Commercial remodel - old work box okay?

[catronics]

I'm new to commercial buildings with steel studs, and I'm starting a job retrofitting/installing LED track lighting and backlighting for some large interior display signs. They need new switches where there are none now. Pretty ordinary work in my residential and small businesses jobs - I'll often use a plastic or steel old work box.

Can I use a steel remodel box in this type of building with steel studs? Does Code allow it? And what kind of box/bracket do you recommend?

 

[dkidd]

I'm new to commercial buildings with steel studs, and I'm starting a job retrofitting/installing LED track lighting and backlighting for some large interior display signs. They need new switches where there are none now. Pretty ordinary work in my residential and small businesses jobs - I'll often use a plastic or steel old work box.

Can I use a steel remodel box in this type of building with steel studs? Does Code allow it? And what kind of box/bracket do you recommend?

Watch out for fire rated walls. Otherwise, unless there is a specification, there should be no issues even with plastic.

 

[catronics]

How would I know if it's a fire rated wall?

And plastic? I thought that was a no-no.

 

[MAC702]

And plastic? I thought that was a no-no.

Local building codes might care. The NEC doesn't.

 

[Coppersmith]

Usually in that type of building I am running MC or EMT so metal boxes are needed. If I were running ENT or NM, then plastic boxes would be fine (assuming no local code forbids it). Steel studs don't impose additional requirements except bushings if running NM through them. There are boxes and support pieces designed for steel studs that can make your work faster. Take a look at Enrico/Caddy products. If you see a wall that has two or more layers of drywall or is thicker than 1/2" or is marked (above the drop ceiling usually) "one hour rated" or "two hour rated" or "protect all openings" then it is definitely a fire wall. Other walls may be fire walls. You can't tell without the blueprints.

 

[electrofelon]

For old work with mc, I usually use 2x3 metal boxes with battleships/Madison bars. I like the integral mc box clamps rather than connectors as the connectors make getting the box in more difficult.

 

[growler]

If you see a wall that has two or more layers of drywall or is thicker than 1/2" or is marked "one hour rated" or "two hour rated" or "protect all openings" then it is definitely a fire wall. Other walls may be fire walls. You can't tell without the blueprints.

Also if it's a wall that separates tenant spaces and goes all the way to the roof it's fire rated. A lot of the time you can tell by looking at other conduits and pipes going through walls, if they bother to seal the openings that a good sign it's fire rated.

 

[electrofelon]

Watch out for fire rated walls. Otherwise, unless there is a specification, there should be no issues even with plastic.

There always seems to be some confusion with this, but aren't pretty much all boxes 2 hr rated?

 

[dkidd]

Also if it's a wall that separates tenant spaces and goes all the way to the roof it's fire rated. A lot of the time you can tell by looking at other conduits and pipes going through walls, if they bother to seal the openings that a good sign it's fire rated.

Not necessarily. Sometimes it is done for sound attenuation.

 

[tkb]

There always seems to be some confusion with this, but aren't pretty much all boxes 2 hr rated?

Its not the box, it the mounting.
In a fire rated wall you cannot cut in the box and use Madison clips.
The box needs to be mounted to a framing member.

 

[mtfallsmikey]

And... a plastic box is not plenum rated for use in a ceiling...??

 

[oldsparky52]

Its not the box, it the mounting.
In a fire rated wall you cannot cut in the box and use Madison clips.
The box needs to be mounted to a framing member.

I did not know that. Is that a building requirement? Any idea as to why the box has to be mounted to the framing member in a fire rated wall?

 

[david]

Local building codes might care. The NEC doesn't.

How do you know a plastic device box is ok with out knowing the wiring method being used?

 

[cowboyjwc]

Watch out for fire rated walls. Otherwise, unless there is a specification, there should be no issues even with plastic.

Very important and a very common mistake and it gets worse if it's a two hour wall.

 

[cowboyjwc]

I did not know that. Is that a building requirement? Any idea as to why the box has to be mounted to the framing member in a fire rated wall?

It's part of the hose test. if the fire is really going and you hit a nonsecured box with the fire hose and blow it out, you've created an opening that the fire could pass through. The purpose of the rated wall is to keep the fire contained as long as possible.

 

[GerryB]

It's part of the hose test. if the fire is really going and you hit a nonsecured box with the fire hose and blow it out, you've created an opening that the fire could pass through. The purpose of the rated wall is to keep the fire contained as long as possible.

When I read it I remember hearing it had to be attached to a framing member but had no idea why. So that would be in the IBC?

 

[oldsparky52]

It's part of the hose test. if the fire is really going and you hit a nonsecured box with the fire hose and blow it out, you've created an opening that the fire could pass through. The purpose of the rated wall is to keep the fire contained as long as possible.

Thank you!

 

[roger]

I did not know that. Is that a building requirement? Any idea as to why the box has to be mounted to the framing member in a fire rated wall?

It's a UL requirement.


From the UL Fire Resistance Directory (The Orange Books)


WALL AND PARTITION ASSEMBLIES

Metallic Eletrical Outlet Boxes

Listed single and double gang metallic outlet and switch boxes with metallic or nonmetalliccover plates may be used in bearing and nonbearing wood stud and steel stud walls with ratings not exceeding 2h. These walls shall have gypsum wallboard facings similar to those shown in Design Nos. U301,U411, and U425. The metallic outlet or switch boxes shall be securely fastened to the studs and the opening in the wallboard facing shall be cut so that the clearance between the box and the wallboard does not exceed 1/8 in. The surface area of individual metallic outlet or switch boxes shall not exceed 16 sq in. The aggregate surface area of the boxes shall not exceed 100 sq in per 100 sq ft of wall surface.



Roger

 

[Coppersmith]

Most metal boxes secured to metal studs that I have seen will easily push away from the drywall surface (swing like on a hinge) when there is no cover plate attached. Does that fit the definition of securely attached?

 

[oldsparky52]

It's a UL requirement.


From the UL Fire Resistance Directory (The Orange Books)


WALL AND PARTITION ASSEMBLIES

Metallic Eletrical Outlet Boxes

Listed single and double gang metallic outlet and switch boxes with metallic or nonmetalliccover plates may be used in bearing and nonbearing wood stud and steel stud walls with ratings not exceeding 2h. These walls shall have gypsum wallboard facings similar to those shown in Design Nos. U301,U411, and U425. The metallic outlet or switch boxes shall be securely fastened to the studs and the opening in the wallboard facing shall be cut so that the clearance between the box and the wallboard does not exceed 1/8 in. The surface area of individual metallic outlet or switch boxes shall not exceed 16 sq in. The aggregate surface area of the boxes shall not exceed 100 sq in per 100 sq ft of wall surface.



Roger

Thank you! I guess that means no more than a 2-gang box too?