Static field route #19603

What do I do when duct hits a rated wall at a 45-degree angle and the fire damper cannot sit square?

Fire/Smoke Dampers, Access Doors & Rated Assemblies🚨 STOP / VERIFYField answer expansion

📖 Verified core answer

Do not angle a fire/smoke damper through a rated wall unless the listed assembly specifically allows it. Square the duct to the wall with approved fittings before the damper sleeve.

Open in Field Rescue Open category

Field verification checklist

Confirm the wall rating and damper type.
Check manufacturer installation instructions for allowed orientation.
Verify sleeve is square to the wall plane.
Lay out upstream elbows/offsets to enter perpendicular if required.
Do not cover until access, sleeve, angles, and firestop are accepted.

Ask foreman

The duct approaches the rated wall at a 45 and the damper will not sit square in the sleeve. I stopped before cutting/setting it. Do you want an upstream offset to square the duct to the wall or a detailer RFI?

Text to foreman

Route options

A Correct it only if the fix is within your assignment and approved method.

B Hold and document if it affects pressure class, listed assembly, material spec, support load path, fire barrier, equipment, TAB, or another trade.

C Bring the foreman/detailer the location, what you checked, and what decision you need before sealing, testing, cover, or startup.

Do not do this

Do not install a fire/smoke damper cocked at an angle through a rated wall because the duct line came in crooked.

Why this matters

A misoriented damper can fail inspection or fail to close correctly in a life-safety event.

Final verification

Use this as field training guidance. Final direction still comes from the foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, pressure/material schedule, and AHJ/code requirements.

Search helpers: fire damper 45 angle rated wall FSD sleeve square perpendicular UL listed assembly