Concrete Slab Cracks: When to Worry, When to Ignore, When to Tear Out
A field-tested triage guide for every kind of slab crack — hairline, shrinkage, structural, settlement — with the width gauges and decision points that matter.
Five crack types, plain English
Plastic shrinkage: thin, short, random — appears within hours of placement. Cosmetic.
Drying shrinkage: longer, straighter, often along control-joint lines. Cosmetic if under 1/16 inch.
Settlement cracks: stair-step pattern in CMU walls, parallel-line cracks in slabs. Structural — investigate.
Structural overload cracks: wide (over 1/8 inch), through-thickness, often along beam lines or column lines. Get an engineer. See repair vs replace.
Map / pattern cracking: surface alligator pattern from alkali-silica reaction or poor curing. Surface-deep; evaluate before resurfacing.
The 1/16 / 1/8 / 1/4 rule
Under 1/16" (a credit card edge): monitor. Most are cosmetic.
1/16" to 1/8": seal with polyurethane to prevent water intrusion. Document with photos and a date.
Over 1/8": engaging a structural engineer is cheaper than guessing wrong.
Over 1/4" or any displacement (one side higher than the other): stop using the slab for load and get help today.
Repair options by severity
Epoxy injection: structural rejoin for narrow stable cracks. $20–$40 per linear foot.
Polyurethane sealant: flexible joint for moving cracks. $8–$15 per linear foot.
Slab jacking / foam lift: corrects settlement under intact slabs. $5–$25 per sq ft of slab area.
Full removal and re-pour: when the substrate or rebar is gone. Bedrock will core-test before quoting.
Frequently asked questions
No — control joints are designed to crack. That's their job. Seal them and move on.
Sealant prevents water intrusion and freeze-thaw expansion but won't stop structural movement. Address the cause.
Stable cracks don't change in 6 months. If a crack widens between photos taken months apart, get an engineer.
Get a free quote from Bedrock.
Residential and commercial. Licensed, bonded, insured.