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Does the Baco code require double 5/8" 0n the garage ceiling when there is a living space above ?

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    Unless you're installing sheetrock in a nuclear reactor, what is Baco Code? What's your location?
    – JPhi1618
    Mar 19 '20 at 17:37
  • 5/8 what, and what jPhi1618 said, what is Baco ?
    – Alaska Man
    Mar 19 '20 at 17:55
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    I thought it was required on the walls but thicker on the ceiling , but it is required to isolate a living space from a garage.
    – Ed Beal
    Mar 19 '20 at 18:50
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    Hello, and welcome to Home Improvement. Unfortunately, we'll need more info before we have any chance of helping you. Please take our tour so you'll know how best to participate here. Mar 19 '20 at 19:14
  • Check with local code enforcement cuz guess what, in a city near me you would have to install automatic fire sprinklers in the garage. Mar 20 '20 at 5:15
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In residential construction up through duplexes, 1-hour Fire rating (1 layer) is required on the garage side of the ceiling and walls when there is a living space on the other side.

When you have 3 units or more, then you MAY need 2 layers, depending on the size of the complex and type of construction.

For ceilings in 1 and 2 unit residential units: 1 layer installed on 2x lumber and/or I-joists correctly gives you “1-hour” construction. In order to obtain the “1-hour” designation 5/8” type-X gypsum board must be installed on joists at 24” on center (max.) fastened with Type W or S drywall screws at 12” on center along all supports, and then “rough” taped. (See ICC Table 721.1(3), item 21.)

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I'm sure that you mean BOCA (Building Officials Code Administrators) rather than Baco. But I'm also sure that you probably need to adhere to the IBC (International Building Code)

You need (1) layer of 5/8" drywall and it needs to be mudded and taped to get the needed fire rating

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I have never seen local code in my life requiring a double sheet of dry or more than 5/8". Period.

To second this due to the weight of the 5/8" drywall there would be some innate issues installing it over the top of another 5/8" sheet. It could be done but your screws not having framing for the first 5/8" is a recipe for failure. So either this is the weirdest city in America or you are reading code wrong.

Note: It is very normal to require 5/8" drywall on all adjoining walls. Which means your ceiling would need to abide.

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    There are floor ceilings in the UL fire resistance database that use multiple layers of Type X or C...I'd look at those if you want an idea of how such a thing is done Mar 19 '20 at 22:35
  • @ThreePhaseEel - Are we talking residential? This is a Home Improvement site.
    – DMoore
    Mar 20 '20 at 6:01
  • Nothing says you can't use such an assembly in residential work (although it's far more common to see that level of detailing in multifamily) Mar 20 '20 at 11:38
  • @ThreePhaseEel - My point is that code doesn't exist in residential. I am not saying you cannot stack drywall - I do it all the time. I am saying if you do you are making it weaker especially ceilings.
    – DMoore
    Mar 20 '20 at 15:44

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