Aluminum Duct Deforms While Fasteners Are Started

Fast answer

Stop tightening and restore the pieces to their intended shape before continuing. Verify the approved connector, fastener, hole size, spacing, backing, and tightening method for the aluminum assembly.

What to check

1. Check whether the duct is out of round, oil-canned, or torn.
2. Inspect predrilled holes and connector fit.
3. Support the joint evenly.
4. Confirm whether the damaged piece remains acceptable.

Do not

Do not keep driving fasteners until the metal pulls together or substitute a larger fastener without approval.

Ask the foreman

“The aluminum joint starts to pucker as the fasteners tighten even though the ends are aligned. I checked the connector fit and support. Do you want the hole pattern or joint method reviewed before we continue?”

Why it matters

Aluminum can distort or tear before the installer feels the resistance expected from galvanized steel.