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National Gypsum Company
Which Type of Drywall Is Most Fire Resistant?
There are three essential core types. Drywall comes in regular
core, Type X and Type C. All drywall affords some degree of
fire protection. After all, its rock, its water,
its difficult to burn. Regular drywall is fire resistant.
Its composed mainly of gypsum. Type X drywall contains
additional ingredients that enhance its fire-resistive properties.
The basic component added to Type X to give it superior resistance
is fiberglass. Finally, systems tested in the laboratory utilizing
Type C gypsum wallboard are the most fire resistant. The make-up
of Type C drywall is, generally, proprietary, but its fire
resistive properties are superior to Type X.
The most important characteristic of drywall, say fire officials,
is that it will not burn. Statistics show that in recent
years, fewer people have died in fires in the U.S.,
says the Gypsum Association. Naturally, there is no
single reason for the decline. But the diminished number has
a high correlation with the increased use of gypsum products
and other fire-resistant building materials, they say.
The gypsum in the core of the board actually emits
steam when exposed to fire and retards transfer through the
panel. This slowdown provides extra time to evacuate a room
Ask yourself this question, says Piccolo: How
do I know what type of drywall is being installed? Is it regular
drywall, Type X, or Type C? The drywall will be stamped if
it is Type X or Type C. The UL stamp on the back of
the gypsum wallboard Advises you if the board is Type X or
Type C in addition to letting you know that the wall board
is consistent in its construction, that you have quality,
and performance. Since the stamp will be on the back of the
drywall, you will have to inspect it prior to completion of
Navigating the UL Directory
Specification of fire-resistant gypsum systems starts at
the UL home page and becomes a relatively simple, essentially
cut-and-paste, web-based exercise that eliminates oversight
and provides the contractor with a detailed wall, ceiling
or floor configuration.
On the left-hand side of the UL home page (www.UL.com):
- Click on Certification.
- Click on Fire-Resistive Assemblies
- Click on Numbering System
for Fire Rated Assemblies.
Up comes a chart of fire-rated assemblies that becomes your
numeric guide to detailed specifications for walls, ceilings
and floor systems (Figure 3).
You will learn how to select a numeric code
that relates to the project detail in question by doing an
exercise later in this article. When the results page comes
up, click in the box under Link To File column
to view design detail.
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