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Normal foundation cracks: which ones are expected?

Normal foundation cracks are thin cracks that form as concrete dries and shrinks, usually within days to weeks of the pour.

Updated August 16, 2026

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Written by HyreFoundation Research Desk Primary-source research and fact checking

The short answer

Normal foundation cracks are thin cracks that form as concrete dries and shrinks, usually within days to weeks of the pour.

They tend to be vertical or slightly angled, hairline to about 1 mm wide, and stay the same width over time. In the damage scale engineers use, cracks up to about 5 mm are slight.

Wider cracks, growing cracks, horizontal cracks and those with movement signs deserve an engineer.

Key takeaways

Concrete shrinks as it dries and cracks when restrained; NRMCA says this shows within days to weeks

Normal: thin, vertical or slightly angled, stable

Engineers’ damage scale puts cracks up to about 5 mm in the slight range

Not normal: horizontal cracks in basement walls, stair-step cracks with bowing, cracks that keep widening

Measure the same spot monthly with the crack log

When a crack is not normal

A horizontal crack in a basement wall, especially with bowing

Stair-step cracks in block or brick that keep growing

Width about 5 mm or more, or one side offset from the other

A crack that grows month to month

Sudden new cracks with doors jamming or floors sagging: call a structural engineer promptly

Why concrete cracks at all

NRMCA: "When concrete dries, the moisture loss from its fine pores results in shrinkage." When the subgrade or structure restrains that shrinkage, tension builds and the concrete cracks

ACI 224R: shrinkage and restraint "develop tensile stresses within the concrete" and "cracking will often occur."

That is why control joints exist: to make cracks form in straight, planned lines

A crack from shrinkage does not mean the foundation is moving

A crack that changes over time might.

Normal against worth a call

Option	What it means for you
Direction	Vertical or slightly angled, often near corners or windows. Worth a call: horizontal in a basement wall, or stair-step with bowing.
Width	Hairline to about 1 mm. Worth a call: about 5 mm and up.
Change	Same width month to month. Worth a call: steadily wider or longer.
Other signs	None. Worth a call: sticking doors, sloping floors, a wall moving inward.

What to ask before you sign

Has the crack changed width since you first measured it?

Is one side offset from the other?

Is there water through it?

Are there other signs, like doors or floors?

The full checklist is on choosing a foundation contractor.

Where this goes wrong

Sealing before measuring

Sealant hides the change you need to see.

Trusting one photo

A single photo cannot show movement. Two dated readings can.

Calling a repair company to diagnose

Their inspection is a sales visit. An engineer you hire sells no repair.

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Questions

Are foundation cracks normal?

Many are. Concrete shrinks as it dries and almost always cracks somewhere. Thin, stable cracks are usually not structural.

What size foundation crack is a concern?

About 5 mm and wider, or any crack that keeps widening. The engineering damage scale moves from slight to moderate around there.

Are vertical foundation cracks normal?

Thin vertical cracks are the most common shrinkage cracks. They may still leak and can be sealed for water.

Are horizontal foundation cracks normal?

Not in a basement wall. They often mark soil pressure and should be seen by an engineer.

How do I know if a crack is getting worse?

Mark the spot and measure monthly. The crack log works out the change per month.

Written and audited by

HyreFoundation Research Desk

Primary-source research and fact checking

We read the model building code, the federal soil and moisture guidance and the insurer position ourselves, and we publish each figure with the document it came from and the date we retrieved it.

Where a number cannot be traced to a primary source, we say so instead of printing it. HyreFoundation does not inspect, engineer or repair foundations. Authorship is organizational: this desk, not a named persona.

40: pages published on this site
12: free tools, each showing its assumptions
0: foundation repairs we perform or sell
0: paid placements or rankings

How this desk works

Primary sources only. Code statements come from the International Residential Code, Chapter 4, as the model code. Soil statements come from USDA and USGS. Insurance statements come from the policy language and the Insurance Information Institute. We open the source rather than cite a blog that cites it.
The code is a model, and adoption is local. Your jurisdiction adopts an edition and amends it, and foundation chapters are amended more than most because frost depth and soil are local facts. Every code figure says so.
We hold no job data. We have no dataset of bids, pier counts or invoices, so no page claims an average from one. Calculators show the arithmetic and the inputs they assumed, and label the result as an estimate.
We do not diagnose your house. A crack guide can tell you which pattern to measure and when to call a structural engineer. It cannot tell you whether your foundation is failing. An engineer on site does that work.
We do not repair foundations, and we take no payment for placement, ranking or a favorable mention. Nobody buys a position on this site.

Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold. Our editorial policy sets out how we source, date and correct what we publish.

Sources & retrieval dates

TIP 17, Drying Shrinkage of Concrete , National Ready Mixed Concrete Association Retrieved Checked October 26, 2026.

ACI 224R-01, Control of Cracking in Concrete Structures, chapter 3 , American Concrete Institute Retrieved Checked October 26, 2026.

Mair, Taylor and Burland (1996), Table 1: classification of visible damage by crack width , International Society for Soil Mechanics and Geotechnical Engineering Retrieved Checked October 26, 2026.

Guidelines for the Evaluation and Repair of Residential Foundations, Version 3 (2022): levels of investigation A, B and C , ASCE Texas Section Retrieved Checked October 26, 2026.

Information on this page is general and varies with soil, climate, foundation type, building code, insurance policy and circumstance.

It is not engineering, insurance or legal advice, and no page can tell you whether your house has a structural problem: that needs a licensed professional on site.

HyreFoundation is an independent foundation resource, not a repair contractor or an engineering firm, and does not perform, supervise or warrant foundation work.