Backer boxes for the pot lights are finally done. A bit of a tedious process building 15 of them, but it'll be worth it. I used 2 sheets of 7/16 OSB to make the boxes and lined the inside with 5/8 drywall. GG in between the OSB and drywall, and acoustical sealant to seal it all up. Each box weighs just over 8 lbs. I'm using drywall instead of better, fireproof cement backer board, simply because it's easier to cut and since I'm using IC rated pot light enclosures with LED bulbs, I'm not at all concerned about the heat. Even if I used halogens, I should be fine since they'll be in IC enclosures.
I planned out all my rips of the OSB and had the guy at Home Depot use their fancy saw to cut it all up into strips for me. ie, the sides of my boxes are 6.5" tall, and the bottom panels are 8" wide, so they ripped 6.5", 8", etc. strips.
I brought home the strips then cut the other dimension with my mitre saw, to produce all the parts needed for assembly. I also hand cut all the drywall lining panels before hand as well to get these babies built as quickly and efficiently as possible. Here's my piles of panels, except for one drywall panel as I had ran out of scrap 5/8, and had to go buy another sheet to finish this project, but didn't snap another photo.
With all the panels ready to go, I started assembling the boxes. I glued all the joints with LePage PL400 wood construction adhesive, and stapled them all together. After doing this 15 times, I then ran acoustic sealant across the inside of every joint:
Then for each box, I green glued the drywall panels:
and popped them in:
Again, I ran acoustic sealant across the joints and then ran a bead of acoustic sealant across the top edge of the drywall panels, and a bead of PL400 across the edge of the OSB box:
then stapled on the flanges that will rest on the backside of the ceiling drywall. I'll have a ton of acoustic sealant on these flanges when the ceiling panels go up so the boxes are nice and sealed to the ceiling.
Here's what they look like with the Halo IC light can in them.
There's not a ton of room around the boxes which would make wiring them a challenge if I was doing this in the right order. If I had to wire them with the boxes up in place, I would have made these boxes longer. Since I'm retrofitting 14 of these over already wired boxes, this is no issue. I'll be cutting a slot on the short side of the box to slip the romex through, then acoustic sealing the slot, and covering it with a layer of 5/8 drywall for good measure.
The almost finished pile:
All that's left is to glue and staple on straps 1 1/8 back from the faces so that these babies can rest on the hat channel temporarily. The generous helping of acoustic sealant that I'll apply to the flange and cans themselves should then lift these slightly off the hat channel so that they ultimately rest on the backside of the ceiling drywall itself.Edited by Swervepf - 9/16/13 at 9:48am