Boxes in a Wood Ceiling

J

Jimmy7

Senior Member
Location
Boston, MA
Occupation
Electrician
I took down these surface mounted ceiling fixtures and saw that they were being held up by octagon boxes in a wooden ceiling. The problem is that there is about a 1/2 gap around the box to the wood, and the box is about a 1/2 above the edge of the finished ceiling. The new fixtures are about 8” diameter ceiling fixtures, so they will cover the hole. Don’t I need something to fill in the area around the box to the edges of the wood ceiling? I could use an Arlington plastic box extender to bring it down to the edge of the ceiling, but what around the box?
 
Would this apply to your installation?

314.25(B) Exposed Combustible Wall or Ceiling Finish.
Where a luminaire canopy or pan is used, any combustible wall or ceiling finish exposed between the edge of the canopy or pan and the outlet box shall be covered with noncombustible material if required by 410.23.

410.23 Covering of Combustible Material at Outlet Boxes.
Any combustible wall or ceiling finish exposed between the edge of a luminaire canopy or pan and an outlet box having a surface area of 1160 mm2 (180 in.2) or more shall be covered with noncombustible
material.
Click to expand...
 
Jimmy7 said:
I took down these surface mounted ceiling fixtures and saw that they were being held up by octagon boxes in a wooden ceiling. The problem is that there is about a 1/2 gap around the box to the wood, and the box is about a 1/2 above the edge of the finished ceiling. The new fixtures are about 8” diameter ceiling fixtures, so they will cover the hole. Don’t I need something to fill in the area around the box to the edges of the wood ceiling? I could use an Arlington plastic box extender to bring it down to the edge of the ceiling, but what around the box?
Click to expand...
Yes but you can buy box extenders

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Yes, I was going to use one of those extenders that will bring me down to finish ceiling. Would this extender satisfy around the perimeter of the box where it sits approximately a 1/2 from the wood on all sides?
Picture a bar box sitting in the middle of a 5” to 6” hole
 
I think for the building code around here I would need spray foam too. I can install the box extender and then use a fire rated spray foam. Can anyone recommend a spray foam? Is there specific ones to be used around cables?
 
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