Note: Descriptions are shown in the official language in which they were submitted.
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CONVENTIONAL FIRE-RATED ONE-SIDED CONSTRUCTION
BACKGROUND OF THE INVENTION
The invention relates to building structures and, in
particular, to a fire resistant membrane.
PRIOR ART
Mechanical shafts, chases, and stairwells are examples of
interior building areas requiring fire rated wall or ceiling
membranes. Frequently, such areas have access for their
construction available at only one side of the wall or
membrane. Known methods and materials for constructing these
restricted access membranes can be limited in their
effectiveness in achieving satisfactory fire resistance.
SUMMARY OF THE INVENTION
The invention provides an effective fire rated membrane
construction for walls, ceilings, mechanical shafts, chases,
and like structures that can be assembled from one side of the
membrane. The construction uses a novel combination of
conventional sheet metal framing elements, fire rated
wallboard or drywall sheets, and assembly techniques. A layer
of the fire rated drywall sheets is secured to light gauge
steel "C" studs or like framing elements. A second fire rated
drywall layer and optional successive layers is/are separated
from the preceding layers by resilient channels or like
elements. The channels are oriented at right angles to the
studs. The channels allow the successive drywall sheets to be
secured with screws that do not penetrate the assembly and,
therefore, do not directly transfer heat from one side of the
membrane to the other. The air space between layers
advantageously retards heat transfer from one layer to another
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thereby adding to the fire rating capacity of the membrane.
The channels, additionally, serve the important function of
laterally stabilizing the studs against excessive buckling
when they are subject to thermal expansion and their ends are
constrained. This stabilizing function can avoid the prior
practice of leaving the stud ends spaced from one another or
from a receiving track to accommodate thermal expansion and
thereby avoid buckling but, unfortunately, limiting the height
of the membrane.
The inventive construction is scalable in the sense that
additional protection can be obtained by adding layers of fire
rated wallboard with or without intervening channels.
The terms wallboard and drywall are used interchangeably
in the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary perspective view of a one-sided
fire rated wall membrane constructed in accordance with the
invention;
FIG. 2 is a fragmentary plan view of the wall of FIG. 1;
FIG. 3 is a fragmentary side elevational view of the wall
of FIG. 1;
FIG. 4 is a fragmentary perspective view of a resilient
channel used in the construction of the wall of FIG. 1; and
FIGS. 5A, 5B, and 5C represent optional alternative
bracing arrangements for a wall embodying the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A membrane or wall such as shown at 10 in the FIGS. is a
"one sided construction" meaning that it is assembled by a
person or persons standing or otherwise situated on only one
side of the membrane. Such one sided construction can be
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necessitated by certain building areas and/or conditions that
limit access to one side of the membrane. Examples of these
situations are high rise elevator shafts, utility shafts,
chases and reconstruction where the rating of an existing wall
is unknown. The membrane or wall 10 includes sheet steel "C"
studs typically made of light gauge stock and fire rated
gypsum wallboard sheets 12. The studs 11 are conventional
commercially available items as are the fire rated drywall
sheets 12. Typically the drywall sheets are of a thickness of
5/8 in. and are available in a 4 ft. width and lengths of 8,
9, 10, 12, 14 and 16 ft. The studs 11 can be any commercially
available unit typically ranging from 1-5/8 in. to 6 in. in
width and ranging in length, for example, between 8 ft. and 16
ft. Dimensions used herein can be substituted with industry
metric equivalents. The term membrane, as used herein,
comprehends a wall, ceiling or other like structure. Where
the membrane serves as a ceiling such as in a corridor or
stairwell, the studs 11 can serve as joists. The studs 11 can
be used in vertical and horizontal orientations to frame a
fire resistant chase or other structure.
The membrane 10 is ordinarily assembled by locating the
studs 11, in conventional upper and lower U-shaped tracks (not
shown) if it is to be a wall, in parallel relation on 2 ft.
centers, for example. FIGS. 5A, 5B, and 5C illustrate
optional conventional ways of bracing the studs 11 using a
bridging member between adjacent studs 11. FIGS. 5A and 5B
illustrate an elongated channel 16 fixed with screws 17 to
successive studs.
The construction of FIG. 5A utilizes small clip angles 18
attached to aligned holes 19 in the webs of the studs 11. In
FIG. 5B, a channel 16 is screw-attached to a flange of each
stud 11. In FIG. 5C, a flat strap 22 is screw-attached to the
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stud flanges. A short section of track 23, known in the
industry, shown in FIGS. 5B, 5C, is boxed in and screw-
attached to a pair of adjacent studs 11. A similar track
section 23 can be used at the ends of a wall and on, for
example, 8 ft. centers. It will be appreciated that screw
fasteners 17 used with the channels 16 or strap 22 and the
track 23 can be driven by a person on a side of the studs 11
away from the channel or strap.
After any bracing 16 or 22 and 23 to be used is
installed, the studs 11 are covered with a first layer 24 of
the fire rated drywall. The layer 24 is attached to the studs
11 with conventional self-drilling drywall screws driven
through the wallboard into the sides or flanges of the studs.
Thereafter, elongated sheet metal channels 26, preferably of a
type called a resilient channel and illustrated in FIG. 4, are
installed over the first layer 24. The channels 26 are
oriented horizontally so that they are perpendicular or cross
wise relative to the stud 11. The channels 26 are typically
installed on 2 ft. centers. As illustrated in FIG. 4, a
channel 26 has a web 27 and opposed divergent sides 28, 29.
One of the sides 28 is relatively wide and, preferably, has
oblong apertures 31 spaced along its full length. The
longitudinal edge of the apertured side 28 distal from the web
27 has an associated flange 32 oriented in a plane parallel to
the web 27. In a free state of the resilient channel 26, the
shorter channel side 29 is spaced from the plane of the
flange. The channels 26 are fastened to the studs 11 by
drywall screws 33 driven through the flanges 32 and wallboard
11 into the sides of the studs.
A second layer 34 of wallboard 12 is installed over the
resilient channels. Drywall screws 36 fastening the wallboard
12 to the channels 26 are driven into the web 27 of the
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channel preferably at locations remote from the studs 11. The
length of the screws 36 is adequate to penetrate and hold onto
the channel web 27 but insufficient to fully penetrate the
first wallboard layer 24.
5 The described membrane construction 10 affords many
benefits towards a high fire rating and greater utility over
prior art arrangements. Since none of the screws retaining
the layers 24 and 34 penetrate the full thickness of the
membrane 10, there is no direct heat conducting path from one
side of the membrane to the other and which would create a hot
spot to initiate a fire in a combustible. The channels 26,
being fixed in cross relation to the studs 11, serve to brace
the studs against buckling forces. This function allows the
ends of the studs to be assembled tight against the ends of
other studs or tight within runner tracks (top and bottom)
without gaps for thermal expansion and thereby increase the
limiting height. Ends of the studs tight fitted in runner
tracks can be screw attached to both runner track legs
(flanges) to increase the vertical load capacity of the
construction thus further raising the limiting height of the
construction. It is expected that this tight end fitted screw
fastened construction with heavier gauge studs can be used in
load bearing walls when restricted to "Exposed to Fire on
Gypsum Board Face Only" applications.
The air space, designated 39, between the wallboards 12
of the layers 24 and 34 serves as an insulator to reduce heat
transfer from one board to the other. The perforations 31 in
the channel side 28 allow air circulation over and through the
channels 26 and reduce direct heat transfer through the
channel side 28 from one wallboard to the other.
The illustrated membrane 10 can be supplemented in its
fire rating. Depending on the application, another series of
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channels 26 can be mounted on the second layer 34 in the same
manner as the illustrated channel 26 and a third fire rated
wallboard can be fixed to this second series of channels 26.
Again, it is important that the length of the screws be
selected so as to not penetrate the full thickness of the
membrane. Alternatively, for lesser requirements, a third
layer of fire rated wallboard can be simply applied directly
against the second layer 34. In these and other construction
variants, it is important that none of the screws extend
through the exposed surfaces of wallboard on both sides of the
membrane.
It should be evident that this disclosure is by way of
example and that various changes may be made by adding,
modifying or eliminating details without departing from the
fair scope of the teaching contained in this disclosure. The
invention is therefore not limited to particular details of
this disclosure except to the extent that the following claims
are necessarily so limited.
