The interior of my home will have 1″ of foamboard on all exterior walls. How can I mount the electrical boxes? They would need to protrude 1″ for the foam plus 1/2″ for the sheetrock. I don’t know of any boxes that have either a rear mounted nailing flange or can be back mounted through the box. Any suggestions other then useing a block to move the box out (I would then have to cut the foam around these blocks as well as the box. Stumped!
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
The team offers expert advice on building an affordable new home that follows building-science best practices.
Featured Video
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
First of all, I would mount the foam board on the exterior side of the wall. And for those exterior boxes, they sell a box that will telescope by turning a couple of screws.
You get out of life what you put into it......minus taxes.
Marv
Well the answer is "mud rings." These are extensions of the box in middling regular increments. 1.5" might not be in stock at your local big box store, so you might have to find an electrical supply house nearby (or make on order over the internet).
Foam on inside or out is too hugel complicated to argue here. Especially with so many certain they know the one true answer no matter what. Doubly so since your Profile includes no location informantion--you could be building from 0º to 60º lattitude, and it anc matter.
Akthough, having waded through Lstiburek's missive on drying water vapor out of houses, I've too many options swimming through my head, with the impermiable plane from all the way inside to all the way outside <aieieieie>
HD and Lowes have 1.5" deep "single" and "double" box rings.
HD and Lowes
Yours may; mine only has 5/8" and 1" on the shelf. They have all sorts of things online, though.Occupational hazard of my occupation not being around (sorry Bubba)
There are two easy ways to beat that problem.
1) Use adjustable plastic boxes. They allow for about 2" of adjustment beyond the face of the stud.
2) Use regular deep plastic boxes and drill a hole in the very back of the box from side to side. Drill a hole near the top of the box and one near the bottom. Make the hole just big enough to accomodate a 16cc sinker. Slide the nails through the holes and nail the box to the stud so that 1 1/2" of the box is protruding past the stud. This is the cheap way to do it if you have time to spare for drilling the boxes.
Edited 4/27/2009 8:33 pm ET by BoJangles
Just thinking out loud here, but wouldn't the exposed nails in the box need to be bonded?
Jon Blakemore RappahannockINC.com Fredericksburg, VA
bonded...
Technically yes, have seen similar technique pass inspection here by covering the nail / screw heads with tape (like that will stay forever) or silicone caulk.
Also have seen deep metal boxes rebored for similar installation - metal box provides bond for fasteners. This technique always passes inspection.
JimNever underestimate the value of a sharp pencil or good light.
Just thinking out loud here, but wouldn't the exposed nails in the box need to be bonded?
No, at least not according to the inspectors we deal with. Even if one of the nails got energized, there's no threat to anyone. It's not contacting anything metallic and it's not accessible.
You can do the same thing with a metal box if you prefer. In that case, the box will be grounded.
use foil faced foam, tape the joints to create a vapor barrier (dont forget to disabel your existing V.B. if you have one. or use un faced EPS no tape and V.B. over that.) fur out over the foam with 2X2 run your elec through there using 1 1/2" boxes and BINGO a continuous V.B., sheetrock backer, and elec. chases.
"A small leak can sink a great ship."
-Benjamin Franklin-
it's whammo-zammo!!!
definitely use furring strips atop your foam, but you forgot to mention to ensure that your wall panel fasteners(be they screws or nails)aren't so long that they puncture the vb on the other side of said furring strips.......and I'll buy that for a dollar..All I ever wanted in life was an unfair advantage...