Every Brick Building Has Cracks — The Question Is Which Ones Matter

If you manage brick buildings long enough, you learn that cracks are not rare. Masonry moves — it expands in heat, contracts in cold, settles, and responds to the building behind it. A certain amount of cracking is simply what brick does over a lifetime. So the useful skill isn't spotting cracks. It's telling the difference between the ones that are cosmetic and the ones that are warning you about something serious.

Get that judgment wrong in either direction and it costs you. Treat every hairline crack as an emergency and you waste money chasing nothing. Wave off a structural crack as "just the building settling" and you can let a real problem — a failing lintel, a moving foundation, water working into the wall — run until the repair is many times larger. This is a guide to reading a brick crack the way a mason does: by its width, its direction, its location, and whether it's still moving.

Width: How Big Is It?

Width is the first and bluntest measure.

Hairline cracks — thinner than about 1/16 of an inch, roughly the width of a sheet of paper or two. On their own, these are usually minor. They often run in the mortar joints and frequently come from normal thermal movement and shrinkage.
Moderate cracks — somewhere between 1/16 and about 1/4 inch. These deserve attention. They may still be benign, but at this width they're letting water in and they can be a sign of ongoing movement.
Wide cracks — wider than about 1/4 inch, especially if the two sides don't line up evenly or you can see into the wall. Treat these as a real concern until a professional says otherwise.

Width alone isn't the whole story, though. A thin crack in the wrong place and direction can matter more than a wider one somewhere harmless. That's why direction is the next thing to read.

Direction: Which Way Is It Running?

The direction of a crack tells you a lot about its cause.

Stair-step cracks

A crack that climbs the wall by following the mortar joints — over, up, over, up, in a staircase pattern — is one of the most common and most telling. Stair-step cracking usually points to differential movement: one part of the building moving relative to another. Common causes are foundation settlement, a failing lintel below, or soil movement. Stair-stepping near the corners of a building or radiating from the corners of windows and doors is worth taking seriously.

Horizontal cracks

A long horizontal crack is the one to respect the most. Horizontal cracking — especially running along a floor line, or low on a foundation wall — can signal serious pressure on the wall: a rusting shelf angle or lintel jacking the brick, soil pressure pushing a foundation in, or a wall beginning to bow. Horizontal cracks are more often structural than cosmetic and generally warrant prompt professional assessment.

Vertical cracks

A vertical crack running straight up through brick and joints alike can come from thermal expansion (often where an expansion joint is missing or has failed) or from settlement. Vertical cracks vary widely in seriousness depending on width and whether they're moving, but a vertical crack running through the brick units rather than around them means the force was strong enough to break brick, not just open joints — which is more significant.

Location: Where Is the Crack?

The same crack means different things in different places.

At the corners of windows and doors: openings are weak points where stress concentrates. Cracking here often points to a lintel problem above or settlement below.
Along a floor line on a taller building: suspect a shelf angle — rusting steel or a blocked expansion joint lifting the brick.
At building corners: a frequent location for settlement-driven stair-step cracking.
Low on a foundation wall: horizontal cracking here can mean soil pressure and deserves prompt attention.
Following a straight line up a tall blank wall: often thermal movement looking for the expansion joint the wall doesn't have.

The Most Important Question: Is It Moving?

A crack that opened years ago and has been stable ever since is a very different thing from one that's actively widening. Movement is what separates a finished event from an ongoing problem.

You can watch a crack over time. Note its width against a reference (a coin, a ruler, a dated photo), and check it across seasons. Some seasonal opening and closing is normal — brick expands in summer and contracts in winter, so a thermal crack may breathe a little. What you're watching for is a crack that gets progressively wider and doesn't come back, or one that's clearly larger than it was a year ago. Steady, one-directional growth means something is still moving, and that's the signal to bring in a professional rather than keep watching.

A Simple Triage for Property Managers

When you find a crack, run it through four quick questions:

How wide? Hairline is usually minor; wider than a quarter-inch deserves a look.
Which direction? Horizontal is the most concerning; stair-step suggests movement; vertical depends.
Where? At openings, floor lines, corners, and foundations, cracks carry more meaning.
Is it growing? A stable crack is far less urgent than one that's actively widening.

If the answers point to "narrow, stable, in the joints, not at a sensitive spot," it's likely a maintenance item — repoint it to keep water out and keep an eye on it. If they point to "wide, horizontal or stair-step, at a lintel or floor line or foundation, and growing," that's a call to make now. And remember that even a cosmetic-looking crack is still an open door for water, which in a Chicago-area winter starts the freeze-thaw damage that turns small problems into big ones.

When in Doubt, Get It Read

Reading cracks well takes experience, and there's no shame in not being sure — the cost of guessing wrong runs in both directions. If a crack in one of your buildings has you wondering whether it's a budget note or a problem, have someone who repairs masonry for a living look at it.

Emerald Masonry LLC is a family-owned, licensed, bonded, and insured masonry contractor based in Palos Heights, with more than 40 years of experience diagnosing and repairing brick across Chicagoland. We'll tell you honestly whether a crack is cosmetic, a maintenance item, or a structural issue that needs attention — and what it will take to fix. Contact us for a free on-site assessment, or call (708) 288-1696.

Hairline Cracks vs. Structural Cracks in Brick — A Property Manager's Guide to What's Urgent