Elbow Boot Ceiling Joist Detail

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MindBender
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Joined: Fri Aug 19, 2016 4:59 pm

Elbow Boot Ceiling Joist Detail

Post by MindBender » Wed Aug 09, 2017 11:08 am

I have to install two 5 inch duct supplies in a joist bay area. I'm using the regular angled boots as pictured here http://imperialgroup.ca/round.cfm?c=109#496. One duct is going into a subfloor and the other is going to point down into what will be a drywall ceiling. I need help on the details on how the boot should be installed relative to the finish materials.

For the ceiling, I'm thinking I should build a frame around the boot and have it sticking out 1/2 inch (for drywall finish) - is this correct? Or am I supposed to allow extra so I can bend the flaps over the drywall or even below the drywall.

For the floor I plan to just flust the boot with the subfloor and nail sideways.

If you know a better way to install these, that would be awesome to hear about... I've seen sheet metal used to support them too - is that code?


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Aaron
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Location: St. Paul, MN

Re: Elbow Boot Ceiling Joist Detail

Post by Aaron » Wed Aug 09, 2017 11:30 am

You have the right ideas. You rough-in the boot on the ceiling so its sheet metal edge is flush with the drywall hole you cut out for it, or slightly below it, but by no more than a quarter inch or so. When the room is painted and finished, you attach a louver to it which is flush with the drywall which creates a nice finished appearance.

The floor one is basically the same thing. Nailing or screwing in the sides is totally the right thing to do, use galvanized roofing nails or normal construction screws. If you're making cutouts for the first time, drill some pilot holes at opposite corners of the rectangle of where the boot will protrude through the floor, and then measure from those holes upstairs so you can draw the rectangle and know exactly where to cut.

I highly recommend investing in an oscillating tool to make plunge cuts. They are just miraculous power tools for making beautiful inside cuts on finished materials. Otherwise a jig saw (sometimes called a saber saw) works, or even a reciprocating saw if you're very careful.

MindBender
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Joined: Fri Aug 19, 2016 4:59 pm

Re: Elbow Boot Ceiling Joist Detail

Post by MindBender » Wed Aug 09, 2017 11:44 am

Appreciate input - nice to have the assurance that I'm heading in the right direction!

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A. Spruce
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Re: Elbow Boot Ceiling Joist Detail

Post by A. Spruce » Wed Aug 09, 2017 1:22 pm

Be sure to box all the way around those boots, keeps them stiff and straight and gives you something to screw the register cover into.
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MindBender
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Joined: Fri Aug 19, 2016 4:59 pm

Re: Elbow Boot Ceiling Joist Detail

Post by MindBender » Wed Aug 09, 2017 1:39 pm

Good point - there is a register in my house where the cover has screws going in at 45 degrees to find wood to hold it up! I plan to use 2x2 long strips between joists and small piece between them to complete a box of 4x10 for the boot.

I have seen sheet metal used to hold up these boxes - is that just to speed up install or is it a new building code requirement.

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Aaron
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Location: St. Paul, MN

Re: Elbow Boot Ceiling Joist Detail

Post by Aaron » Wed Aug 09, 2017 1:52 pm

Sheet metal strips acting as hangers or steel strapping with holes is what I commonly see. I don't think the code is that specific about what to use to support it, but those materials seem to be commonly used in the trade.

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