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Gypsum Wallboard Quiz


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That all depends on what type of gypsum wallboard you are talking about.

Gypsum still has a flame and smokespread index like many other materials.

Some documentation lists a non-combustible material as one that will not ignite or flame within 5 minutes when places inside an oven at 1380 degrees F.

Even some of the best gypsum type X still states that it is not to be applied in areas that are subject to more then 140 deg F temperatures such as a wall for a wood stove.

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The Gypsum association has a Fire Resistance Design Manual. You can buy a copy or download sections or the whole thing for free at http://www.gypsum.org/GA60006.html . I doubt anyone here needs to read the whole thing, but section 1, starting at page 12 would be a good place to start.

I remember watching a good segment on TV a few years ago of a fire-rated wall assembly being tested along with a good explanation of what was happening, but I don't remember the show and can't find it online. Anyone?

My vote, FWIW, on the original question: (Paraphrasing Jeff) For our purposes, gypsum board, by itself, is a non-combustible material. Assemblies are a whole different beast.

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Hi All,

I think that the link that Bill K. posted is the clearest explanation of the issue. The question is flawed. The question really should have been two questions and should have been something like, "In the context of the building code, is gypsum wallboard considered a non-combustible material? In the context of the mechanical code is gypsum wallboard considered a non-combustible material?"

Answers would have been Yes and No respectively.



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Bill posted the bulletin I was going to post.

I don't believe the question is flawed at all. Here's my thinking:

98% of HI's know that gypsum can be used in fire separation walls and ceilings. Yes, there are different ratings for the type of 'assembly', but all in all, gypsum is the most common material used for separation.

I would guess more than 50% of HI's (or for that matter even builders) know you can't use gypsum as a fire/draft stop tight to a B or C vent. The quiz was thrown out there after I found another B vent going up a chase with gypsum tight to it.

I think it's easier to understand NOW than trying to make people understand the difference between building and mechanical sections of the code.

I think the bulletin (right from the NJDCA) explains it clearly.

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