Are Vertical Cracks in Foundation Bad? How to Read Yours

Are vertical foundation cracks normal?

Yes. A thin vertical crack in a poured concrete wall is the most common foundation crack there is, and it’s usually shrinkage. Concrete shrinks as it dries, and the wall cracks where it can’t shrink freely.

Pillar To Post’s inspectors describe a shrinkage crack in a poured wall as not structurally significant (opens in a new tab) and give four ways to recognize it:

• It’s small, usually less than 1/8 inch wide.
• It’s vertical.
• It stays in the foundation wall and doesn’t continue up through the house.
• It’s usually in the middle third of the wall’s length. A crack toward the end of a wall probably isn’t shrinkage.

The concrete industry agrees. The National Ready Mixed Concrete Association says some cracking is normal in concrete basement walls (opens in a new tab) and isn’t necessarily a sign of poor materials, poor work or a structural problem.

How do you tell shrinkage cracks from settlement cracks?

Look at the shape and the location. Shrinkage cracks are thin, even in width and near the middle of the wall. Settlement cracks are usually wider at the top, closer to a corner, and often keep going into the wall, siding or drywall above the foundation.

ASHI’s Tom Feiza describes a settlement crack as open at the top and tighter at the bottom (opens in a new tab), caused by the footing under the wall moving down or tipping. He adds that there’s often a crack in the floor where the footing has started to drop.

A settlement crack isn’t automatically a structural emergency. Pillar To Post says that in most cases the crack itself has no structural significance; the concern is whether the house will keep settling (opens in a new tab). Most settlement happens early and stops.

The two sides of a settlement crack should fit together like puzzle pieces. Pillar To Post warns that if the faces have moved any other way, as in a shear crack, the 1/4 inch rule doesn’t apply and it can be a significant structural concern (opens in a new tab).

When is a vertical crack in a foundation wall serious?

When it’s wide, tapered, offset, growing or part of a group of cracks. Feiza puts it this way: vertical cracks are an issue if they are wide, tapered from top to bottom, or found in combination with other cracks (opens in a new tab). Width alone doesn’t decide it.

Have a structural engineer look at the wall before you repair anything if you see any of these:

• 1/4 inch or wider. That’s the line where a settlement crack becomes more likely to be ongoing movement, and where DIY injection kits stop.
• Clearly wider at the top than the bottom. That’s the settlement shape.
• Offset edges. Feiza says vertical cracks with horizontal or shear movement always indicate a problem (opens in a new tab). Run your hand across the crack: you shouldn’t feel a step.
• Getting wider. The NRMCA says to seek professional advice for active cracks that are widening with time (opens in a new tab).
• A repair that cracked again. A sealed crack that reopens wider than a hairline can mean the wall is still moving.
• Other signs at the same time. Horizontal cracks, a bowing wall, doors that start sticking upstairs or a crack in the floor along the same wall.

If any of these fit, the engineer vs contractor guide explains who to call first. The when to worry guide covers the width rules for every crack direction.

Is a vertical crack in a block foundation different?

Yes. In a concrete block wall, a vertical crack runs through the mortar joints and sometimes through the blocks. Feiza says cracks in block walls should be very narrow, without horizontal movement (opens in a new tab).

Block walls more often crack in a stair-step pattern along the mortar, and that pattern usually points to settlement or soil pressure. The stair-step crack guide covers it. Crack injection kits are made for poured concrete, not hollow block, so a leaking block wall needs a different fix.

Is a vertical crack worse than a horizontal one?

No. A horizontal crack is usually the more serious of the two. Vertical cracks mostly come from shrinkage or settling, while a horizontal crack in a basement wall usually means soil is pushing the wall in.

The horizontal crack guide explains why and how to check a wall for bowing.

What should you do about a vertical crack in your foundation?

Measure it, check the edges, and decide whether it’s a watch-and-seal crack or an engineer crack. A five-minute check now tells you which. Then deal with any leak.

1. Measure the width

   Measure at the widest point with a crack gauge or a set of feeler gauges. The width guide shows which widths matter.

2. Compare top and bottom

   Measure near the top of the crack and near the floor. A crack that’s clearly wider at the top is the settlement shape.

3. Check the edges

   Run a straightedge or your hand across the crack. The two faces should be flush, with no step.

4. Look above and outside

   Check the drywall, siding or brick directly above the crack and the floor at its base. A crack that continues past the foundation is more likely settlement.

5. Mark it and date it

   Pencil a short line across each end and across the widest point, write the date and width next to it, and take a photo. The crack monitoring guide shows how to keep a log.

If the crack is thin, even, flush and stable, it’s a shrinkage crack. You can leave a dry one alone or seal it, and you should seal one that leaks.

How do you fix a vertical crack in a foundation wall?

Inject it from inside with polyurethane foam or epoxy. Injection fills the crack through the full thickness of the wall, so water can’t follow it in. It’s a normal DIY job for a stable crack under 1/4 inch in a poured wall.

Fix the water outside first. The NRMCA says the drainage around the structure should be checked and corrected (opens in a new tab) before repairing leaking cracks, and recommends a slope of 1/2 to 1 inch per foot for the first 8 to 10 feet from the house. Clear gutters and extend downspouts too.

Polyurethane foam is the usual pick for a leaking or damp crack because it reacts with water and stays flexible. Epoxy bonds the two sides together, but it needs a dry crack. The epoxy vs polyurethane comparison explains when each one fits.

Skip the hydraulic cement and caulk smeared over the surface. A surface patch only covers the inside face, so water still travels through the crack behind it and pushes the patch off.

The 10 ft kit is sized for one crack up to 10 feet long; measure yours before you order. For the full job, see the foundation crack injection guide. If water is already coming through, start with the leaking crack guide.