Ceiling duct boots (flanged vs. unflanged) & ceiling drywall installation

[aunsafe2015]

I'm finishing a walk-up attic and am in the process of running some ceiling ductwork before the ceiling drywall goes up. I'm seeing two kinds of duct boots:

Flanged: https://tinyurl.com/y2oqa8jn

Unflanged: https://tinyurl.com/y4xx69ja

Can anybody tell me why to choose one over the other? It seems that the flanged one gives me something to nail to my framing, but doesn't the rectangular metal that sticks out past the flange interfere with the drywall installation? Seems that it would poke out beyond the flush surface of the framing.

Thanks.

 

[klassenl]

Can anybody tell me why to choose one over the other? It seems that the flanged one gives me something to nail to my framing, but doesn't the rectangular metal that sticks out past the flange interfere with the drywall installation? Seems that it would poke out beyond the flush surface of the framing.

Thanks.

Is this not the point of the flange? If you would nail the flange to the underside of the framing then it would protrude the same amount as the drywall thickness. Then when the drywall is done the bottom of the boot is even with the drywall. The same idea as an electrical box.

 

[JackDiddly]

The protruding part of the boot would be just as klassenl described. If you have never done this before I would recommend the one with the flange unless you frame in your other boot. The problem you will run into is that the register installed after drywall will likely have two screw holes that will be around 3/8" wider than the actual boot and you will play hell trying to mount a register to the edge of the drywall hole without some kind of backing for the screw to bite into.

 

[danski0224]

You want the flanged ones.

There are tricks to "add a flange" to the other style.

 

[aunsafe2015]

Is this not the point of the flange? If you would nail the flange to the underside of the framing then it would protrude the same amount as the drywall thickness. Then when the drywall is done the bottom of the boot is even with the drywall. The same idea as an electrical box.

The protruding part of the boot would be just as klassenl described. If you have never done this before I would recommend the one with the flange unless you frame in your other boot. The problem you will run into is that the register installed after drywall will likely have two screw holes that will be around 3/8" wider than the actual boot and you will play hell trying to mount a register to the edge of the drywall hole without some kind of backing for the screw to bite into.

You want the flanged ones.

There are tricks to "add a flange" to the other style.

Oh, so the drywall guys will have to measure and cut a hole in the drywall before they actually hang the drywall?

 

[yeldogt]

Get the one with the flange .... They are easier to mount and when you go to mount the register the screw will grab the metal.

Yes, the drywall guys will cut the drywall to fit the opening ...

With the flangeless type they are attached from the inside to framing ... you have to make sure there is wood where the register screw is going to be located.


I like the flangeless type with insulation above ... ask the dry wall guys to run some glue/caulk around the flange ... this seals any gaps in the ceiling

 

[danski0224]

Oh, so the drywall guys will have to measure and cut a hole in the drywall before they actually hang the drywall?

Somewhat.

They'll use a Rotozip like tool and cut it out in the air.

 

[Bert_]

Oh, so the drywall guys will have to measure and cut a hole in the drywall before they actually hang the drywall?

They do it just like a can light or fart fan. Screw the corners then cut the hole with a rotozip.

 

[LS6 Tommy]

You need the flanged boots. The unflanged boot is not meant for A/C duct. It's meant to be a transition from an oven hood to round exhaust duct.

Tommy