TinnerFlow™2nd YearPenetrations / SleevesYELLOW · Check First
Raw masonry can chew into duct over time. Use an approved sleeve/trim/firestop/acoustical detail so the duct does not rub concrete and the penetration can be sealed correctly.
Running thin duct skin directly through a rough block wall may look fine on day one, but vibration and sharp masonry edges can wear holes, damage coatings, and create leaks.
The recovery is to verify the wall type/rating and install a proper sleeve or protection detail before final seal/trim. The gap treatment depends on whether the wall is rated, exterior, acoustic, smoke, or ordinary partition.
Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.