Some drywall and framing was demolished around my gas fireplace during a drain tile installation. It looks like the framing/walls around the fireplace are built on 2x4's with fire resistant drywall on both sides — i.e., inside the cavity.

Inside gas fireplace cavity

This isn't quite what I expected to see, just given the tutorials I've seen online. I was expecting 2x4 framing inside, with clearance from the fireplace, and drywall on the outside only.

But, is this the normal, necessary, or safe way to do this? Or, does this look like it was an over-precautious DIY project?

What do I ultimately need to do to restore this safely?


It depends on:

  1. The specs for the unit. Some require an air gap and typically have metal protrusions to enforce that spec. Older ones may have called specifically for fire-resistant wall treatments.
  2. Local building codes. There may be requirements that disregard and enhance manufacturer requirements and recommendations.
  3. The risk tolerance of the builder or homeowner. If it helps you sleep at night to not have kiln-dried lumber directly exposed to a firebox, it's cheap comfort to drop in some drywall. To do it right it would need to be taped or otherwise sealed at the joints, though.
  • and painted, right? I'm just asking because isn't the paper still flammable? I alos wonder what is on the other side of the wall (or what was); could it be a fish tank, an ice chest, etc? Perhaps the intent was to reduce heat radiation. – noybman Jul 21 '19 at 16:32
  • It's still flammable even if painted. If there was something on the other side of the wall, even one layer of gypsum would insulate enough for an aquarium. – isherwood Jul 22 '19 at 12:42
  • 1
    FWIW, I had my local fireplace installer take a look: The box pictured above is actually the fireplace's outer chamber -- or whatever it's called. The cavity is supposed to be air-sealed and insulated on the back wall (exterior wall), and the box is supposed to rest on a platform, which can simply be wooden. But, this answer is clearly "correct" ... in that, there are more types of fireplaces than I realized. And, the only safe answer is clearly, it depends. ... Thanks! – svidgen Jul 25 '19 at 15:45

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