Part of a Pittsburgh seam was not knocked down

A Pittsburgh seam has to be mechanically folded tight before it is sealed. If a section is left open, knock it down fully before mastic goes over it.

Stop if

• You can't leave a gap in a Pittsburgh seam. Grab the blocking hammer and knock that center section down completely flat over the pocket lip before you swipe it with bucket seal.

Watch out

• Do not smear mastic over an open seam and call it fixed.

Check

• Run your hand/eyes down the full seam length.
• Find any lip that is still standing proud.
• Support the duct body while peening the seam.
• Knock the raw edge flat over the pocket lip.
• Seal only after the mechanical seam is closed.

Steps

• Run your hand/eyes down the full seam length.
• Find any lip that is still standing proud.
• Support the duct body while peening the seam.
• Knock the raw edge flat over the pocket lip.
• Seal only after the mechanical seam is closed.

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