National Gypsum Construction Guide - 12th Edition

Sound and Fire Rated Assemblies
SOUND RATINGS
Drywall and plaster construction
systems are laboratory
tested to establish their
sound insulation characteristics.
Airborne sound insulation
is reported as the
Sound Transmission Class
(STC), whereas impact
noise, tested on floor-ceiling
systems only, is reported
as the Impact Insulation
Class (IIC).
When selecting systems based
on laboratory performance
ratings, it should be clearly
understood that field conditions
such as flanking
paths, air leaks, etc. caused
by design or workmanship
can reduce acoustical performance.
For these reasons
National Gypsum
Company cannot guarantee
the performance ratings
of specific construction
assemblies erected in
the field.
To achieve maximum sound
isolation from an assembly,
published construction
details must be followed
completely. The use of
non-hardening, permanent,
resilient, acoustical sealant
is recommended to seal off
air leaks at floor, ceiling,
and partition or wall intersections.
In selecting a construction system
where sound isolation
is important it is necessary
to take into account the
building’s overall structural
design, openings, type of
occupancy, location and
background noise level.
The complexity of the proposed
system will necessarily
affect the final cost and
possibly the in-place
acoustical performance of
the system.
The national standard for airborne
sound testing, ASTM
E 90, measures the sound
transmission loss from 125
to 4,000 Hertz. It is measured
at 16 one-third
octave frequencies. The
data measured in ASTM
E 90 is then fitted to the
STC curve as is specified in
ASTM E 413. The STC
should not be compared
with FSTC values that are
obtained from field sound
transmission loss tests following
ASTM E 336 procedures.
The method used to
determine FSTC ratings is
different and cannot be
related to STC ratings
achieved by ASTM Method
E 90.
FIRE RESISTANCE
The term “fire-resistance”
designates the ability of a
laboratory-constructed
assembly to contain a fire
in a carefully controlled test
setting for a specified period
of time. Such an assembly
might be a partition, a
floor/ceiling, a roof/ceiling,
or a protected beam or column.
The degree that
assemblies put together and
tested under controlled laboratory
conditions retard
the spread of damaging
heat is measured in intervals
of time. For example, if
a construction assembly in
the laboratory adequately
contains the heat for two
hours and meets other
requirements during the
laboratory fire test, it is
given a two-hour fire resistance
rating.
Fire tests may be conducted at
any of several recognized
facilities. Partitions,
floor/ceilings, roof/ceilings,
beams and columns are
tested in accordance with
ASTM Standard E 119, Fire
Tests of Building and
Construction Materials.
Fire-resistance ratings are
based on full-scale tests
under controlled conditions
and are generally recognized
by building code
authorities and fire insurance
rating bureaus.
Requirements for fire-resistance
ratings are usually
assigned by local building
code officials based on the
expected occupancy of the
space. It is critical that you
review plans in the bid
stage to ensure that the
details drawn match the
referenced design numbers.
If the detail drawn does not
match the assembly design
number as listed in the
Gypsum Association Fire
Resistance Design Manual,
UL Fire Resistance
Directory, or Factory
Mututal Specification
Tested Products Guide,
contact the architect for a
clarification.
Fire-resistant ratings represent
the results of controlled
laboratory tests on assemblies
made of specific con-
8 NATIONAL GYPSUM SOUND AND FIRE RATED ASSEMBLIES
figuration. For that reason,
National Gypsum
Company cannot guarantee
the performance of specific
construction assemblies
erected in the field. When
selecting construction
assemblies to meet certain
fire-resistance requirements,
caution must be
used to ensure that each
component of the assembly
is the one specified in the
test. Further, precaution
should be taken that assembly
procedure is in accordance
with that of the tested
assembly.
For fire safety information, go to
www.nationalgypsum.com.
CONTROL JOINTS AND
ISOLATION DETAILS
Though most systems referred
to in this manual are nonload-bearing,
they need
structural consideration of
their ability to retain
integrity over a period of
time and be relatively rigid.
When other elements such
as doors, fixtures, cabinets,
etc., are affixed or joined to
a drywall or plaster system,
provision must be made to
ensure that these loads are
adequately supported.
Structural framing, completely
separate from the
system, may be necessary
to support eccentric or
heavy loads.
CONTROL JOINTS
Control joints are frequently
necessary to prevent cracking
in the gypsum board
and plaster systems.
Isolation should always be
considered where structural
elements such as slabs,
columns, or exterior walls
can bear directly on nonload-bearing
partitions.
Gypsum as well as other
building products and
materials are subject to
some form of movement
induced by changes in
moisture or temperature, or
both. To relieve the stresses
which occur as a result of
such movement, control
joints are required in both
partitions and ceilings.
Location of control joints is
the ultimate responsibility
of the design professional.
Control joints prevent
cracking in large areas of
gypsum board.
PARTITION CONTROL
JOINTS
In long expanses of partitions
such as corridors, control
joints should be used at
least every 30'. Door and
window openings create
stress points in partitions
and are recommended
locations for control joints.
Where jambs extend from
floor to ceiling and are
spaced not farther apart
than 30', no control joints
are required. When
“through-wall” control
joints are required in fire
rated assemblies, special
details are necessary which
are shown on page 96.
They are based on
Warnock-Hersey Report
WHI 651-0318.1.
CEILING CONTROL JOINTS
For large expanses of ceilings
with perimeter relief,
control joints must be
located a maximum of 50'
o.c. in either direction;
without perimeter relief,
30' o.c. maximum in either
direction. Control joints
should be installed where
framing or furring changes
direction.
PERIMETER CONTROL
JOINTS
Acceptable perimeter control
joints in systems do not
adversely affect fire or
sound ratings. The use of
perimeter control joints in
fire-rated assemblies is
described in UL Report
R-4024-7-8 and Factory
Mutual Report 16738.69.
REQUEST TEST COPIES BY
CALLING 1-800-NATIONAL
(1-800-628-4662).