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Drop Drywall ceiling that meets code for 50db sound and 45minute fire?

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  • Drop Drywall ceiling that meets code for 50db sound and 45minute fire?

    Hello
    Fixing up an old triplex with sunk /crooked joists. Building code requires sound and fire standards. Currently the only "recommended" way is to put resilient channels on ceiling joists and 2 layers of drywall. Is there any other way to build a metal dropped ceiling that meets this code?

    thanks
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  • #2

    Re: Drop Drywall ceiling that meets code for 50db sound and 45minute fire?

    There are a few systems that would give you the fire and sound rating needed. However, these are usually for new construction where a concrete topping is used on the top of the floor. This is often not possible in an existing situation. The fire rating is not a problem, its the sound rating that is pushing you toward the resilient channels. I couldn't find any systems listed in the building code or manufacturers technical data that show a wood framed floor with no resilient channels giving the required ratings. (there might be something I didn't find) I suppose you could put steel studs/joists below the existing wood floor if there is enough headroom, but I don't see a big advantage over resilient channels, which would be easier and cheaper. There are specialty materials (insulation, drywall) meant to control sound transmission. These aren't usually noted in building code tables but might be permissible. If you do come up with a proposal you think might work you should discuss it with the building official before proceeding. He/she may have a suggestion.

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    • #3

      Re: Drop Drywall ceiling that meets code for 50db sound and 45minute fire?

      thanks. The code has a number of suggestions that all are based on resilient channels on the wood joists. However the joists are sagging so we do not want to attach ceiling to that. Thus suspended ceiling. Otherwise we would have to shim or sister the joists above first. Maybe there is an intermediate solution where you just shim under the resilient channels. But this starts to look like a drooped ceiling again. As for resilient channels, this is just a decoupling method not much different from simply building a double wall. The suspended ceiling in my mind would perform this function. With all the sagging foundation in the area there should be a solution!

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      • #4

        Re: Drop Drywall ceiling that meets code for 50db sound and 45minute fire?

        Talk to your building inspector that's what they are there for not just to give you a hard time. They have seen it all so will have some suggestions for your problem.
        Jerome
        Canada's South Coast

        Port Colborne On.
        CARPENTER noun. (car-pun-ter)
        1) A person who solves problems you can't.
        2) One who does precision guesswork based on unreliable data, provided by those of questionable knowledge. see also: wizard, magician.

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        • #5

          Re: Drop Drywall ceiling that meets code for 50db sound and 45minute fire?

          If the floor is so far out of level then a dropped ceiling does make sense. (You will want to make sure you have solved the sagging problem first) All of the fire/sound separations in the building code give specific construction requirements, so you can't mix and match. You have to follow the listing requirements. Steel stud/joists hung below the wood joist won't show up as a listed assembly. However, it will work as well if not better than a listed assembly using resilient channels. Just need to sort it out with your inspector first.

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          • #6

            Re: Drop Drywall ceiling that meets code for 50db sound and 45minute fire?

            Originally posted by Inspector Ron View Post
            If the floor is so far out of level then a dropped ceiling does make sense. (You will want to make sure you have solved the sagging problem first) All of the fire/sound separations in the building code give specific construction requirements, so you can't mix and match. You have to follow the listing requirements. Steel stud/joists hung below the wood joist won't show up as a listed assembly. However, it will work as well if not better than a listed assembly using resilient channels. Just need to sort it out with your inspector first.
            Thanks The sagging was stopped decades ago with repairs in the basement to prop up the structure, but not lifted to straighten. We are having the floors shimmed and I will be fixing the ceiling. I created a new post with a new solution.. Hoping it will fly!

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