How do I know if my concrete crack is serious?

Cracks rated severity 1–2 are cosmetic and can be addressed with DIY crack filler. Cracks rated 3 need a professional assessment. Cracks rated 4–5 may indicate structural problems and require a contractor or structural engineer. Our analyzer gives you a severity score with every diagnosis.

What type of crack is in my concrete?

The six most common types are: shrinkage cracking (fine, map-pattern, cosmetic), structural cracking (wide, displaced edges), freeze-thaw spalling (surface flaking near edges), settlement cracking (one section lower than adjacent), alkali-silica reaction (web cracking with white gel residue), and corrosion-induced cracking (rust staining along crack lines). Upload a photo and our AI will classify it for you.

Is this crack analyzer accurate?

The analyzer uses Claude, a state-of-the-art AI vision model, trained to identify structural and cosmetic patterns in concrete. When the photo is ambiguous between two classifications, we always default to the higher severity — it is better to be over-cautious than to provide false reassurance. User feedback on diagnosis accuracy consistently rates above 70%.

Do I need a structural engineer for my concrete crack?

You need a structural engineer for cracks with visible displacement between edges (one side higher than the other), cracks wider than 1/4 inch, rust-brown staining along crack lines (indicating rebar corrosion), or any crack in a load-bearing structural element like a foundation wall, beam, or column.

How do I repair a concrete crack myself?

For severity 1–2 cosmetic cracks, use a polyurethane or epoxy crack filler for narrow cracks, or a concrete patching compound for wider surface damage. Clean the crack of debris, apply filler per the product instructions, allow to cure, then seal the surface. For anything rated severity 3 or higher, get a professional assessment before attempting repairs.

What causes concrete to crack?

Concrete cracks for several reasons: normal shrinkage as it cures (shrinkage cracking), freeze-thaw cycles that expand moisture within the concrete (spalling), soil movement beneath the slab (settlement), overload or impact (structural cracking), a chemical reaction between aggregate and cement paste (alkali-silica reaction), or corrosion of embedded steel reinforcement (corrosion-induced cracking).

How do I know if a concrete crack is structural or cosmetic?

A crack is structural if: one side is higher than the other (vertical displacement), it is wider than 1/4 inch, it runs through a load-bearing element like a foundation wall or beam, or it shows active movement. Cosmetic cracks are shallow, hairline-width, have no displacement, and do not worsen over time. When in doubt, upload a photo to the concrete crack analyzer for an instant classification.

When should I call a structural engineer versus a contractor for a concrete crack?

Call a structural engineer (not just a contractor) if: the crack is in a foundation wall, beam, column, or other load-bearing element; there is visible displacement between crack edges; the crack is wider than 1/4 inch; or you see rust staining indicating rebar corrosion. A contractor is sufficient for severity 3 cracks in non-structural flatwork like driveways, patios, or sidewalks.

How wide does a concrete crack need to be before it requires repair?

Cracks under 1/16 inch (hairline) are typically cosmetic and can be monitored or sealed. Cracks between 1/16 and 1/4 inch warrant professional assessment. Any crack wider than 1/4 inch — especially with displacement — requires immediate professional evaluation. Width alone does not determine severity; displacement and location matter more.

What are the most common types of concrete cracks?

The six most common types are: shrinkage cracks (fine map-pattern lines during curing), structural cracks (wide cracks with vertical displacement), freeze-thaw spalling (surface flaking), settlement cracks (one section lower than adjacent), alkali-silica reaction (web cracking with white gel residue at edges), and corrosion-induced cracking (rust staining along linear cracks). Each has a distinct cause and repair approach.

What causes concrete to crack shortly after it is poured?

New concrete cracks primarily due to plastic shrinkage during curing — if the mix has too much water, dries too fast in hot or windy conditions, or lacks control joints at proper intervals (every 8–12 feet). These cracks are usually cosmetic. Cracks forming weeks later often indicate improper subgrade compaction or premature loading.

Can concrete cracks be repaired without replacing the slab?

In most cases, yes. Severity 1–2 cracks can be filled with polyurethane or epoxy crack filler as a DIY repair. Severity 3 cracks may require professional resurfacing or mudjacking. Severity 4–5 structural cracks may require partial or full slab replacement depending on the structural element and extent of damage.

How do I identify alkali-silica reaction in concrete?

ASR presents as a dense web of cracks covering the entire surface with white or pale gel visible at crack edges — the expansion product of the silica-alkali reaction. ASR progresses over years and has no DIY fix; affected structural elements require engineering evaluation. Definitively confirmed by petrographic analysis of a concrete core sample.

Is there a free tool to diagnose a concrete crack from a photo?

Yes. The SlabCalc Concrete Crack Analyzer accepts a photo upload and returns an instant AI diagnosis: failure mode classification (F1–F6), severity score (1–5), certainty percentage, and a repair recommendation. No sign-up required.

Concrete Crack
AnalyzerFREE

Photo in, diagnosis out — failure mode, severity, and what to do next.

Tap to upload or take a photo

Click to upload · drag & drop

JPEG · PNG · WebP · Max 10 MB

How it works

Take a photo

Close-up, good lighting, crack in frame.

AI diagnoses

Classifies failure mode in seconds.

Get your result

Severity score and repair guidance.

How It Works

Upload a photo

Take a clear, close-up photo of the damaged area in good lighting. The more detail visible, the more accurate the diagnosis.

AI analyzes the damage

Our AI examines crack width, pattern, displacement, staining, and surface texture against six known concrete failure modes.

Get your diagnosis

Receive a failure mode classification, severity score from 1–5, plain-language explanation, and a clear repair recommendation.

Six Failure Modes

Shrinkage Cracking

Fine, shallow cracks in a map pattern or running parallel. Uniform width under 1/16 inch with no displacement. The most common type — typically cosmetic.

Identify shrinkage cracks →

Structural Cracking

Wide cracks (over 1/4 inch) running vertically or diagonally, often with one side visibly higher or lower than the other. Indicates overload or structural failure.

Identify structural cracks →

Freeze-Thaw Spalling

Surface flaking, pitting, or the top layer lifting away in scales. Most visible near slab edges. Caused by moisture freezing and expanding within the concrete.

Identify freeze-thaw spalling →

Settlement Cracking

One section of slab sits noticeably lower than the adjacent section. Crack runs along a joint line or diagonally from a corner. Caused by soil movement or voids beneath the slab.

Identify settlement cracks →

Alkali-Silica Reaction (ASR)

A web of cracks covering the entire surface, often with white gel residue visible at crack edges. Progressive damage — no DIY fix exists.

Identify alkali-silica reaction →

Corrosion-Induced Cracking

Linear cracks running parallel to the surface, with rust-brown staining along the crack line. Indicates corrosion of embedded steel reinforcement.

Identify corrosion-induced cracks →

Quick Reference

Failure Mode	Key Visual	Severity	Action
F1 Shrinkage Cracking	Fine map cracks, no displacement	1–2	DIY
F2 Structural Cracking	Wide crack, one side higher	3–5	Professional
F3 Freeze-Thaw Spalling	Surface flaking near edges	2–4	Professional
F4 Settlement Cracking	Step at joint, section lower	2–4	Professional
F5 Alkali-Silica Reaction (ASR)	Dense web cracking + white gel at edges	3–5	Engineer
F6 Corrosion-Induced Cracking	Rust-brown staining along crack	3–5	Engineer

Severity Guide

Severity 1–2

Cosmetic Damage

Surface-level cracks with no structural implication. DIY repair products are appropriate. Monitor for widening.

Severity 3

When to Call a Contractor

Cracks that exceed cosmetic thresholds but stop short of structural risk. Professional assessment required before repair.

Severity 4–5

When to Call a Structural Engineer

Structural risk indicators: displacement, width over 1/4 inch, rebar corrosion, or cracks in load-bearing elements.

View full severity guide →

Comparison Guides

Shrinkage vs. Structural Cracks

Side-by-side comparison table, 3-step diagnostic, and cost differences between the two most common crack categories.

Compare →

Related Resources

Guides

Repair & Troubleshooting

Step-by-step repair guides for every crack type →

Guides

How to Repair Concrete Cracks

Step-by-step repair for every crack type and severity →

Calculators

Concrete Slab Calculator

Estimate how much concrete a patch or repair section needs →

Accuracy & Limitations

This tool uses AI vision analysis to classify concrete damage from photos. Diagnosis accuracy depends on photo quality — clear, well-lit, close-up shots produce the most reliable results. When the image is ambiguous between two classifications, we default to the higher severity. This tool is designed to guide decisions, not replace a professional assessment. For any crack rated severity 4 or higher, consult a licensed structural engineer before taking action.

Frequently Asked Questions

Next Steps

Once you know what type of crack you have and how severe it is, plan your next move.

Calculator

Concrete Slab Calculator

Estimate materials for a replacement slab or patch →

Calculator

Footing Calculator

Size footings for foundation repairs or new pours →

Cost Guide

Foundation Cost Guide

Real pricing data for foundation work in your area →