Setting boxes flush with the wall surface
In drywall, plaster, tile and other noncombustible finishes, a box may sit no more than ¼ in. behind the finished surface. In wood or other combustible finishes, it must be flush with the surface or stick out from it.
What the code requires
In concrete, tile, gypsum board, plaster or other noncombustible surfaces, the front of the box, or of any plaster ring, extension ring or listed extender on it, may sit no more than ¼ in. (6 mm) behind the finished surface. This applies to boxes with flush-type covers too.
In wood or other combustible surfaces, the box, ring or extender must be flush with the finished surface or project out from it. No setback is allowed.
A companion rule, 314.21, covers the gap around the box. In drywall, plaster and other noncombustible surfaces, gaps at the edge of the box must be repaired so that none is wider than ⅛ in.
On the job
- Boxes often end up recessed more than ¼ in. after tile, stone or a backsplash is added over the original wall. The usual correction is a listed box extender or extension ring.
- Any setback behind wood paneling or wood trim is a violation, because the box edge must reach the surface.
- Ragged drywall cut-outs with gaps wider than ⅛ in. need patching before the devices and cover plates go on.
Related sections
- NEC 314.21
- NEC 314.16: Box fill: how many wires fit in a box
- NEC 314.29: Junction boxes must stay accessible
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CSLB #354550 · C-10 Electrical · Licensed since 1978 · $25,000 contractor's bond