Is drywall combustible?

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Old 01-04-11, 05:42 PM
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Is drywall combustible?

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Originally Posted by NJ Trooper View Post
In addition to everything Mike said, fire code dictates that the flue pipe must be EIGHTEEN INCHES from any combustible material, and last I heard, drywall is combustible.
NJ, is drywall really considered a combustible in the code book? The reason I ask or question it is my building has been under a fire order for the last year and drywall is THE FIRE-STOP. (5/8" both sides of wall)
My understanding is drywall does not readily burn it lets the moisture trapped in the middle to escape cooling down the surface until there is no moisture left then the paper burns and the middle is nothing more then dust.
 
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Old 01-04-11, 05:49 PM
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Some drywall is more fire resistant than others. Type X or type C have improved fire resistance. You need to consult your local inspector about the requirements. Anything we post here won't trump local requirements.
 
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Old 01-04-11, 06:15 PM
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The gypsum material in standard drywall may not be directly flammable, but the paper/cardboard covering is. The 'fire-rated' forms that Mike speaks of have fibers embedded in the mix that causes them to PHYSICALLY hold up longer under exposure to flames. While the gypsum may not actually burn (and I'm not sure it won't?) but it certainly will crumble to pieces. 'Fire stops' are intended only to slow the spread of flame, giving building occupants the few extra minutes to escape that might mean the difference between life and death.

Also as Mike said, codes will always trump us.

I'm not 100% certain that NFPA considers drywall combustible, but I'm 'pretty sure'... in any case I would certainly be uncomfortable with drywall paper within an inch of my flue pipe! If there is indeed moisture in the gypsum, I'm sure that a few months of close exposure to a heat source would dry it out to the point that the paper could readily combust.

Now I'm headed out to the garage to see if I can burn some drywall!
 
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Old 01-04-11, 06:16 PM
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What is a fire order? 5/8" dry wall is considered fire rated. That doesn't mean fire proof, but provides a certain length of time that it resists fire. That enables people on the other side time to evacuate the area safely. Depending on requirements, the drywall may need to be double layered on each side to meet the burn time requirements.
 
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Old 01-04-11, 07:12 PM
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Interesting!

From a 2002 article

USG Data Sheet
Case Studies

In the National Fire Protection Association�s NFPA 101 Code for Safety to Life from Fire in Buildings and Structures, a noncombustible material is defined as a material that, "in the form in which it is used and under the conditions anticipated, will not aid combustion or add appreciable heat to an ambient fire." Materials are tested for noncombustibility in ASTM E 136 Standard Test Method for Behavior of Materials in a Vertical Tube Furnace at 750� C. The test exposes small samples of the material to a stream of air heated to 750� C, (1382� F). The material is deemed noncombustible if:

1) Sample temperatures at no time exceed 780� C, (1436� F).

2) There is no flaming after 30 seconds. 3) Once the sample loses 50% of its weight, there is no flaming and sample temperatures never exceed 750� C, (1382� F). ASTM E 136 is an extremely strict test and under its criterion, few building materials qualify as noncombustible. Two USG Interiors products which do are CERAMIC HERITAGE and most THERMAFIBER insulation products.

In regard to gypsum wallboard, the product's paper facing prevents it from passing ASTM E 136. However, because it does have a demonstrated ability to perform in fire rated assemblies, the NFPA has placed it in a special classification called limited-combustible This category distinguishes gypsum wallboard from other, more highly combustible products. To qualify as limited-combustible, a material must have a noncombustible structural base or core, a surface less than 1/8 in. (0.3 cm) thickness and a flame-spread rating of 50 or less.

This last requirement can be confusing because the three national model building codes, (ICBO's Uniform Building Code, SBCCI's Standard Building Code and BOCA's National Building Code), all allow composite materials that meet the NFPA�s definition of limited-combustible, to be classified as noncombustible.
 
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Old 01-04-11, 07:20 PM
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Originally Posted by drooplug View Post
What is a fire order?
Prior to buying the building I had the owner contact Fire life and saftey for an inspection. They are part of the Fire Marshall office of Ontario I believe. (could be wrong) They have enough power to make your life miserable and I did not want any surprises.

So a fire order is basically a deficiency list, of repairs that are needed to bring the building to today's code. In my buildings case

1) Fire doors on all apts, and separation between commercial and residential
2) Interconnected smoke alarms in all public and commercial areas with very loud bells
3) Sprinklers through out the building to act as a active fire stop between floors
4) Fire walls between differing units both residential and commercial

All to the tune of $150,000
 
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Old 01-04-11, 07:32 PM
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After my experiment in the garage, I'm going with the 'limited combustible' rating.

I took a scrap of drywall from the garbage can and hit straight on with the hottest part of my hottest torch for what seemed like 5 minutes.

Yes, the paper burned off with very little fanfare... then, the core material started glowing bright orange, almost yellowy orange (if that's a color?) and removing the torch there was no continued flame.

What's more, as HOT as the one side was, the other side of the 1/2" drywall was probably only about 110.

They could probably use this stuff for Space Shuttle tiles if it wasn't so heavy.

Myth ... BUSTED !

BUT, I would STILL trim that drywall away from that flue pipe! Because the paper DOES burn!
 
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Old 01-04-11, 10:17 PM
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I know on my attached garage, I had to use 'firestop' grade drywall. Memory is saying it was 3/4".. but maybe it was 5/8. I know I only lifted and screwed on one sheet to the ceiling from the scaffold before I went and rented a drywall lifter instead (almost broke my neck tryin to hold the first sheet up while screwing it in). The ceiling and adjoining walls had to be firestop grade.

For a wall pass-thru like that, Id be looking for a flange type of fitting for it. Get some metal and air between the hot pipe and the drywall paper for sure.
 
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Old 01-05-11, 02:51 PM
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Probably 5/8... but who knows? codes differ. Some places, in some applications, require TWO LAYERS!

Regular drywall is heavy enough, the X stuff is even heavier!
 
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Old 01-05-11, 03:56 PM
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Originally Posted by NJ Trooper View Post
Some places, in some applications, require TWO LAYERS!
That's what is required in many Chicago suburbs, and probably in Chicago itself. Also good for sound deadening.

And romex is totally forebidden.
 
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