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Old 01-30-2013, 01:42 PM   #1
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Is drywall considered non-combustible

Hello everyone- first timer here. I have searched the forums but can't seem to find an answer to this. I have a zero clearance gas fireplace (3 feet wide by 31 inches high) that was constructed with simple wood framing that was boxed out six inches from the wall (fireplace unit is in a pocket that projects beyond the foundation) and drywall to the ceiling. I plan to finish the drywall with 12 x 20 tile, a total of five feet wide, along the sides of the fireplace and to the ceiling over the fireplace. Even though it is zero clearance, the literature states that only non-combustible material should be used in the area 2 inches above the unit (the exact height of the standoffs). The vertical framing is tight to the sides and the horizontal header is tight to the standoffs, thereby two inches away.

My question is can this area be finished with drywall and then tiled? Is drywall (sheetrock, gypsum board, or whatever you want to call it) considered to be non-combustible? I have searched the internet and there seems to be contradicting opinions. I figured this forum would know the answer.

Thanks you for your help.

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Old 01-30-2013, 03:29 PM   #2
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The paper facing on drywall is not fireproof. While there is fire-rated drywall, (typically, 5/8" thick stuff) the fire rating is for burn through, not for scorching of the surface. Then, it's typically only good for maybe 1/2-hour at higher temperatures.

I think I'd want some sort of cbu on the wall, and even then, you'd have to be careful about the selection.
Jim DeBruycker
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Old 01-31-2013, 06:18 AM   #3
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Best answere I found

From a USG datasheet

In the National Fire Protection Associations 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 degrees C. The test exposes small samples of the material to a stream of air heated to 750 degrees C, (1382 degrees F). The material is deemed noncombustible if:

1) Sample temperatures at no time exceed 780 degrees C, (1436 degrees 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 degrees C, (1382 degrees 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 01-31-2013, 07:00 AM   #4
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Here, when fire is a consideration 5/8 fire resistant is used,all joints have a backing,like a 2x4,or metal stud,and a coat of fire resistant drywall mud is slapped over the whole face.

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Old 02-01-2013, 09:57 AM   #5
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We have decided that since the drywall is coming off the face of the boxed wood frame we are going to replace it with Dens Shield instead of drywall. That will solve the non-combustible issue. Thank you to everyone for your input. Much appreicated!!
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