When should I worry about horizontal foundation cracks? Take every long sideways crack seriously, and worry most when it grows, lets in water, or comes with a wall that bows in. A concrete trade group says horizontal cracks are most likely caused by a load pressing on the wall. Someone needs to see it in person.
If you think the wall leans, our guide to bowing basement walls shows the signs to look for.
Quick summary
A sideways crack often means soil is pushing in. Winnipeg clay swells when it gets wet, and frost in the ground can push on the same wall in much the same way. Mark both ends and take a dated photo each time, so you can see any change, then ask someone to look at it in person.
What does a horizontal crack in a basement wall mean?
It usually means the wall has been pushed. An engineer who writes for a home inspector group in the United States says a horizontal crack shows the wall has moved sideways. As it moves, the crack opens on the inside.
He blames wet soil, frost and surface water, and a guide from the Concrete Foundations Association also points to a load on the wall.
Block walls need extra care. The same engineer says block walls resist sideways push less well than poured concrete, so a horizontal crack in one deserves a close look.
Foundation cracks, horizontal vs vertical: which is worse?
Most cracks are no cause for alarm. Shrinkage cracks run up and down or at an angle, and a trade group says they pose no structural concern unless they leak or shift.
A Saskatchewan guide says new concrete cracks as it dries and shrinks, and the home inspector article calls hairline cracks like these cosmetic.
Sideways cracks differ. They point to a force from outside the wall, and that force usually comes from the soil packed against it.
Why does Winnipeg clay push on basement walls?
Winnipeg sits on clay. A University of Manitoba study found most homes here sit on shallow footings, and the clay's swelling and shrinking caused cracks and uneven floors.
The same survey found about 94% of the Winnipeg houses it looked at had some damage. Most was minor.
Wet soil expands and can push the wall in, which opens the crack, says the home inspector article, while dry soil may let it close.
Frost does the same. The article warns that rain and snow melt, followed by freezing weather, can make a wall move and crack all at once.
Which signs mean a sideways crack needs a look soon?
Watch for these signs.
- The crack is getting longer or wider.
- It leaks after rain or a thaw.
- The middle of the wall bulges in.
- You see a second horizontal crack.
- Step or vertical cracks join it.
The home inspector article says several horizontal cracks stacked above each other often mean the wall has moved more than once. Mixed crack types are a warning too.
Get help soon for long horizontal cracks. The Concrete Foundations Association says so, and the Government of Canada adds cracks that keep growing or let water through.
How do you track a crack between visits?
Start with a pencil. The Government of Canada suggests marking both ends of a crack so you can see if it grows or turns.
Take a dated photo next to a tape measure each time you check, and keep the photos in one album. Check after each big rain.
Sight along the wall from one end. Corners rarely move, the home inspector article notes, so a wall that sits farther in at the middle may have shifted.
A long level or a plumb line helps here. The home inspector article suggests measuring over the full height of the wall, then comparing that number with the same reading at a corner.
Write each reading down. Small changes are easy to forget, and dated numbers are easy to share with whoever comes to look.
Can a horizontal crack close up again?
It can. The home inspector article says it can close as clay dries, but if soil settles behind a bowed wall, the wall stays put. Keep tracking it.
Does a builder warranty cover a horizontal crack?
It depends. A Saskatchewan concrete guide says a typical basement warranty covers a crack only when it leaks, has shifted, or is wider than 3 mm. Read yours.
Should I call an engineer or a contractor first?
Either can be a first step, and the right choice depends on what you see and how fast it is changing. Ask whoever visits to explain what they found in plain words.
Is a horizontal crack outside the house a warning sign too?
Yes. The home inspector article says that when a wall is pushed in, a matching crack can show up outside near the base of the wall. Photograph both.
Brick on the outside can show it too. The same article says a pushed-in wall can tip out at the top, and the brick resting on it may tip or crack as well.
Want a second set of eyes on the wall?
Take one photo along the length of the wall and another close to the crack with a tape measure beside it. Then read our wall bracing page to learn what steel bracing is and what to ask about it.
If you are already comparing quotes, our post on what changes the price of fixing a bowed wall covers what to ask.