Outdoor cabinet

[joe milana]

Attempting an unusual project here & looking for input. I am going to attempt to build a TV cabinet to fit into the 55" x 32" opening in the photo.

Attachment 238333
It is a three season room here in the Midwest so, it will be exposed to temperature extremes. I have to preserve the widest side to side dimension, so I will be mounting the cabinet on the exterior side of the opening, and the faceframe & doors to the inside of the opening. See drawing. The green represents the cabinet box, the brown would be the cedar beam, and the red represents the faceframe & doors from a side view.
Attachment 238316

My question is what to construct the cabinet box from. It needs to be board & batten on the exterior to match the existing siding. I would like the interior to be cedar with a clear finish to match the existing woodwork.
I can get 4 x 8 sheets of rough Fir or okoume plywood siding in 5/8" for the exterior side, but that leaves me with the ugly interior side. I haven't seen the ply yet, so I'm not sure it's even "cabinet " grade, so to speak.
If the ply is acceptable, I was thinking I could veneer the inside with some 1/4" cedar.

I was thinking I could hang the cabinet by extending the top & bottom the width of the beam & screwing up into the top beam, and down into the bottom beam. The front edges would be hidden by the face frame. Not sure how to secure the sides yet. Maybe pocket screws if I could hide them.
Attachment 238317

[Jamie Buxton]

The non-show face of siding plywood is ugly. The manufacturers believe that nobody will ever be looking at the non-show face, so they use their lowest-grade wood. You'll want to cover it with something prettier.

How you gonna get electrical power and signal cable into the cabinet?

[joe milana]

I mentioned in my post thinking of veneering the inside of the plywood with 1/4" cedar veneer. I haven't gone to see the plywood yet. I hope it is better than the typical exterior ply that I see at the BORG. You know..looks like a pile of pringles...

I'll run conduit for power & cable up through the bottom of the cabinet from the outside.