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Is a concrete crack from shrinkage or foundation movement?

Reviewed by Preston, Oklahoma foundation repair consultant ยท Updated 2026-10-14

In short: Many cracks in concrete and finishes are caused by the materials themselves shrinking as they dry or expanding and contracting with temperature, not by the foundation moving. Many of them appear early in a building's life and are usually cosmetic. A floor elevation survey and the crack pattern are what separate them from cracks caused by real foundation movement.

Why do materials crack on their own?

Concrete changes volume as its moisture and temperature change 1. As freshly placed concrete dries, it shrinks; as the seasons change, it expands and contracts. When that movement is restrained, for example by a footing, a wall or the ground, the concrete cracks 13. Concrete industry guidance states that cracks form when designs and construction do not allow for these movements 1.

These are sometimes called "mimic" cracks because they can look like signs of foundation movement even though the foundation has not shifted.

Common types

Type What it looks like Cause
Drying shrinkage cracks Random cracks in slabs, often appearing early Concrete shrinking as it dries while restrained 1
Crazing Fine, shallow surface cracks in a roughly hexagonal pattern, up to about 1.5 inches across Shrinkage of a paste-rich top layer 2
Corner cracks in basement walls Diagonal cracks from window and door corners Drying shrinkage 3
Thermal cracks Cracks tied to temperature swings Expansion and contraction under restraint 13

Crazing is rarely deeper than about 1/8 inch, usually appears by the day after placement or within the first week, and does not affect structural integrity 2.

How is concrete detailed to control cracking?

Concrete slabs are given contraction joints, grooves that create a planned weak line so the slab cracks there instead of randomly. Industry guidance calls for grooves about one-quarter to one-third of the slab thickness, spaced 24 to 36 times the slab thickness, with a maximum spacing of about 15 feet often recommended and panels kept nearly square 1. Isolation joints separate slabs from walls, columns and footings where movement may be restrained 1.

Most cracking traces to design and construction factors such as missing or poorly placed joints, poor subgrade preparation, too much water in the mix, improper finishing and inadequate curing 1. Random early-age cracks are unsightly but rarely affect the structural integrity or service life of concrete 1.

When is a crack more than cosmetic?

The concrete industry states that cracking is not necessarily a sign of poor materials, poor workmanship or a structural problem 3. For basement walls, typical warranties call for repair when cracks leak, show measurable vertical displacement or exceed 1/8 inch (3 mm) in width, and cracks that continue widening call for professional evaluation 3.

The Foundation Performance Association classifies distress as architectural, functional or structural, and notes that separations in drywall and stucco typically become noticeable at about 0.02 inch 4. Texas engineering guidelines add that signs such as cracked drywall or racked door frames do not necessarily mean a foundation is performing inadequately 5.

Checking for actual movement

Cracks alone do not prove the foundation moved. Without a baseline elevation survey, movement cannot be determined accurately, and most residential slabs are built only to within about 1 inch of level 4. Repeated surveys over months or years show whether the foundation's shape is changing 5. See elevation surveys and the distress pattern library.

What are the signs of shrinkage or thermal cracking?

Compare these with movement-related patterns such as stair-step brick cracks wider at the top, which are associated with perimeter drying settlement.

How are shrinkage cracks typically addressed?

Where the foundation is sound, the cracks are treated as finish repairs. Texas guidelines note that an owner may choose periodic cosmetic repairs and door adjustments rather than structural work 5. See cosmetic repair only.

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Common questions

Are hairline cracks in a new slab a foundation problem?

Not necessarily. Concrete changes volume as it dries and as temperature changes, and random early-age cracks rarely affect structural integrity or service life. Industry guidance states that cracking is not necessarily a sign of poor materials, workmanship or a structural problem.

What is crazing on concrete?

Crazing is a pattern of fine, shallow surface cracks, usually no deeper than about 1/8 inch, that form roughly hexagonal shapes. It typically appears within the first days after placement and does not affect structural integrity.

When does a basement wall crack need repair?

Typical warranties call for repair when a crack leaks, shows measurable vertical displacement or is wider than 1/8 inch. Cracks that keep widening over time call for professional evaluation.

How can I tell a shrinkage crack from a movement crack?

Shrinkage cracks tend to be fine, appear early in a building's life and do not come with changes in floor level. A floor elevation survey, especially compared with a baseline, shows whether the foundation has actually moved.

Sources

  1. CIP 4 - Cracking Concrete Surfaces National Ready Mixed Concrete Association
  2. CIP 3 - Crazing Concrete Surfaces National Ready Mixed Concrete Association
  3. CIP 7 - Cracks in Residential Basement Walls National Ready Mixed Concrete Association
  4. Guidelines for the Evaluation of Foundation Movement for Residential and Other Low-Rise Buildings (FPA-SC-13-1) Foundation Performance Association
  5. Guidelines for the Evaluation and Repair of Residential Foundations, Version 3 American Society of Civil Engineers, Texas Section

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