Combustible Surfaces and Boxes

[busman]

I feel like I'm being clueless here. Obviously, we all know that flush mount boxes need to have the surface within 1/8" of the box edge. However, I went and looked at this code section for another reason, and noticed that it says "Noncombustible Surfaces". Is there another Code rule that I'm missing, or does this mean that if the surface is Combustible (let's say wood paneling) the gap around the box can be any size?

Thanks,

Mark

 

[petersonra]

I feel like I'm being clueless here. Obviously, we all know that flush mount boxes need to have the surface within 1/8" of the box edge. However, I went and looked at this code section for another reason, and noticed that it says "Noncombustible Surfaces". Is there another Code rule that I'm missing, or does this mean that if the surface is Combustible (let's say wood paneling) the gap around the box can be any size?

Thanks,

Mark

View attachment 2573857

It does not actually say that.

The provision you copied out of the code only applies to noncombustible surfaces. There might be something else that applies to combustible surfaces.

I have occasionally wondered about this kind of requirement. Wall paper is combustible, so if there is wall paper over the noncombustible surface does that make it a combustible surface?

 

[busman]

It does not actually say that.

The provision you copied out of the code only applies to noncombustible surfaces. There might be something else that applies to combustible surfaces.

I have occasionally wondered about this kind of requirement. Wall paper is combustible, so if there is wall paper over the noncombustible surface does that make it a combustible surface?

Thanks. What I'm saying is that I can't find one for combustible surfaces. Maybe I didn't say it well.

Mark

 

[hbiss]

What I'm saying is that I can't find one for combustible surfaces.

Although they don't come out and say it, by default, the box edge must be flush with the surface.

-Hal

 

[busman]

Although they don't come out and say it, by default, the box edge must be flush with the surface.

-Hal

Thanks. I think they do say that explicitly for combustible surfaces in 314.20, but to me "flush" means front-to-back (comes out flush with the finished surface). I'm not sure that precludes a gap "side-to-side" or laterally.

Mark