ASTM C964-88(1997)
(Guide)Standard Guide for Lock-Strip Gasket Glazing
Standard Guide for Lock-Strip Gasket Glazing
SCOPE
1.1 This guide covers the use of lock-strip gaskets in compliance with Specification C 542 in walls of buildings not over 15 from a vertical plane. The prime performance considerations are weathertightness against air and water infiltration, and structural integrity under wind loads. Included are terminology, design considerations, and fabrication tolerances when using lock-strip gaskets in glazing applications.
1.2 The values stated in inch-pound units are to be regarded as the standard. The SI units in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: C 964 – 88 (Reapproved 1997)
Standard Guide for
Lock-Strip Gasket Glazing
This standard is issued under the fixed designation C 964; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope E 331 Test Method for Water Penetration of Exterior Win-
dows, Curtain Walls, and Doors by Uniform Static Air
1.1 This guide covers the use of lock-strip gaskets in
Pressure Difference
compliance with Specification C 542 in walls of buildings not
over 15° from a vertical plane. The prime performance
3. Terminology
considerations are weathertightness against air and water
3.1 Definitions—Refer to Terminology C 717 for definitions
infiltration, and structural integrity under wind loads. Included
of the following terms used in this guide: bite; compound; edge
are terminology, design considerations, and fabrication toler-
spacer; elastomer; elastomeric; gasket; glazing; hardness; joint;
ances when using lock-strip gaskets in glazing applications.
lock-strip gasket; open cell; seal; sealant; setting block; and
1.2 The values stated in inch-pound units are to be regarded
spacer. Additional elastomeric terms can be found in Termi-
as the standard. The SI units in parentheses are for information
nology D 1566.
only.
3.2 Definitions of Terms Specific to This Standard:
1.3 This standard does not purport to address all of the
3.2.1 clamping pressure—the pressure exerted by the lip of
safety concerns, if any, associated with its use. It is the
a lock-strip gasket on material installed in the channel when the
responsibility of the user of this standard to establish appro-
lock-strip is in place.
priate safety and health practices and determine the applica-
3.2.2 durometer—(1) an instrument for measuring the hard-
bility of regulatory limitations prior to use.
ness of rubber-like materials. (2) a term used to identify the
2. Referenced Documents relative hardness of rubber-like materials, for example, “low
durometer” (relatively soft) or “high durometer” (relatively
2.1 ASTM Standards:
hard).
C 542 Specification for Lock-Strip Gaskets
3.2.3 edge clearance—the distance between the bottom of a
C 716 Specification for Installing Lock-Strip Gaskets and
channel of a lock-strip gasket and the edge of material installed
Infill Glazing Materials
2 in the channel (see Figs. 1 and 2).
C 717 Terminology of Building Seals and Sealants
3.2.4 elongation—increase in length, expressed as a percent
C 864 Specification for Dense Elastomeric Compression
2 of the original length.
Seal Gaskets, Setting Blocks, and Spacers
3.2.5 filler strip—see lock-strip, the preferred term.
C 963 Specification for Packaging, Identification, Ship-
2 3.2.6 flange—that part of a lock-strip gasket that extends to
ment, and Storage of Lock-Strip Gaskets
form one side of a channel (see Figs. 1 and 2).
C 1036 Specification for Flat Glass
3.2.7 H-gasket—See lock-strip gasket, and Fig. 1.
D 1566 Terminology Relating to Rubber
3.2.8 hinge—the minimum thickness of gasket material
E 283 Test Method for Determining the Rate of Air Leakage
between the channel recess and the lock-strip cavity; the plane
Through Exterior Windows, Curtain Walls, and Doors
at which bending occurs when the flange is bent open to
Under Specified Pressure Differences Across the Speci-
receive or release installed material.
men
3.2.9 horizontal ladder gasket—a ladder gasket installed in
E 330 Test Method for Structural Performance of Exterior
a vertical plane in such a way that the intermediate cross
Windows, Curtain Walls, and Doors by Uniform Static Air
members (muntins) are vertical members (see Fig. 3).
Pressure Difference
3.2.10 ladder gasket—a lock-strip gasket in the form of a
subdivided frame having one or more integrally formed inter-
mediate cross members (see Fig. 3).
This guide is under the jurisdiction of ASTM Committee C-24 on Building
3.2.11 lip—the inner face of the tip of a flange on a
Seals and Sealants and is the direct responsibility of Subcommittee C24.73 on
Compression Seal and Lock-Strip Gaskets. lock-strip gasket (see Figs. 1 and 2).
Current edition approved Sept. 8, 1988. Published March 1989. Originally
3.2.12 lip pressure—the pressure exerted by the lip of a
published as C 964 – 81. Last previous edition C 964 – 87.
lock-strip gasket on material installed in the channel when the
Annual Book of ASTM Standards, Vol 04.07.
lock-strip is in place.
Annual Book of ASTM Standards, Vol 15.02.
Annual Book of ASTM Standards, Vol 09.01.
3.2.13 lock-strip or locking strip—the strip that is designed
Annual Book of ASTM Standards, Vol 04.11.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
C 964
3.2.15 muntin—a secondary intermediate member in a
multiple-opening gasket system subdividing a glazed area.
3.2.16 reglet—a groove or recess formed in material such as
concrete or masonry to receive the spline, or tongue, of a
reglet-type lock-strip gasket (see Fig. 2).
3.2.17 reglet gasket—See lock-strip gasket, and Fig. 2.
3.2.18 spline or tongue—that part of a reglet-type lock-strip
gasket which is designed to be installed in a reglet in
supporting material (see Fig. 2).
3.2.19 structural gasket—See lock-strip gasket, the pre-
ferred term.
A Hinge H Glass or panel
B Lock-strip I Bite
3.2.20 supported gasket member—a gasket member held in
C Lock-strip cavity J Edge clearance
place by a supporting frame member.
D Lip (sealing edge) K Frame-to-glass dimension
3.2.21 unsupported gasket member—a gasket member join-
E Channel recess L Frame lug
F Flange M Frame
ing infill materials without being held in place by a supporting
GWeb
frame member.
FIG. 1 Basic H-Type Gasket, its Functional Principles and
3.2.22 vertical ladder gasket—a ladder gasket installed in a
Nomenclature
vertical plane in such a way that the intermediate cross
members (muntins) are horizontal members (see Fig. 3).
3.2.23 web—that part of an H-type lock-strip gasket that
extends between the flanges, forming two channels and that
part of a reglet-type lock-strip gasket which extends between
the flanges and spline (see Figs. 1 and 2).
3.2.24 zipper gasket—See lock-strip gasket, the preferred
term.
4. Significance and Use
4.1 This guide provides information and guidelines for the
design of lock-strip gasket glazing systems. For related stan-
dards, see Specifications C 542, C 716, and C 963.
A Hinge H Glass or panel
B Lock-strip I Bite
DESIGN CONSIDERATIONS
C Lock-strip cavity J Edge clearance
D Lip (sealing edge) K Frame-to-glass dimension
5. General
E Channel recess L Spline
F Flange M Reglet
5.1 Structural integrity and watertightness of a gasket glaz-
GWeb
ing system is dependent on interaction of the several compo-
FIG. 2 Reglet-type Gasket, its Functional Principles and
nents involved. These systems should be carefully designed
Nomenclature
and built.
6. Components
6.1 The major components of lock-strip gasket glazing and
paneling systems are:
6.1.1 The supporting frame of metal, concrete, or other
structural building materials,
6.1.2 Lock-strip gasket, serving as an elastomeric mechani-
cal seal and as a retainer for panel or glass, and
6.1.3 Glass or panel infill.
6.1.4 The design of these components and their accessories
are interrelated and the total system must be compatible.
7. Supporting Frames
7.1 Supporting frames are made of many materials, of
which the more common are aluminum, steel, and concrete.
FIG. 3 Gasket Systems
7.1.1 Metal—Die marks, ridges, offsets, and scratches in
to be inserted in the lock-strip cavity to force the lips against metal frames in contact with the gasket lips that could cause
material placed in the channel (see Figs. 1 and 2). leakage should be avoided. Metal in contact with any part of
3.2.14 lock-strip cavity—the groove in the face of a lock- the gasket should have sharp edges and burrs removed to avoid
strip gasket designed to receive and retain the lock-strip (see the possibility of damage to the gaskets that could result in
Figs. 1 and 2). structural failure through tear propagation. Weathering steel
C 964
frames used in gasket installations should be coated to prevent honeycombing for the gasket lips to seal against because water
corrosion on the surfaces covered by the gasket to a line not could bypass the gasket lip and enter under it. Also important
less than ⁄8 in. (3.2 mm) beyond the lip edge when installed. is to have a sharp arris at the corners of the concrete frame so
7.1.2 Concrete—Gasket lips in contact with protrusions, that the corners of the gasket lip can properly contact and seal
crazing, form marks, and offsets on concrete surfaces could against the concrete. When plastic reglets are used, joints in
cause leakage and glass breakage and such irregularities should them could cause leaks unless sealed. When the gasket lips are
be avoided. Concrete frames for lock-strip gaskets should be in direct contact with the concrete, meticulous casting proce-
jointless and are more suitable when precast, as the tolerances dures and close surveillance are required to assure a proper
and smooth surfaces required are too exacting for cast-in-place finish along the contacting surface.
concrete. Special forms and meticulous casting procedures are 7.1.2.3 Frame Lug—It is difficult to achieve watertightness
required for optimum performance. with a gasket gripping the lug of a concrete frame as shown in
7.1.2.1 Corner Angles—Corner angles in the plane of the Fig. 5. Casting the lug to the 6 ⁄32-in. (0.8–mm) tolerance
glass should be held to 62° tolerance to properly receive the required is unrealistic when dealing with concrete. Also,
gasket lips. See Fig. 4. casting it without a tapered draft for ease of form removal
7.1.2.2 Reglets—It is essential that the recess in the concrete results in complicated form work. A tapered draft provides
be accurately cast so as to properly receive the spline of the poor control over gasket lip pressure and results in a reduction
gasket. This can be accomplished with a plastic reglet that has of pressure when excessive edge clearance permits the gasket
a removable weakness membrane as shown in Fig. 4. The lips to slip to the narrower part of the lug. Unless the gasket
removable membrane maintains the proper recess shape and gripping the lug of a concrete frame has enough mass,
keeps concrete out of the reglet while being cast. The remov- insufficient lip pressure against the concrete frame and leakage
able membrane can be T-shaped, when desirable, with the stem could result because of the relatively large lug width.
projecting from the reglet to provide a more convenient means 7.1.3 Joints—Ideally, the best type of frame over which to
of attachment to the formwork of the concrete panel. After seat the gasket is one without joints. However, the realities of
casting, the weakness membrane is easily removed. Plastic construction should be recognized and dealt with. Watertight-
reglets are available with flanges extending beyond the gasket ness between the lock-strip gasket and frame depends on
lips, providing smooth contact surfaces. An advantage of the unbroken pressurized contact. Joints in metal, unless welded
plastic flange is the provision of a smooth rigid surface for and ground flush and smooth, make this concept difficult to
contact with the gasket lip. The plastic flanges are butted achieve. Members on either side of a butt joint should be
together at the corners requiring a joint which should be installed as true to plane as possible. If the design relies upon
properly aligned and sealed. The exposed plastic flange should sealed metal-to-metal joints, the small void between the gasket
be solidly cast into the concrete without any voids or honey- lip and metal should also be sealed with a supplementary
combing at the leading edge of the flange because water could sealant. A recommended safeguard is to have a built-in
enter the interface between the flange and the concrete into drainage system within the frame. In this way, any water
which it is cast. An advantage of the flangeless reglet is that the penetrating the frame joints or gasket to frame joints will be
exposed joint between the flange and the concrete as well as the directed back to the outdoors. An aid towards minimizing the
corner butt joints are eliminated and the gasket lips make direct possibility of water penetration between the gasket and frame
contact with the concrete frame. With this concept it is at static (fixed, nonmoving) metal joints in single openings
essential to have a continuous smooth surface free of voids or may be seen in Fig. 6. The direction of the joint is horizontal
between the horizontal and vertical members at the top of the
frame, and vertical between the horizontal and vertical mem-
bers at the bottom of the frame.
7.1.4 Frame-to-Gasket Lips Clearance—Because lip pres-
sure is critical in resisting the passage of water, the design of
the supporting frame must allow at least ⁄8-in. (3.2-mm)
clearance between the installed gasket lip and any projecting
A Sharp arris (no radius) required
B Nominal angle 6 2° tolerance
C Smooth surface required
D ⁄4 in. (6.35 mm) minimum
E Removable weakness membrane
NOTE 1—Insufficient mass at A and relative long distance from B to
F Flange provides smooth surface at lip
lock-strip minimizes potential for adequate lip pressure at B.
FIG. 4 Reglet-type Gasket in Concrete FIG. 5 Gasket Mounting on Concrete Lug
C 964
be supported properly. The best performance can be expected
where the lug thickness equals or exceeds the thickness of the
glass or panel. There are exceptions to this recommendation
which are dependent upon other factors, such as lightweight
panels, extremely small openings, or situations where total
performance is not required. Acceptable deviations require
engineering analysis, consultation with the gasket manufac-
turer, and testing.
8.1.1.2 Reglet Type—The reglet-type gasket is a patented
type whose functional principles and nomenclature are illus-
trated in Fig. 2. Reglet-type gaskets are designed with a spline
that fits into a reglet. The seal against the frame is accom-
FIG. 6 Single-opening Metal Frame Joints for Increased
plished by forcing the spline of the gasket into the reglet so that
Watertightness
the fins on the side of the spline retain the gasket in the reglet
and thus hold the sealing lips of the gasket tightly against the
flanges or fillets. This allows the lips to exert unre
...
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