Concrete Cracks: Which Ones Are Cosmetic and Which Need Attention

Cosmetic cracks

Hairline shrinkage cracks. Concrete shrinks as it cures, and small cracks (under 1/16 inch) appear on most slabs within the first year. Random pattern, no offset between the two sides — these are normal and rarely structural.

Control joint cracks. Control joints (the sawn lines in your driveway or basement floor) are designed to direct cracks. A crack along the joint is the system working.

Pay-attention cracks

Cracks wider than 1/4 inch. Even if there's no offset, a wider crack lets water in. Sealing prevents freeze-thaw damage.

Active cracks. A crack that's changing shape or width with seasons or load is signaling movement. Worth monitoring; possibly worth investigation.

Diagonal cracks emanating from corners. Often from foundation settlement at a corner. The corner is the most flexible point on the foundation; movement shows up there first.

Take-action cracks

Stair-step cracks in masonry walls. Following the mortar joints in a diagonal stair pattern, especially with width over 1/4 inch and offset between sides. Often indicates differential settlement.

Horizontal cracks in basement walls. Pressure from outside (saturated soil, frost heave). Can indicate the wall is bowing inward.

Cracks with offset. One side of the crack is higher or lower than the other. Differential movement is happening.

Cracks that are leaking water. Even small ones — water under pressure finding a path is a real problem.

What this means for you

A photograph and a measurement (width, length) of any concerning crack gives you a baseline. A second photo in six months tells you whether it's growing.

What contractors should know

Customers want to know whether to worry or not. Confidently classifying their crack — with reasoning — builds trust and ends 90% of "is my foundation broken?" questions.

Before you call anyone out

If you're not sure whether the work was done right, the cheapest first step isn't a contractor callback or a paid third-party inspection — it's a documented second opinion you can refer back to.

Supervisr's Concrete and Masonry QA model follows industry standards and guidelines set forth by ACI (318 / 332 concrete, 530 / TMS 402 masonry), NRMCA (Concrete in Practice series), NCMA (TEK notes), the Brick Industry Association (Tech Notes), and ASTM (C270 mortar). It can evaluate concrete and masonry photos for control joint spacing, reinforcement placement, cure documentation, brick veneer anchoring, weep placement, and mortar joint tooling. Upload photos of control joint pattern and timing, rebar coverage and spacing, weep hole presence and spacing, brick tie spacing, mortar joint profile, and you'll get a documented evaluation back in minutes with citations to the specific standards involved. It's the same checklist a careful inspector uses — applied to your photos, on your timeline.

For homeowners, that documentation is your conversation-starter with the contractor (or, if needed, your insurer or warranty carrier). For contractors, it's the third-party verification that closes the conversation cleanly.

About Supervisr

Supervisr is an AI quality-assurance platform for residential concrete and masonry work. It follows industry standards and guidelines set forth by ACI, NRMCA, NCMA, the Brick Industry Association, and ASTM, and evaluates concrete and masonry photos against those published references.