Q: What kind of fire rating does plaster provide?
A:Portland cement-based plaster, commonly
called stucco, has long been and continues to be a popular choice
for finishes on buildings. It allows for a wide expression of aesthetics,
is a cost effective finish, is durable in all types of climates
(especially wet ones), and offers fire resistance. Fire resistance
is typically classified by a fire rating, but what kind of fire
rating does plaster provide?
Things that influence the fire rating of a plaster system include
the type of material used for the support member, the size of the
support member, the presence/absence and type of exterior sheathing,
the aggregate in the plaster mix, the presence/absence of insulation,
presence/absence of interior wall finishing materials (gypsum wallboard,
etc.) and the thickness of the section. The type of member—wall,
partition, ceiling, or other, and member classification (load bearing-LB
or non-load bearing-NLB)—also influences the rating.
In 1991, the Foundation of the Wall and Ceiling Industry published
a reference guide on portland cement-based plaster/stucco systems
used for fire protection, the Single
Source Document on Fire-Rated Portland Cement-Based Plaster Assemblies.
Designers, specifiers, building code officials, contractors, and
the general public are the intended audience. The information contained
therein is “not intended as design or installation criteria,”
but can help people determine how to assess their assemblies using
the referenced publications, fire test reports, industry standards,
For example, a typical residential application might be a 3-coat
system of plaster over 2x4 wood studs using metal lath attached
to the studs, either with or without a layer of sheathing, like
plywood. On the interior side would be a layer of gypsum board.
The detail for a system made with these components is assigned a
1-hour fire rating based on 1988 Uniform Building Code
of the Wall and Ceiling Industry is affiliated with the Association
of the Wall and Ceiling Industry. FWCI’s mission is to be
an active, unbiased source of information and education to support
the wall and ceiling industry. FWCI, is located at 803 W. Broad
St, Suite 600 in Falls Church, Virginia, 22046.
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