TinnerFlow™2nd YearDampersRED · Stop / Verify
The rough wall framing opening must be larger than the damper sleeve. The general standard rule of thumb is leaving \frac{1}{8} inch of clearance per linear foot of damper width and height, or a strict minimum of \frac{1}{2} inch total clearance gap around the entire sleeve perimeter, unless specified otherwise by the UL installation listing sheet.
The rough wall framing opening must be larger than the damper sleeve. The general standard rule of thumb is leaving \frac{1}{8} inch of clearance per linear foot of damper width and height, or a strict minimum of \frac{1}{2} inch total clearance gap around the entire sleeve perimeter, unless specified otherwise by the UL installation listing sheet.
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.