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My new house is still under construction, and for code reasons the builder is required to hang fire rated drywall on the ceiling of the basement.

I am sure the situation will arise eventually where I will need access to wire or plumbing runs behind this, and to do this I will need to cut the drywall.

Are there are any restrictions or things to know about according to national US residential building codes regarding the proper repair of fire rated drywall?

EDIT:

In case you were curious, the reason this fire board is code required is because the house wasn't built with typical dimensional lumber for floor joists. Instead they use these questionable looking Engineered I Joists

enter image description here

Because it is nothing but OSB in the middle, they don't quite as well in the event of a fire as dimensional lumber would. This is why the fire rated drywall is required.

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    Interesting. The last time we used those engineered joists, I don't recall any requirement to use fire rated drywall. I guess that's a local code.
    – BMitch
    Nov 2, 2012 at 13:32
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    @BMitch Maybe you are right, if so then this question is probably too localized or off topic. Nov 2, 2012 at 13:44
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    The code may be localized, but the question of working with fire rated drywall is a good one.
    – BMitch
    Nov 2, 2012 at 13:45
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    It might also be the combination of the engineered i beams and having a finished basement (I don't know if you are getting a finished basement). Pure speculation on my part.
    – auujay
    Nov 2, 2012 at 13:57

2 Answers 2

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I'm not aware of anything special for fire rating a joint in drywall, just use the same joint compound and tape you would use on the rest of your walls. Fire rated drywall will cut similar to normal drywall, but it will offer a lot more resistance because of the embedded fiberglass.

When sealing any gaps or cracks, they make special fire rated expanding foam and caulk. They tend to be orange in color. There's also fire rated insulation that can be used for any utility chases/bulkheads that connect to the ceiling.

For junction boxes, we've been required to box our in on common walls (2x4 above and below the junction and a piece of plywood behind everything) to ensure that any shorts in the electrical couldn't travel to another unit, but I doubt this would be a requirement for anyone in a single family home.

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    Ahh so thats what that dried orange foam is! Wasn't aware but good to know that they guys are doing everything to code. So to repair a rectangle hole, I would cut a piece of fire rated drywall and then seal it in place with this special foam and caulk? And only then I can tape and mud it? Nov 2, 2012 at 13:55
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    @maple_shaft You can caulk around the joint between the junction box and drywall. Between the drywall joints, just mud and tape like normal.
    – BMitch
    Nov 2, 2012 at 14:09
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    I see, in case I want to install overhead lighting some day. It will not be finished, but that may be something I take on some day when I get more money. Nov 2, 2012 at 14:42
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    @maple_shaft Pick your place and run the wiring and junction box for it now. You can cover it with a blank until you decide on the fixture.
    – BMitch
    Nov 2, 2012 at 15:07
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What is the code approved way to cut and patch fire rated drywall

There are several building codes that come into play for this question. You didn't specify your locality so I'll just assume you're in North America and that the most relevant code applicable to your question is National Fire Protection Association, NFPA 221.

In this case, I see no NFPA mentions for patching the drywall. That means following the code is, "per the manufacturers instructions." I checked the USG's installation instructions for normal and fire rated drywall and again see no difference in their patching instructions.

Drywall patching tips

Cut out a 2' square patch of drywall. It's so much easier to work with ample space. I usually center my cutout over a stud. You can use a magnet to find the fasteners in the studs. After cutting with a knife or drywall or oscillating saw, the 2' square patch can be pushed in on one side and the other side pops right out. Unless I'm trying to save the old drywall, I usually pull any fasteners through the old piece. Then remove the fasteners.

When finished working behind the drywall, find two pieces of scrap 1x3 or 2x4 furring that's a little longer than 2'. Center the furring inside the cut out hole so that half the wood is exposed and zap a few screws into that blocking. Now you've got a frame to set the new piece of drywall into.

Cut a new 2' square piece of drywall. You can cut the sheet of drywall into quarters at the store to make it easier to transport. Since your hole is 2' square, it's real easy to remember the exact dimensions. Slide the new square into place, fine tune the edge with a rasp if necessary, and zip a couple screws along the edges into that blocking and a couple more into the stud. Patch per the manufacturers instructions.

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