Metal boxes in wall

Old 04-01-14, 12:44 AM
nugmebot's Avatar
Thread Starter
Join Date: Feb 2012
Location: U.S.
Posts: 58
Upvotes: 0
Received 0 Upvotes on 0 Posts
Metal boxes in wall

I'm looking at a condo built in 1990 and was trying to figure out a little more how it was built. This is a "ground floor" unit which is basically a daylight basement as it is built in to the hillside. Only one side has windows; this side is all at/above grade. The unit sits on top of an all-concrete parking garage which is mostly underground. A couple parts have linoleum which feels really solid so I'm assuming this unit is built on a concrete slab (the roof of the garage).

I popped off one of the outlet plate covers on a common wall to see what was inside the wall. It was hard to tell, but it looks like the outlet was mounted in a 2 gang metal box with a 1 gang adapter, such as the following:


It was definitely a metal box inside. Much roomier than the standard 1 gang boxes. The drywall cutout was about the same as what you'd have for a plastic ox. Normally I'm used to seeing plastic 1 gang boxes nailed to a stud. I've never seen this before and am just curious as to what is going on here and what advantages there are to using metal boxes.
Attached Images   
Old 04-01-14, 04:26 AM
Join Date: Feb 2006
Location: USA
Posts: 6,401
Received 63 Upvotes on 55 Posts
Metal Boxes

Metal boxes are used with metal conduit.
Old 04-01-14, 04:52 AM
CasualJoe's Avatar
Join Date: Jan 2010
Location: United States
Posts: 9,872
Received 185 Upvotes on 166 Posts
I've never seen this before and am just curious as to what is going on here and what advantages there are to using metal boxes.
The 4 inch, 1900, boxes have a lot more room in them and yes, they are generally used in conduit systems. It appears your unit was built more like a commercial job than a residential job, not a bad thing.
Old 04-01-14, 07:35 AM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 13,979
Received 195 Upvotes on 171 Posts
A normal construction technique is to have a masonry wall between two units. The inside walls are furred out with metal studs or 2x furring strips. This allows the interior finish to be installed without loosing too much floor space. Standard plastic boxes are too deep for these walls so the metal boxes are used with plaster rings. Same amount of space just not as deep.
Old 04-01-14, 10:17 AM
Forum Topic Moderator
Join Date: Sep 2005
Location: USA
Posts: 6,099
Received 422 Upvotes on 375 Posts
Metal boxes are used with metal conduit.
Could be conduit or MC/AC type cable. All need to be terminated to metal boxes.
Old 04-01-14, 04:56 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 14,340
Received 878 Upvotes on 741 Posts
We find it easier to wire with metallic wiring methods (boxes, conduit, MC/AC cables) when metal framing is used. Metal framing and drywall is almost fire proof.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: