My fire sprinkler contractor says that we need to install 5/8" 60-min fire rated drywall in all ceilings, but my GC says 1/2" will pass code. Who is right?

If the code does call for 60-minute drywall, which inspector would be checking for it? The fire department inspects the sprinkler system prior to drywall, so I'm thinking that would leave the inspector who comes in right after drywall hanging. Am I right?

  • What Codes apply in your jurisdiction? Commented Apr 8, 2018 at 2:14
  • My city is subject to 2016 CA Residential Code, which is based on 2015IRC, with some CA-specific amendments and using NEC for electrical, mechanical, and plumbing: Commented Apr 8, 2018 at 18:54
  • @CoinToss1010 When in doubt, call your local building inspector - it's rare for them not to be helpful and informative.
    – tahwos
    Commented Apr 9, 2018 at 1:07

1 Answer 1


I doubt you need a 1-hour Fire rated ceiling.

Fire sprinklers eliminate the need for fire rated construction in wood frame buildings, unless 1) encroachment on property line setback requirements, 2) hazardous storage facility, 3) fire separation between an occupancy type “I” (institutional) and other occupancies.

Also, it may be required under local sub-division requirements (CC&R’s).

However, fire ratings are based on SYSTEMS. if you need a 1-hour fire rated SYSTEM, you can use: 1) 5/8” Type “X” on the ceilings with joists spaced up to 24” oc, or 2) 1/2” Type “C” gypsum board on the ceiling with joist spacing up to 16” oc. If you need to space the framing further apart than 24”, you can add stripping, but nailing is critical...I’d check with the local Building Official.

Remember, nailing size, type and spacing is critical.

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