Is that Crack Harmless – or Dangerous? (Video)

“Greg Batista here, your friendly neighborhood engineer to answer your questions.

Spartacus4949 asks: How do you tell if a crack is cosmetic or serious?

Not all cracks are created equal. Hairline cracks in plaster or stucco are usually harmless — often caused by drying or minor building movement. But cracks in structural members like beams, slabs, or columns are a red flag. If you see cracks wider than the thickness of a credit card, or if you notice rust stains, water intrusion, or misalignment, that’s a strong indicator the problem goes deeper.

According to the American Concrete Institute, cracks in exposed concrete wider than 0.012–0.016 inches (0.3–0.4 mm) require evaluation, especially in coastal environments. Why? Because South Florida’s salt-laden air accelerates corrosion once it finds a path inside. And history shows what happens when cracks are ignored. The post-Surfside engineering reviews emphasized how unnoticed deterioration can silently progress until it’s too late.

When in doubt, bring in a licensed engineer. A small professional evaluation could prevent costly repairs — or save lives.

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Authoritative references: American Concrete Institute (ACI 224R – Control of Cracking in Concrete Structures); Florida Building Code HVHZ coastal exposure provisions; NIST Surfside Collapse Investigation Preliminary Findings.

The author, Greg Batista, PE, CGC, SI is owner of G. Batista Engineering & Construction and is a nationally-recognized engineer and contractor with more than 35 years of experience and offices in Fort Lauderdale, Florida.