Help - Chimney for range vent
Greetings! I am remodeling our kitchen. In the center of one external wall will be a 48" range, with vent system above, concealing piping up to a 90 which will pass out the wall to an external blower. I have to build an enclosure to contain the vent system, which is a first for me. I am awaiting delivery of the vent equipment next week but am trying to get my thoughts in order and am a little baffled. We prefer the look where is looks like a fireplace mantle, with a slight arch on the front, a shelf some molding and then from there up, it is the same color at the wall. I was planning on buying the arch, molding and shelf and corbels from the cabinet company, but it occurs to me that it might be less excpensive to look for the arch at a millwork supplier?
I'm a little at a loss on this one. I'm guessing that I need to build either a 3 or 4 sided plywood box, open at the top and the bottom, use something like cleats on the inside to support the vent liner and insert and then mount it through the back to the wall studs and possibly also to the ceiling, i.e. the bottom of the floor joists above from the second floor?
I really don't want to use corner molding as I am trying to have it look like a built in fireplace surround, what can I use to cover the overlap seams? I was thinking of corner bead and then maybe actually put a skim coat of light weight taping compound on it? I'm a little leary of trying to miter 45's in those long seams.
The weight of all the ventilation equipment is probably around 100lbs and then there will be vibration. I would normally glue and screw the the box together at the overlaps, Should I be considering something different?
I appreciate any advice you are willing to share.