Help: Adding light box in space with vent stack

[benji]

I am helping someone do a minor bathroom remodel and have run into a bit of a snag. It's not strictly a plumbing problem, but does involve the vent stack.

We want to install a new light fixture over the sink where there was no fixture before, so we need to install a light fixture box. The box needs to be right in between two studs (16" OC). Unfortunately, the vent pipe (black ABS) runs through the same space, making it difficult/impossible to use an old-work box with "ears". Here is a quick diagram of the situation:



The vent pipe is about 2" OD, so there's a bit of space behind the pipe (a bit over an inch). The wall is double-thickness drywall; 5/8" of normal wallboard under 5/8" of blueboard. We cannot go in from the back side, as this is a condo and the other side of the wall is another unit.

Any ideas about how to mount the light box at the proper depth, etc. without re-routing the vent pipe? Thanks!

[LazyPup]

You could get an electical junction box in by using a PVC plastic rework box with swing out plaster ears.

The ears are flat against the sides of the electrical box until the box is slid into the opening, then as the phillips head screw it tightered down the mounts swing out behind the wallboard and draw forward locking the junction box against the sheetrock, however I see two other concerns with this idea.

I am not sure that this type of electrical box would be permitted to be a loadbearing box. I beleive the light fixture would have to be self supported on the outside of the wall rather than rely upon the electrical box for support. (Maybe Hayzee will fill us in on that point)

My greater concern is the double layer of sheetrock. You stated that this wall has two layers of 5/8 sheetrock and this wall is a dividing wall between separate living spaces in a condo.

In most states a Condo or aparment building with up to 3 living units is considered a residential structure and falls under the residential codes, however, if the structure has 4 or more living units it is classified as a commercial living structure and falls under the commercial codes.

In either case, A wall such as you describe with double layers of 5/8 sheetrock on both sides of the studding is more than likely a "Fire Rated Wall" which is required between living units in apartments and condo's, or in single family residential structures with an attached garage it is required between the garage and the living space.

All electical passing through a "Fire Rated Wall" are required to run through a conduit for the minimum of the wall thickness, all HVAC ducting requires a fire damper, and ALL OPENINGS around plumbing pipes, electrical conduits or hvac ducting are required to be sealed with an approved firerated caulking material.

[benji]

quote:Originally posted by LazyPup
[I am not sure that this type of electrical box would be permitted to be a loadbearing box. I beleive the light fixture would have to be self supported on the outside of the wall rather than rely upon the electrical box for support.

That does give me an idea, though. If I put a piece of 1x4 across the opening, screwed into the studs on either end, I could just mount a box into that. It might project 3/4", but an little decorative edging and it might look nice.

quote:In either case, A wall such as you describe with double layers of 5/8 sheetrock on both sides of the studding is more than likely a "Fire Rated Wall" which is required between living units in apartments and condo's, or in single family residential structures with an attached garage it is required between the garage and the living space.

All electical passing through a "Fire Rated Wall" are required to run through a conduit for the minimum of the wall thickness, all HVAC ducting requires a fire damper, and ALL OPENINGS around plumbing pipes, electrical conduits or hvac ducting are required to be sealed with an approved firerated caulking material.

Thanks for the heads up. I do know, however, that the original wiring is not in conduit... in fact, it's not even run into a junction box! The original fixture was a flourescent one mounted to the wall; the Romex just came out of a hole in the wall where you couldn't see it, and into the strain-relief entry on the fixture itself. That's why I have to mount a new light box... there is none at all there now.

FWIW, the condos were built probably early '80s and we are in Colorado.

[HayZee518]

Benji - take a look at the two posts in electrical aimed at your problem - Hayzee