Fire damper omission and a disputed change order
A mechanical contractor is installing a new 12 x 8 in. galvanized supply duct in a 4-story office building. The duct passes through a 2-hour rated corridor wall and then through a 1-hour rated ceiling assembly. The signed proposal says 'replace existing duct like-for-like; all work to meet code.' The existing duct has no fire damper at the 2-hour wall, and the penetration is sealed with ordinary latex caulk. The owner's representative says the missing damper was 'grandfathered' and refuses a change order. The contractor has already cut the opening 2 in. larger to fit a volume damper and has not obtained a permit. The building inspector is scheduled in two days.
1. What code and life-safety issues must be resolved before the inspection, and who should pay?
Read the worked answer
The 2-hour rated corridor wall is a fire-resistance-rated assembly. A duct penetration generally requires a listed fire damper or a listed fire-rated duct assembly, and the annular space must be sealed with a listed firestop system, not latex caulk. The 1-hour ceiling penetration may also require a damper depending on the assembly and duct type. A volume damper is not a substitute for a fire damper.
'Grandfathered' does not automatically apply when the duct is being replaced and the opening is being altered. The contractor should stop work, obtain the required permit, and ask the authority having jurisdiction to confirm the required assembly. The contract says the work must meet code, so the owner should pay for the code-required correction unless the contract clearly excluded existing noncompliant conditions. The contractor should document the existing condition with photos and a written request for information before proceeding.
2. How would you select and install the fire damper in the 12 x 8 duct? Include access, sleeve, and firestopping.
Read the worked answer
Select a listed fire damper with a rating equal to or greater than the required fire-resistance rating of the wall, and size it for the 12 x 8 duct and the required airflow. Install it in a listed sleeve or frame in the rated assembly, with the damper blade and position indicator accessible through a listed access panel. The damper must not be blocked by the volume damper or duct insulation.
Connect the duct to the damper with the manufacturer's listed breakaway or breakaway-style connections so the duct can collapse without pulling the damper out of the wall. Seal the annular space with the listed firestop system for the wall type and penetration size. Do not use latex caulk, expanding foam unless listed, or ordinary duct sealant as a firestop. The installation must match the listed assembly, including damper orientation, clearance, and retaining angles, and it must be inspectable before the ceiling is closed.
3. What should the contractor do about the enlarged opening and the inspector?
Read the worked answer
The contractor should stop work, admit the opening was enlarged without approval, and not cover it. The enlarged opening may exceed the listed firestop or damper assembly, so it needs an approved repair detail from the firestop manufacturer or a licensed engineer, and the AHJ must approve it. The contractor should apply for the permit immediately, document the sequence, and ask for a short inspection delay rather than hide the condition.
Before the inspection, the contractor should have the listed damper, sleeve, access panel, and firestop system installed per the listing, with product data sheets on site. The volume damper should be relocated or removed if it conflicts with the fire damper. The contractor should also send a written change-order request to the owner explaining the code requirement and the cost. If the owner refuses, the contractor should not proceed with a noncompliant installation and should seek the AHJ's direction in writing.