out of square. The earlier these signs are investigated, the more options there usually are for repair.
What causes foundation problems
Foundations move when the soil underneath them changes. Common causes include:
- Water. Poor grading, short downspouts and blocked weeping tile let water saturate the soil beside and below the foundation. Saturated soil is weaker and pushes harder on basement walls.
- Clay soils. Many parts of the Prairies have clay soils that swell when wet and shrink when dry, moving foundations seasonally.
- Frost. Footings that are not deep enough, or soil left exposed under an unheated area, can heave when the ground freezes.
- Poor fill or compaction. Settlement is common where fill was not compacted properly during construction.
- Trees and drought. Large trees close to the house can dry out soil and cause settlement.
- Plumbing leaks under or beside the foundation.
Warning signs to look for
Outside the house
- Cracks in the foundation wall wider than a hairline, especially if one side is offset from the other.
- Stair-step cracking in brick or block, or cracks in brick that run through the bricks themselves.
- Walls that lean, bulge or are out of plumb.
- Gaps between the foundation and steps, porches, garage slabs or the house framing.
- Ground that slopes toward the house, low spots beside the foundation, or downspouts discharging right at the wall.
- Chimneys pulling away from the house.
Inside the house
- Doors and windows that stick, or gaps that open above doors.
- Diagonal cracks in drywall or plaster from the corners of doors and windows.
- Floors that slope, bounce or feel uneven, or gaps between floors and baseboards.
- Basement walls that bow inward or have horizontal cracks.
- Cracks in a basement slab with one side higher than the other.
- Water seepage, efflorescence (white mineral deposits) or damp patches on basement walls. See why basements leak.
Reading foundation cracks
The shape and direction of a crack say a lot about its cause. These are general patterns, not a diagnosis.
| Crack pattern | Often means | Level of concern |
|---|---|---|
| Thin vertical crack in poured concrete, no offset | Shrinkage as the concrete cured | Usually low; seal if it leaks and watch it |
| Diagonal crack from a corner or window | Some differential settlement | Moderate; monitor and investigate if growing |
| Horizontal crack in a basement wall, or inward bowing | Soil or water pressure pushing the wall in | High; have it assessed promptly |
| Stair-step crack in block or brick | Settlement or lateral pressure | Moderate to high depending on width and offset |
| Crack wider at one end, or with offset faces | Ongoing differential movement | High; have it assessed |
Our guide on concrete cracks goes into more detail on judging cracks in concrete generally.
What to do if you see warning signs
- Document it. Take dated photos with a ruler or coin for scale. Mark the ends of cracks in pencil with the date.
- Monitor. Check every few weeks, and across seasons. Crack monitors (small gauges glued across a crack) are inexpensive and show movement clearly.
- Manage water first. Extend downspouts away from the foundation, correct grading so it slopes away, and check that sump pumps and weeping tile work. Many foundation problems slow down once water is controlled.
- Get an assessment. A building inspection can identify and document the signs. If movement is significant or ongoing, a structural engineer should assess the cause and design any repair.
- Use qualified contractors for structural repairs such as underpinning, wall bracing or anchors, working from the engineer's recommendations.
Do not ignore horizontal cracks or bowing walls. A basement wall that is bowing inward is being pushed by the soil. It can get worse quickly after heavy rain or a freeze. Have it assessed by a qualified professional rather than patching over it.
Buying a home with foundation cracks
Cracks do not automatically rule out a house. What matters is the cause, whether movement is ongoing and what repair would involve. During a pre-purchase inspection, ask the inspector to point out every crack they find, explain what they think it means, and say whether a structural engineer should look at it before you firm up your offer.
How ehZee can help
During an ehZee home inspection, you can walk the property with the inspector, see the foundation signs firsthand and hear the findings on the day, followed by a written report within two days. Where movement looks significant, we will tell you plainly and recommend a structural engineering assessment.
Common questions
Are hairline cracks in a new foundation normal?
Thin vertical shrinkage cracks are common in poured concrete foundations. They usually do not affect strength, but should be sealed if they let in water and watched for widening.
Can I fix a foundation crack myself?
Sealing a small non-structural crack against water is a common homeowner or contractor job. Cracks that are wide, growing, offset or horizontal need a professional assessment of the cause before any repair.
Does home insurance cover foundation repairs?
Coverage varies widely between policies, and settlement is often excluded. Check your policy and talk to your insurer.