I want to build a wooden box of size about 16 inch height x 24 wide x 20
long. It is a return air plenum. The "box" will not have a bottom (where the
return air duct is) and no front (where the grill cover is). Right now the
entire wall cavity is the plenum but I need to clean it up. If you want to
know the details you can read my previous post.

Should I use 2x2 or L brackets to screw the wood panels together? L-brackets
seems easier because I won't have to drive long screws through a 2x2 inside
a small wall cavity. But I also feel using L brackets is not as good as a
2x2.

Also, what thickness wood panels should I use? 1/4 inch plywood seems strong
enough. However they tend to warp a little over time. If the box is held
together with L brackets (say two brackets per edge), warping could create
unwanted gaps. 1/2 inch plywood would stay straight, but seems overkill. I
see some material call hardboard that is 1/4 inch think with a vinyl
coating. Could those be used?

On Sun, 27 Oct 2013 18:13:46 -0700, "bob" wrote:

I want to build a wooden box of size about 16 inch height x 24 wide x 20
long. It is a return air plenum. The "box" will not have a bottom (where the
return air duct is) and no front (where the grill cover is). Right now the
entire wall cavity is the plenum but I need to clean it up. If you want to
know the details you can read my previous post.

Should I use 2x2 or L brackets to screw the wood panels together? L-brackets
seems easier because I won't have to drive long screws through a 2x2 inside
a small wall cavity. But I also feel using L brackets is not as good as a
2x2.

Also, what thickness wood panels should I use? 1/4 inch plywood seems strong
enough. However they tend to warp a little over time. If the box is held
together with L brackets (say two brackets per edge), warping could create
unwanted gaps. 1/2 inch plywood would stay straight, but seems overkill. I
see some material call hardboard that is 1/4 inch think with a vinyl
coating. Could those be used?
I'd use 3/8" ply and 1X2 spruce, or 1/4" ply - screw the 1X2 to the
studs, then liquid nails to hold and seal the ply to the 1X2 cleats.

On 10/27/2013 08:13 PM, bob wrote:
I want to build a wooden box of size about 16 inch height x 24 wide x 20
long. It is a return air plenum. The "box" will not have a bottom (where
the return air duct is) and no front (where the grill cover is). Right
now the entire wall cavity is the plenum but I need to clean it up. If
you want to know the details you can read my previous post.

Should I use 2x2 or L brackets to screw the wood panels together?
L-brackets seems easier because I won't have to drive long screws
through a 2x2 inside a small wall cavity. But I also feel using L
brackets is not as good as a 2x2.

Also, what thickness wood panels should I use? 1/4 inch plywood seems
strong enough. However they tend to warp a little over time. If the box
is held together with L brackets (say two brackets per edge), warping
could create unwanted gaps. 1/2 inch plywood would stay straight, but
seems overkill. I see some material call hardboard that is 1/4 inch
think with a vinyl coating. Could those be used?



A wooden plenum would possibly not meet the building code.
IIRC you were given proper advice the first time you posted so you
should take it. When in doubt, err on the side of caution.

--
http://www.youtube.com/watch?v=MS85K...ature=youtu.be

On 10/27/2013 9:13 PM, bob wrote:
I want to build a wooden box of size about 16 inch height x 24 wide x 20
long. It is a return air plenum. The "box" will not have a bottom (where
the return air duct is) and no front (where the grill cover is). Right
now the entire wall cavity is the plenum but I need to clean it up. If
you want to know the details you can read my previous post.

Should I use 2x2 or L brackets to screw the wood panels together?
L-brackets seems easier because I won't have to drive long screws
through a 2x2 inside a small wall cavity. But I also feel using L
brackets is not as good as a 2x2.

Also, what thickness wood panels should I use? 1/4 inch plywood seems
strong enough. However they tend to warp a little over time. If the box
is held together with L brackets (say two brackets per edge), warping
could create unwanted gaps. 1/2 inch plywood would stay straight, but
seems overkill. I see some material call hardboard that is 1/4 inch
think with a vinyl coating. Could those be used?

Most plenum I've seen, have been sheet metal. What's the appeal of wood?
Sounds like you're doing it for cosmetic reasons? If that's the case,
use what the nearby building uses, so it looks similar.


--
..
Christopher A. Young
Learn about Jesus
www.lds.org
..

Stormin Mormon wrote:
On 10/27/2013 9:13 PM, bob wrote:
I want to build a wooden box of size about 16 inch height x 24 wide
x 20 long. It is a return air plenum. The "box" will not have a
bottom (where the return air duct is) and no front (where the grill
cover is). Right now the entire wall cavity is the plenum but I need
to clean it up. If you want to know the details you can read my
previous post. Should I use 2x2 or L brackets to screw the wood panels
together?
L-brackets seems easier because I won't have to drive long screws
through a 2x2 inside a small wall cavity. But I also feel using L
brackets is not as good as a 2x2.

Also, what thickness wood panels should I use? 1/4 inch plywood seems
strong enough. However they tend to warp a little over time. If the
box is held together with L brackets (say two brackets per edge),
warping could create unwanted gaps. 1/2 inch plywood would stay
straight, but seems overkill. I see some material call hardboard
that is 1/4 inch think with a vinyl coating. Could those be used?

Most plenum I've seen, have been sheet metal. What's the appeal of
wood? Sounds like you're doing it for cosmetic reasons? If that's the
case, use what the nearby building uses, so it looks similar.

Apparently, it is just a box for a return duct, not a supply duct. He
posted about this on 10/16/2013 with the subject heading, "isolating furnace
intake".

My vote would be 1x2's, 1/4-inch or 3/8-inch plywood, nail or screw it
together, use some construction adhesive to help seal it (maybe Loctite
Power Grab, which works great). Then use screws to attach it in place.
Have fun. It will be hidden behind the wall and doesn't need to be fancy.