Static field route #18915

What do I do when a Pittsburgh seam was not knocked down and is leaking?

Rectangular Duct Assembly: S-and-Drive✅ STANDARD FIELD CORRECTIONV189 answer-gap expansion

📖 Verified core answer

A Pittsburgh seam leak usually needs the mechanical seam completed first, then sealed. Do not try to fix an open pocket seam with mastic alone.

Open in Field Rescue Open category

Field verification checklist

Find the exact length of open or loose Pittsburgh seam.
Check whether the duct is already insulated, hung under tension, or connected to equipment that could be damaged by hammering.
Confirm you can close the seam without oil-canning the panel or deforming the fitting.
Finish the mechanical lock before applying approved sealant.
Recheck for whistle/leak after correction.

Ask foreman

The Pittsburgh seam at [location] was not knocked down for about [length]. I checked access and panel support. Do you want me to finish the seam and seal it, or replace/correct the section if it is damaged?

Text to foreman

Route options

AMake the field correction only if it is within your assignment and the approved method.

BHold and document the condition if the fix affects airflow, access, life safety, pressure class, rated assemblies, equipment, or another trade.

CBring the foreman/detailer the location, what you checked, and what decision you need before cover, startup, or rework.

Do not do this

Do not smear mastic over an open Pittsburgh pocket and call it sealed.

Why this matters

The seam is both a mechanical connection and a leak path. If it is not fully closed, it can whistle, leak, and fail pressure/TAB checks.

Verification basis

Approved drawings/specs, project coordination drawings, manufacturer instructions/submittals, shop standards, foreman/detailer direction, employer policy, and AHJ/code requirements.