So my contractor installed USG Sheetrock Brand drywall which we plan to install vinyl siding over on an ADU. The inspector said it should be mold & moisture resistant so we should have used Gold Bond drywall.

Question is, can we install something else over the drywall to make it pass the inspection or will the whole drywall need to be re-done with Gold Bond?

  • 1
    In this case, the only answer is "Ask the inspector." He or She is the authoritative source. Oct 19, 2021 at 19:51
  • He left the door open to "find a listed product" that can be installed over the drywall. Thats why I came here...hoping for a miracle : )
    – Marvel Moe
    Oct 19, 2021 at 19:54
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    Guess I don't understand why anyone would use a drywall type product in an exterior application, whether it's going to be covered with something else of not.
    – SteveSh
    Oct 19, 2021 at 23:18
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    @SteveSh Drywall products are used on the exterior side of buildings for fire protection requirements. If the ADU is within the “fire code setback area” then drywall can give the wall the fire protection to comply with Planning Departure requirements. (Still needs to be moisture resistant. I’d substitute a moisture barrier on the non-moisture resistant wallboard and then apply the exterior siding, etc.)
    – Lee Sam
    Oct 20, 2021 at 0:25
  • The branding doesn't matter here. What matters is the actual type of product used -- was this standard interior drywall, a "moisture-resistant" drywall product (like "greenboard"), or a glass-mat gypsum sheathing that uses fiberglass instead of paper for the face layers? Oct 20, 2021 at 2:00

1 Answer 1


Actual wall sheathing, perhaps?

One of the "sheathing duty" foam sheet insulation products; or a normal sheathing product such as OSB, cementboard, or plywood.

Drywall as exterior siding is a bizarre choice since it has little strength and is not very moisture resistant compared to "normal" sheathing even if it is the moisture resistant type.

  • That was the basis of my comment above.
    – SteveSh
    Oct 20, 2021 at 12:32

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