Fireblocking around flexible HVAC ducts


Old 01-18-05, 12:59 PM
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Fireblocking around flexible HVAC ducts

Any suggestions on how to fireblock around flexible ducting? Here is my situation.

My basement has it's own forced air heatpump system. The HVAC contractor ran a number of small diameter (6-8") flexible ducts to each of the registers. Since the ducts run perpendicular to the ceiling joist, they are hung with straps below the joists. I am going to put a suspended ceiling just below the ducts.

I framed a utility room around the air handler. The ducts are perpendicular to the utility room wall and run just under the top plate. I put blocking between the studs just below the ducts. I can drywall up to the blocking beneath the duct which will be the approximate height of the ceiling.

My understanding is that I need fireblocking between the utility room and the space above the syspended ceiling. I need to figure out how to fill the voids between the round ducts and the square opening between the studs and blocking. Since the flex ducts crush and move easily, I am not sure what would work best. Thanks.
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Old 01-26-05, 09:03 PM
Join Date: Feb 2001
Location: massachusetts
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it seems it might be easiest to use 5/8 sheetrock up to the first floor deck. First remove the ducts. install the sheetrock. cut round openings/ pass through the flex ducts or cut the flexible ducts and pass through solid sections and connect ducts..

Last edited by StephenS; 01-26-05 at 09:06 PM. Reason: misread his name
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