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
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?
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
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.
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