Apprentice answer

Drywall crushes flex duct in a wall cavity

2nd YearFlex Duct, Boots, Grilles & DiffusersCheck first

Crushed flex is an airflow restriction, not a finish-detail inconvenience. Pull it out of the pinch point and use an approved rigid/alternate path that fits the wall cavity without choking the branch.

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Plain-English answer

Flex duct cannot deliver air if the core is flattened, kinked, or smashed behind drywall. A wall that physically crushes the duct is telling you the material/path is wrong.

The fix is usually to stop cover, expose the pinch, and change the branch path or material: rigid wall stack, oval/rectangular metal, different boot location, or approved alternate route. Do not fight drywall around a crushed flex and hope air makes it through.

Field checklist

Confirm where the flex is being pinched and whether drywall/framing is already installed.
Check branch size, diffuser/boot location, and whether rigid wall stack/oval/rectangular duct is specified or approved.
Check for access to replace the crushed section before the wall closes.
Look for excess flex length, tight bends, and strap/crush damage.
Take a photo of the pinch and ask before changing material or route.

Ask Foreman

The flex branch at [location] is being crushed by framing/drywall. I checked the boot and wall cavity. Do you want a rigid wall-stack/oval replacement, a reroute, or a different boot location before they close it?

Verify before acting

Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

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