Metal Boxes / EMT on Basement Wall - when is it OK?

My understanding is that you cannot attach boxes directly to masonry, period. But I'm sure someone will come along and provide more and better detail.

Bill-

Sounds to me like you answered your own question.

The NEC is concerned about corrosion of the metallic box; hence the requirement for the 1/4" airspace. so as not to trap any moisture behind the box,

I'm sure you've seen the surface mounted box in somebody's damp nasty basement that is all rusted out.

Install with the airpace & the box will be fine. Don't use wood or any material that will retain mositure; metal washers would work.

cheers Bob

Thanks bob -- however, someone on here said that the 1/4" airspace requirement didn't apply to device boxes? Is this true of false?

I found a Web site some time ago that recommended against using wood between a panel and a concrete wall and said that some jurisdictions even prohibit it. I don't recall whether it said this was because the wood could become a fire hazard or because it could get waterlogged.

The new panel I bought but haven't yet installed has raised sections on the back where the bolts/screws/fasteners go, so that very little of the box would be in contact with the wall to which it is mounted. Does this mean that I could fasten it directly to the concrete basement wall -- and run pieces of wood alongside (but spaced away from the sides of the panel) to which the Romex can be stapled?

Perce

On 05/01/05 01:18 pm BobK207 tossed the following ingredients into the ever-growing pot of cybersoup:

I don't know for sure about whether the 1/4" space applies to device boxes. Just based on experience, if there is moisture / dampness that can be trapped behind the box you'll enetually have a corrosion problem.

If moisture / dampness is a potential problem, stay away from materials that can absorp it & help corrode the metal.

Metal & wood will last a very long if kept dry. If not, they can be destroyed VERY quickly.

cheers Bob