Are Foundation Cracks Normal? When to Worry and How to Tell

Are cracks in a foundation normal?

Yes. The concrete industry’s own guide says plainly that some cracking is normal in concrete basement walls (opens in a new tab), and that a crack is not necessarily a sign of poor materials, bad work or a structural problem.

Concrete shrinks as it dries. The footing and the floor hold the wall in place, so the wall cracks to relieve the strain. That usually happens in the first year, and the crack stays about the same size afterward.

A normal shrinkage crack has a recognizable profile. Pillar To Post’s inspectors describe it as vertical, usually under 1/8 inch wide, and in the middle third of the wall (opens in a new tab), and it stays in the foundation instead of continuing up through the house.

Diagonal cracks running from the corners of basement windows are shrinkage too.

How wide is too wide for a foundation crack?

Under 1/8 inch is normal. From 1/8 to 1/4 inch deserves a closer look and a few months of watching. Over 1/4 inch, get an engineer’s opinion.

Those lines come from the concrete and home building industries. The NRMCA says a typical new-home warranty requires repair of a basement wall crack wider than 1/8 inch (opens in a new tab), and NAHB guidelines set the correction line for basement walls at 1/4 inch (opens in a new tab).

Inspectors don’t treat these numbers as hard rules. An NAHB presentation by a warranty company engineer says there is no absolute universal standard for evaluating cracks (opens in a new tab). Width is one sign, weighed with direction, offset and whether the crack is growing.

What is the nickel test for foundation cracks?

The nickel test means sliding a coin’s edge into the crack to judge its width. It’s a rough gauge at best: a coin isn’t a measuring tool, so it can’t tell you which side of the 1/16, 1/8 or 1/4 inch lines a crack falls on.

Use a ruler or a crack width card at the widest point of the crack instead. A card reads the width directly, and you can write the number down to compare later. No coin is anywhere near 1/4 inch thick, so a coin can’t tell you when to call an engineer.

A coin only measures width. It tells you nothing about whether one side of the crack has moved out past the other, which matters more.

When should you worry about a foundation crack?

Worry about a crack that shows any of the signs below, whatever its width. Knowing when to worry about foundation cracks is mostly about direction, offset and growth, because these point to a wall or footing that has moved. They need a structural engineer before any repair, since sealing a moving crack just hides it for a while.

• It runs horizontally. A horizontal crack in a basement wall usually means soil pressure is pushing the wall in. The horizontal crack guide explains why.
• It stair-steps through a block wall. These follow the mortar joints and point to settlement or soil pressure.
• The edges don’t line up. Run your hand across it. If one side sticks out past the other, Pillar To Post calls that a significant structural concern (opens in a new tab).
• The wall bows or leans. ASHI’s Feiza says any movement over 1/2 inch signals a potentially serious problem (opens in a new tab), and recommends checking with a 4-foot or longer level, a laser level or a plumb bob. See bowing basement walls.
• It’s wider than 1/4 inch, or getting wider. The NRMCA’s advice is to seek professional advice for active cracks that are widening (opens in a new tab).
• It came back after a repair. A settlement crack that reopens after it was fixed can mean the movement hasn’t stopped.
• There are several kinds at once. Feiza writes that a combination of cracks needs a professional review (opens in a new tab).
• Doors and windows upstairs start sticking. The NAHB presentation lists inoperable doors and windows (opens in a new tab), floor tilt and vertical displacement among the signs of a structural crack.

An independent structural engineer looks at the crack without selling the repair. The engineer vs contractor guide explains who to call and what it costs.

How do you tell if a foundation crack is getting bigger?

Mark it, measure it and check it again over at least 90 days, then once more after the seasons change. A crack that stays the same width and length through that period is very likely stable. One that grows is active, and that’s an engineer call.

1. Mark both ends

   Draw a short pencil line across each end of the crack and write the date beside it. If the crack runs past the line, it’s getting longer.

2. Measure the widest point

   Hold a ruler or tape across the widest spot, mark that spot on the wall, and photograph the ruler in place. Always measure at the same mark.

3. Check every 30 days

   Re-measure and photograph on the same spot every month for at least 3 months. Write the reading, the date and the weather in a log.

4. Check again after the season changes

   Cracks can open and close with soil moisture and frost. Feiza notes that horizontal cracks often will change seasonally (opens in a new tab), so a spring reading and a fall reading tell you more than three readings in one season.

The 90-day window is a practical starting point, not a standard from any one source. A crack gauge makes small changes easier to read; the crack monitoring guide shows how to set one up.

What should you do about a normal foundation crack?

If it’s dry and stable, you can leave it. If it leaks, seal it. A typical new-home warranty treats a leaking crack as one that needs repair (opens in a new tab) even when it’s narrow.

Check the outside first. The NRMCA says to check the drainage around the house before repairing a leaking crack. Make sure downspouts discharge away from the wall and the soil slopes away from the foundation.

A thin vertical or diagonal crack in a poured wall is a reasonable DIY repair. The foundation crack repair guide covers the options, and leaking basement wall cracks covers sealing one that lets water in. For every crack type side by side, see the foundation cracks hub.