enigma-2
Member
- Location
- northern Indiana
Code reads "314.20 In Wall or Ceiling. In walls or ceilings with a surface of concrete, tile, gypsum, plaster, or other noncombustible
material, boxes employing a flush-type cover or faceplate shall be installed so that the front edge of the box, plaster ring, extension ring, or listed extender will not be set back of the finished surface more than 6 mm (1/4 in.).
In walls and ceilings constructed of wood or other combustible surface material, boxes, plaster rings, extension rings, or listed extenders shall be flush with the finished surface or project therefrom."
Question come up regarding "Fire Rated Plywood" being used as a wall surface material and the boxes were set back 1/4". Contractor argued the FRP was rated as "noncombustible". NEC does not seem to define exactly what "noncombustible" is. It's my understanding that the rating on FRP is a flame spread type of rating, that is, it retards the spread of fire across the surface of the plywood. (I am assuming that it was listed to ASTM E-84). My understanding of "noncombustible" & "limited-combustible" is a property to resist fire burn through of a material. That is, it's rated as a flammability rating and not a noncombustible rating.
(And we all know that FRP can lose its flammability properties in only a few years under certain conditions.)
We required the contractor to install metal sleeves to bring the sides of the boxes up flush with the wall surface, but would like to get any additional opinions as to how others view this.
material, boxes employing a flush-type cover or faceplate shall be installed so that the front edge of the box, plaster ring, extension ring, or listed extender will not be set back of the finished surface more than 6 mm (1/4 in.).
In walls and ceilings constructed of wood or other combustible surface material, boxes, plaster rings, extension rings, or listed extenders shall be flush with the finished surface or project therefrom."
Question come up regarding "Fire Rated Plywood" being used as a wall surface material and the boxes were set back 1/4". Contractor argued the FRP was rated as "noncombustible". NEC does not seem to define exactly what "noncombustible" is. It's my understanding that the rating on FRP is a flame spread type of rating, that is, it retards the spread of fire across the surface of the plywood. (I am assuming that it was listed to ASTM E-84). My understanding of "noncombustible" & "limited-combustible" is a property to resist fire burn through of a material. That is, it's rated as a flammability rating and not a noncombustible rating.
(And we all know that FRP can lose its flammability properties in only a few years under certain conditions.)
We required the contractor to install metal sleeves to bring the sides of the boxes up flush with the wall surface, but would like to get any additional opinions as to how others view this.
