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bbacho
Duct Work
bbacho

I have a new 2 story addition behind my garage. Above my garage is the master bedroom. The joists under my bedroom are 2x8. I need to move a supply duct over one bay that feeds my bedroom. Do you think it would be feasible to just use a 90 degree elbow to jump to the next bay or would I weaken the one joist too much putting a 6 inch hole in it. My ducts are 6 inch. Any other thoughts would be appreciated.

dj1
Re: Duct Work
dj1

The max hole size allowed in a 2x8 joist is 2-3/8".

ed21
Re: Duct Work
ed21

7 1/2" - 6" = 1 1/2" / 2 = 3/4" of wood above and below duct. Might not be enough wood left to even nail into. Although I've seen plumbers that think that's plenty of wood left in a joist.
Building a supply bulkhead would allow you to take off ducts at any location.

keith3267
Re: Duct Work
keith3267

OK, this is a little out of the box but it might work. Get two floor vents that are 2x12 in size and 6" round at the other end. Then you just cut a 2x12 slot in the joist and connect and seal the 2x12 ends of the vents together at the slot. Then attach the 6" round ducts on the other ends.

Another way to do this is to box in the adjoining bays with 2x8. Each bay will have a box about 16" square. Caulk all the seams so that the box is airtight. Before sealing the bottom, drill a series of holes about 1.5" to 2" in diameter through the joist between the boxes. If the vent to the room is above one of the boxes, then just cut the opening in the floor for it. Make a 6" hole in the end of the box for the other bay and terminate the duct at it.

Seal the bottom of both boxes with a piece of plywood that is caulked to prevent any air leakage.

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