This may sound like a stupid question, but I only do drywall occaisionally. Is all 5/8″ drywall fire rated? I went to Lowe’s and the local lumber yard today to get some 5/8″ drywall specified by a customer for a small job and all that either one of them had was fire rated. It really didn’t make a difference to me, I was just wondering.
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Prescriptive codes don't address the connection at less common angles, so base the connection off more typical ones using bolts, structural screws, blocking, and steel tension ties.
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
> Is all 5/8" drywall fire rated?
Yep. Actually, all drywall is fire-resistant, and any thickness 5/8 or greater is thick enough to be used for some types of firewalls. That's really what they mean when they say it's "fire rated."
um... gotta disagree. there is typeX which has something added to it (fibers maybe) that adds to it's fire-rating. No type X equals little or no fire rating. why else would they sell both type x and non-type x 1/2 drywall board?
As to the OPs question as to wheather 5/8 non type x exists, I have no idea. All I have ever seen is 5/8 type X.
Your reply was somewhat ambigous (sp). I do agree all drywall provides some fire protection, but if it ain't rated, it ain't rated.
All 5/8" really all drywall has fire resistive properties but when the term fire rated is used it is generally used in the contex of a UL rated assembly. You can or used to be able to buy 5/8 with a regular core (slightly cheaper than the fire rated), you can buy it as type x and type C, both as I recall, have ratings for use in UL rated walls. I know the type C has fibers in it, not sure about the type X. When building a fire rated wall always use fire rated drywall. 1/2" is also available as firerated. The end of the rock tells you what type it is.
Edited 7/3/2007 11:25 pm ET by duckport
looks like we posted at the same time.
I agree.
You write better than me.
Better than I.
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
No better than him. You write well."Poor is not the person who has too little, but the person who craves more."...Seneca
I just make holes in drywall, but uh, isn't that "you write more weller than him" ?
Ya know, the pluperfect conjunctive (or would it be the past prefective conjunctivitis?)
CAP
No, it's much more gooder.
duckport is right ... and the real question is not is it fire-rated but is it considered non-combustible?
Regular drywall is NOT considered non-combustible, type X (or Firecode C) IS because of the glass fibers in the gypsum. Manufacturers such as USG and National make all of their 5/8" gypsum board Type X or Firecode C.
Jeff
The type X not only has glass fibers, but it is denser too ( this you notice when you try to lift a sheet, LOL) I think a lot has to do with what code they are trying to satisfy. are they looking for a twenty minute, a one hour, or an exterior grade one hour?<we all white well>
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
There are a variety of assemblies that can be used to create a wall that prevents fire spread. I reall once having to rock a wall with 1/2', tape it, then rock it a second ply with no adjacent seams or joints, then tape it again.
My more recent experience is that using typical 5/8" SR on the wall and cieling of a garage satisfies the need for fire separation when it is hung and taped in.
Firewalls between dwelling units in separate apartments require a bit more tho, and type X is called for, on both sides of the wall, with fire caulk at penetrations.
Type X is also used as an exterior sheathing for ccondo and other multiple housing situations where fire spread prevention is needed.
I even came across a specification for a three hour fire rating and two hour - the 3hr was for support column
Some "fire-rating"s are simple for lomitation of fire spread on surface, others are for limitation of heat penetrating the structure of the assembly. The former being to allow inhabitants time for escape, the latter to prevent collapse of a structure while fire-fighting efforts are underway.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
I forgot to ad the link where GP makes drawings and speccs for various assemblies availabele online in CAD and PDF formats
http://www.gp.com/build/pageviewer.aspx?repository=bp&elementid=3874&pid=6333&lastpid=1064
http://www.gp.com/build/PageViewer.aspx?repository=bp&elementid=3487
http://www.gp.com/build/bpsearch.aspx?q=fire%20rated%20wall%20assemblies
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
I was at a GP seminar one time and asked the speaker what exactly Type X refers to. He explained (and don't blame me if I have my compounds wrong) that regular gypsum is made with calcium hydroxide. Type X is made with calcium dihydroxide, which contains an eXtra water molecule which increases the fireresistance characteristics - more water water to boil, essentially.
So THAT is why it is so heavy to carry! I'm hauling an extra water molecule around, LOL
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
More than one, I'm guessing.
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
Well, yeah, ifin you wants to be picky about it;)but who's counting?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Gypsum is calcium sulfate. Lime is calcium oxide or calcium hydroxide.
You're absolutely correct. I don't get around the periodic chart much, but as much as wikipedia can be trusted...
Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O.
Yeah, I gotta confess to a brain fart, too. It was especially egregious in me since I've been known to mix DW into soil to take advantage of the calcium and sulfer in it.So. . . If anyone is using the numbers given in my previous post, they should substitute 1450*C anywhere I said 580*C. DW (Calcum Sulfate) decomposes at 1450*C.Everything else can stand as is. I hate it when I do that.SamT
Drywall is not necessarily fire rated just because it is 5/8 inch. Drywall can be non-fire rated in 5/8 inch, but it is probably something you'll never see.
All drywall is non-combustible, but not all drywall is fire resistant. When drywall is exposed to heat the gypsum core crumbles, though it doesn't burn. If you wanted a wall that would not burn, regular drywall is sufficient. But drywall is also used for walls that resist transmitting a fire from one side to the other. This is done by providing an insulating barrier that holds up to the heat for a considerable amount of time. So, fire resistant drywall is formulated differently so it does not crumble. This gives sufficient delay in the fire passing through the wall to meet certain standards.
Per wikipedia:
"When used as a component in fire barriers, drywall is a passive fire protection item, subject to stringent bounding. In its natural state, gypsum contains the water of crystallisation bound in the form of hydrates. When exposed to heat or fire, this water is vapourised, retarding heat transfer. Therefore, a fire in one room, which is separated from an adjacent room by a fire-resistance rated drywall assembly, will not cause this adjacent room to get any warmer than the boiling point (100°C) until the water in the gypsum is gone. This makes drywall an ablative material because as the hydrates sublime, a crumbly dust is left behind, which, along with the paper, is sacrificial. Generally, by increasing the layers of Type X drywall, the more one increases the fire-resistance of the assembly, be it horizontal, or vertical. Evidence of this can be found both in publicly available design catalogues on the topic, as well as common certification listings. "Type X" drywall is formulated by adding glass fibers to the gypsum, to increase the resistance to fires, especially once the hydrates are spent, which leaves the gypsum in powder form. Type X is typically the material chosen to construct walls and ceilings that are required to have a fire-resistance rating." [Emphasis added.]
With my mouth I will give great thanks to the Lord; I will praise Him in the midst of the throng. For He stands at the right hand of the needy, to save them from those who would condemn them to death.
- Psalms 109:30-31
Just to be a little picky with that Wikipedia entry and Teks' seminar speaker;Calcium hydroxide and calcium dihydroxide are the same thing, just different names.The water in CH doesn't boil off at 100*C. It does disassciate from the calcium at 580*C, this takes many more BTUs than simple boiling.The CH substrate in DW contains condensed vapor in the form of small groups of free (Non hydrated) water molecules. At 100*C the droplets boil like a miniature explosion breaking small chunks of CH loose from the greater mass. This is observed as crumbling and eroding, thus exposing a fresh surface. As soon as this new surface gets to 100*C it erodes away. Pretty soon, ya gots no fire barrior left.THe FG fibers in Type X hold those crumbs in place so they can continue to absorb BTUs and keep the temperature down to 580*C. It takes a LOT of BTUs to make CH go from 580* CH to 580* calcium and water, then the water molecule flashes to a steam molecule, which grabs a bunch more heat from the neighboring CH molecules, which the fire then has to replace before they in turn disassociate.SamT