Drywalling a garage with apartment above
I need all of you all’s viewpoint on something. We’re building a garage/shop with an apartment above. The local inspector is telling me I have to use 5/8″ fire-rated drywall on all of the interior walls below, and since I’m using manufactured trusses (with those gang-nail plates holding them together) that the ceiling of the garage/shop needs to be covered with either two 5/8″ fire-rated drywall layers, or one layer hung from resilient channel. He says the reasoning behind this part of the code (is it code?) is that the gang-nail plates will concentrate heat and fail, and using either two 5/8″ layers or a single layer held away from the trusses a bit will give more time before failure.
Have any of you heard of this requirement for living space above a garage or shop?
Replies
Don't know if it is code but sounds reasonable. 5/8" seems the way to go and the RC1 channel will allow you to get a good layout for the rock and lessen sound transfer
Mike
Trust in God, but row away from the rocks.
5/8ths is pretty much standard for attached garages. I've heard of doubled 1/2" requirements in lieu of 5/8ths, but building codes vary and can be superceded by local authorities if they feel the need for something more stringent is necessary.
I'd consider checking with truss mfg about the extra weight. Knowing your location may help to find someone who is familiar with your local building code,
"5/8ths is pretty much standard for attached garages. I've heard of doubled 1/2" requirements in lieu of 5/8ths, but building codes vary and can be superceded by local authorities if they feel the need for something more stringent is necessary. "The local authroities can't just superced the codes.However, the legislative body that approves which code to use can also add amendments to increase or decrease any requirements.But what can happen in cases like this is a dispute about whether this is commercial or residential application and then what part of the code applies.But an inspector can't just decide to add their own requirements..
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Bill,
"Local authorities" meaning the local town council or legislative body does have the right to add to(make more stringent) the code, but, you're right the inspector himself does not have the right to require something that is not part of the adopted/ammended code. This authority may vary from state to state, but my experience in the NorthEast is that locals may, at a minimum, increase the stringency of the code.
Geoff
Of course, the inspector has considerable latitude to "interpret" the code. But in a matter such as this there's usually little open to interpretation, save perhaps for whether this should be regarded as a business vs private garage area.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Isolating out the garage from the living quarters above is a really good idea. I've seen to many lax codes where this is concerned imo.
If the garage below is totally enclosed, then 5/8th (one layer) has been standard for a very long time, in most of US. All penetrations need be fire caulked(filled) and taped, door leading to living area needs be fire rated with the tags (manufacturer's)present, self closing and any HVAC ducting needs to be completely metal (22 gauge I believe is minimum).
This double layer thing sounds bogus to me unless each layer is something less than 5/8ths but, hey, some JHA have their own modifications. Go to your local library and get a copy of the code used in your area and see what is current in your area. Make sure your sheetrock is labeled as fire code compliant to and that side shows for inspection.
yes. It is fact based and reasonable.
Besides, our viewpoint is worht squat compared to his. None of us will be signing off on your permit
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so what he's saying is if you stick built this with joists and rafters, you can use ONE layer?
Be careful about the shop part. It may change the fire separation required. In our code it is considered a commercial occupancy and the separation is increased from that required between a house and its garage- both of which are considered residential occupancies.
Ask the BI what separation he requires (45 mins, 1 hr) and you can chose a variety of assemblies to satisfy it. I wouldn't have him making up requirements from what may just be his preferences.
"...the gang-nail plates will concentrate heat and fail..."
That's a popular myth, but isn't true.
But like Piffin said - It doesn't really matter what any of us think. You're gonna have to fght this on a local level if you don't want to do it.
It might be worth asking him if this is just his opinion, or if this is actually written in the code. If it's only his opinion you might have a good case for appealing it.
Thanks for all of your opinions, that is what I was looking for. I suspect this is his opinion, but I won't challenge him as we have a house to build after this and he can make my life difficult. And I have no fundamental problem with one layer of 5/8, just the additional of the channel. It will cost me another $300 and a couple hours. But he's the head dog around here and if you cross him, look out. This is not a show-stopper, I just wanted some other opinions. Thanks a ton, everybody. By the way, this project is in very far northern California, a few miles from the Oregon and Nevada borders, very rural. The nearest town with building materials is 75 miles away.
Smart move IMHO
As they say "pick your battles" I don't think this ones worth it.If you didn't have time to do it right the first time, how come you've got time to do it over again?
I did a lot of fire code commercial drywall work when I was a union carpenter. Double 5/8" FC rated is a standard for many applications, sometimes on both sides of a partition.
I'd go with the channel and the single 5/8" FC, and be happy that the inspector gave me that choice.
The channel has a lot of other advantages than just satisfying the AHJ.We use wood strapping. There is a lot of reduction in sound transmission, a reduction in vibration of the floor above, less telescoping of framing in the SR seams, and some other advantages that probably would not apply in your case.
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It's fairly standard now to require two layers of fireboard between garage and living space.
Hey guys. If the inspector says it is required, ask more questions and learn from it. Just cause inspectors say something, doesnt mean we all run in fear. I have always questioned the inspectors when they tell me about something I dont know and I have learned tons over the years.
Re. the drywall ceiling, pretty much all the codes I have ever read require some type of "fire separation" between garage and living space. (oh, by the way, the codes are for the safety and welfare of the inhabitants, so it makes a lot of sense to separate the areas so garage fires dont consume the room above before people have a chance to get out)
Anyway, you need to understand what building code your municipality inspects to.
All of the BOCA and CABO codes, if memory serves me, required a 1 hour fire separation between garages and living spaces.
You then need to reference Gypsum or other sheetrock companies fire separation assumblies books or find them online. (I have used National Gypsum in the past)
You then look for an assembly for a floor-ceiling application that gives you a 1 hour rating. (your inspector has already done this and is correct in saying 2 layers 5/8 typex or 1 layer with RC channel but you must insulate the cavity as well. You can then go thru the same process for the walls and will learn that 1 layer of 1/2 or 5/8 typex should be ok.
The IRC codes changed the requirements so if the jurisdiction uses the IRC codes (International Residential Code) then you only need 1 layer of 1/2". (it doesnt provide the same safety and I would be tempted to put up 2 layers of 5/8" but that is all the IRC code requires)
Regardless, I would invest the $50 in a code book and read up on it! I guarantee you will learn something. If you dont want to spend the money, ask to meet your inspector at his office so you can read his copy of the code book and maybe make a photocopy of the page.
Good luck
Additionally, 5/8" rock is generally preferred for ceilings, to prevent sag, and the double layer and/or channel will significantly reduce sound transmission.Note that requirements for ceiling are likely more stringent than for a wall, since heat/flames rise, and since failure of the ceiling/floor creates a more serious hazard than failure of a wall.Also, one should pay very close attention to air-sealing the ceiling and common walls, since, in addition to reducing the fire hazard and improving comfort, it will help reduce the carbon monoxide hazard. (But even given that the apartment above should have its own CO alarm.)
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
For the extra peace of mind and safety, why wouldn't you want to do two layers of 5/8"? Fire taped and fire stopped.
Is it such a large area that material and labor are that big a factor?
Maybe it's because I've done alot of commercial work where I've done walls rated 1, 2, 4 hours and higher. One hour on the ceiling between a garage and living space would be my minimum, irregardless of the code or inspector...buic