How to Tell Fiberglass Cracks From Gelcoat Crazing on Your RV, Step by Step

Here is the quick test. If the lines are shallow, weblike, and you cannot feel them with a fingernail, that is gelcoat crazing, a surface issue. If your nail catches in the line or it runs single-file from a stress point, the fiberglass underneath is likely involved, and that is a structural repair, not a cosmetic one.

Step one: look at the pattern

Crazing shows up as a spidery network of fine lines, often across a broad area that flexes or bakes in the sun. A structural crack is usually a single line, sometimes radiating from a corner, a fixture, or an impact point.

Step two: use your fingernail

Drag a nail across the line. Crazing sits on the surface and feels smooth. A real crack has depth and will catch the nail edge.

Step three: check what is behind it

• Cracks at a slide corner or window corner suggest flex or stress
• Lines that appear after an impact point to a fiberglass fracture
• Broad hazy webbing on a flat panel is usually just gelcoat
• A soft or spongy feel around the crack means water and delamination

Why does the difference matter for the repair?

Crazing can often be sanded and refinished. A structural fiberglass crack has to be ground out, backed, rebuilt with laminate, and only then refinished, or it comes right back.

Refinishing over a real crack is the most common shortcut we undo. It looks fine for a season, then the line telegraphs back through the new gelcoat.

When should you stop guessing and bring it in?

If the nail catches, if the area feels soft, or if the line sits at a stress corner, let a shop map it. Some cracks look minor from outside and hide a spreading fracture beneath the skin.

Not sure if it is crazing or a crack? OCRV Center handles both at our Yorba Linda shop, and Mission Viejo owners drive up so we can tell the surface issues from the structural ones before the repair starts.