Foundation problems
Horizontal Foundation Cracks
I have a horizontal crack in my basement wall. How bad is it?
A horizontal crack is the one crack direction that deserves prompt assessment regardless of width. It is a bending signature: it means the wall is resisting sideways pressure from the soil outside and has cracked where the bending is greatest, usually near mid-height. That is a load problem rather than a concrete problem, and it does not resolve on its own because the pressure causing it is still there.
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This is one of the few findings worth acting on without waiting to see if it changes.
What you are probably seeing
- A crack running side to side across the wall, often roughly halfway up
- The crack sometimes following a mortar joint in a block wall, producing a long straight line
- The wall possibly curving inward when you sight along it from a corner
- Sometimes a stair-step pattern in block walls that steps down toward the corners
- Occasionally water or efflorescence along the crack line
What causes it
- Lateral soil pressure
- Soil pushes sideways against a basement wall. When that push exceeds what the wall can resist, the wall bends inward and cracks horizontally at the point of maximum bending.
- Saturated soil adding hydrostatic pressure
- Wet soil pushes considerably harder than dry soil. This is why walls that stood for decades can begin moving after drainage fails, grading changes or a wet spring.
- Expansive clay swelling
- Clay-rich soil increases in volume as it takes on water, generating pressure rather than just transmitting it. Calgary's clay till makes this a recognised local mechanism.
- Frost acting on the upper wall
- Soil freezing against the upper portion of a wall expands and concentrates load high up, which can push the top of the wall inward while the base stays put.
- Surcharge from what is on the ground above
- A driveway, a vehicle parked close to the house, a new patio, fill or a retaining wall all add load to the soil beside the foundation and therefore to the wall.
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: The wall is visibly bowed or measurably out of plumb
- Get this looked at: The two faces of the crack are no longer flush with each other
- Get this looked at: The crack has widened noticeably over a season
- Get this looked at: The crack is wider than roughly 6mm
- Get this looked at: Stair-step cracking in a block wall accompanied by displacement
- Get this looked at: Fresh debris at the base of the wall, indicating recent movement
Reasonable to monitor
- Nothing on this page falls into a genuine can-wait category, which is unusual and is the reason horizontal cracking is treated differently from every other crack direction here. Even a hairline horizontal crack with no displacement is worth having measured and monitored, because the value of the measurement is knowing whether it changes.
How it is usually dealt with
Monitoring first
Where deflection is slight, crack monitors and repeat measurement establish whether the wall is actually moving. A wall that moved years ago and stopped needs a different response from one moving now, and this is the cheapest way to find out which you have.
Carbon fibre or steel restraint
Bonded straps or vertical steel bracing hold the wall against further inward movement. They stop progression; they do not straighten the wall or remove the pressure.
Wall anchors
Anchors through the wall to plates set in stable soil out in the yard. Because they can be tightened over successive seasons, they can sometimes recover part of the deflection.
Drainage correction
Reducing the water in the soil reduces the pressure. This accompanies structural restraint rather than replacing it, and skipping it is the common reason a restrained wall keeps trying to move.
The Calgary angle
Two Calgary conditions push in the same direction. Clay-rich till generates pressure as it swells rather than merely transmitting the soil's weight, and the deep frost line means a large area of wall stays in contact with soil that freezes and expands. If the crack appeared or worsened during spring melt, saturated backfill is the likely aggravating factor, which makes drainage part of the answer rather than an optional extra.
What to do next
These cost nothing and make any later assessment considerably more useful.
- Photograph the crack with a ruler or coin in frame for scale, and date the photo
- Mark the ends of the crack with pencil and the date so growth becomes visible
- Sight along the wall from a corner to check for a visible bow
- Check outside for anything adding load or water: grading, downspouts, a patio, parked vehicles
- Arrange an assessment, and ask specifically whether an engineer is recommended
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 wall repairQuestions people actually ask
When should I worry about horizontal foundation cracks?
Treat every horizontal crack as worth assessment. Unlike vertical cracks, which are commonly harmless shrinkage, horizontal cracking indicates the wall is bending under sideways pressure. Width matters for urgency, and displacement or visible bowing raises it considerably, but the direction alone is enough to justify having it looked at rather than watched indefinitely.
What is worse, a horizontal or a vertical crack?
Horizontal, in almost every case. Vertical cracks are usually shrinkage from concrete curing and often mean nothing. Horizontal cracks are a bending signature caused by external pressure. Direction is the single most useful thing you can observe about a foundation crack, and it is free to observe.
Can a horizontal crack be repaired by injection?
Injection can seal a horizontal crack against water, and it may be part of the work, but on its own it does not address why the crack formed. The wall is being pushed, and a sealed crack in a wall still under pressure will generally reopen or be joined by another. The pressure and the restraint have to be dealt with as well.
Does a horizontal crack mean my house is about to collapse?
No. Residential basement walls very rarely fail suddenly, and there is usually a long warning period, which is what a horizontal crack is. The real risk is progressive: the pressure remains, movement continues, and a wall that could have been restrained becomes a wall that has to be rebuilt.
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.