ASTM C964-88(2002)e1
(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 weather tightness 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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Designation:C964–88 (Reapproved 2002)
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.
This standard has been approved for use by agencies of the Department of Defense.
e NOTE—Changes were made editorially in January 2002.
1. Scope E 283 TestMethodforDeterminingtheRateofAirLeakage
Through Exterior Windows, Curtain Walls, and Doors
1.1 This guide covers the use of lock-strip gaskets in
Under Specified Pressure Differences Across the Speci-
compliance with Specification C 542 in walls of buildings not
men
over 15° from a vertical plane. The prime performance
E 330 Test Method for Structural Performance of Exterior
considerations are weathertightness against air and water
Windows, Curtain Walls, and Doors by Uniform StaticAir
infiltration, and structural integrity under wind loads. Included
Pressure Difference
are terminology, design considerations, and fabrication toler-
E 331 Test Method for Water Penetration of Exterior Win-
ances when using lock-strip gaskets in glazing applications.
dows, Curtain Walls, and Doors by Uniform Static Air
1.2 The values stated in inch-pound units are to be regarded
Pressure Difference
as the standard. The SI units in parentheses are for information
only.
3. Terminology
1.3 This standard does not purport to address all of the
3.1 Definitions—Refer toTerminology C 717 for definitions
safety concerns, if any, associated with its use. It is the
ofthefollowingtermsusedinthisguide:bite;compound;edge
responsibility of the user of this standard to establish appro-
spacer;elastomer;elastomeric;gasket;glazing;hardness;joint;
priate safety and health practices and determine the applica-
lock-strip gasket; open cell; seal; sealant; setting block; and
bility of regulatory limitations prior to use.
spacer. Additional elastomeric terms can be found in Termi-
2. Referenced Documents nology D 1566.
3.2 Definitions of Terms Specific to This Standard:
2.1 ASTM Standards:
2 3.2.1 clamping pressure—the pressure exerted by the lip of
C 542 Specification for Lock-Strip Gaskets
alock-stripgasketonmaterialinstalledinthechannelwhenthe
C 716 Specification for Installing Lock-Strip Gaskets and
2 lock-strip is in place.
Infill Glazing Materials
3.2.2 durometer—(1) an instrument for measuring the hard-
C 717 Terminology of Building Seals and Sealants
ness of rubber-like materials. (2) a term used to identify the
C 864 Specification for Dense Elastomeric Compression
relative hardness of rubber-like materials, for example, “low
Seal Gaskets, Setting Blocks, and Spacers
durometer” (relatively soft) or “high durometer” (relatively
C 963 Specification for Packaging, Identification, Ship-
hard).
ment, and Storage of Lock-Strip Gaskets
3 3.2.3 edge clearance—the distance between the bottom of a
C 1036 Specification for Flat Glass
channel of a lock-strip gasket and the edge of material installed
D 1566 Terminology Relating to Rubber
in the channel (see Figs. 1 and 2).
3.2.4 elongation—increase in length, expressed as a percent
of the original length.
ThisguideisunderthejurisdictionofASTMCommitteeC24onBuildingSeals
and Sealants and is the direct responsibility of Subcommittee C24.73 on Compres-
3.2.5 filler strip—see lock-strip, the preferred term.
sion Seal and Lock-Strip Gaskets.
3.2.6 flange—that part of a lock-strip gasket that extends to
Current edition approved Sept. 8, 1988. Published March 1989. Originally
form one side of a channel (see Figs. 1 and 2).
published as C 964 – 81. Last previous edition C 964 – 87.
Annual Book of ASTM Standards, Vol 04.07.
Annual Book of ASTM Standards, Vol 15.02.
4 5
Annual Book of ASTM Standards, Vol 09.01. Annual Book of ASTM Standards, Vol 04.11.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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C964–88 (2002)
A Hinge H Glass or panel
B Lock-strip I Bite
C Lock-strip cavity J Edge clearance
D Lip (sealing edge) K Frame-to-glass dimension
E Channel recess L Frame lug
FIG. 3 Gasket Systems
F Flange M Frame
GWeb
FIG. 1 Basic H-Type Gasket, its Functional Principles and
Nomenclature
3.2.14 lock-strip cavity—the groove in the face of a lock-
strip gasket designed to receive and retain the lock-strip (see
Figs. 1 and 2).
3.2.15 muntin—a secondary intermediate member in a
multiple-opening gasket system subdividing a glazed area.
3.2.16 reglet—agrooveorrecessformedinmaterialsuchas
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).
A Hinge H Glass or panel
3.2.19 structural gasket—See lock-strip gasket, the pre-
B Lock-strip I Bite
ferred term.
C Lock-strip cavity J Edge clearance
D Lip (sealing edge) K Frame-to-glass dimension
3.2.20 supported gasket member—a gasket member held in
E Channel recess L Spline
place by a supporting frame member.
F Flange M Reglet
GWeb
3.2.21 unsupported gasket member—a gasket member join-
FIG. 2 Reglet-type Gasket, its Functional Principles and
ing infill materials without being held in place by a supporting
Nomenclature
frame member.
3.2.22 vertical ladder gasket—a ladder gasket installed in a
vertical plane in such a way that the intermediate cross
3.2.7 H-gasket—See lock-strip gasket, and Fig. 1.
members (muntins) are horizontal members (see Fig. 3).
3.2.8 hinge—the minimum thickness of gasket material
3.2.23 web—that part of an H-type lock-strip gasket that
between the channel recess and the lock-strip cavity; the plane
extends between the flanges, forming two channels and that
at which bending occurs when the flange is bent open to
part of a reglet-type lock-strip gasket which extends between
receive or release installed material.
the flanges and spline (see Figs. 1 and 2).
3.2.9 horizontal ladder gasket—a ladder gasket installed in
3.2.24 zipper gasket—See lock-strip gasket, the preferred
a vertical plane in such a way that the intermediate cross
members (muntins) are vertical members (see Fig. 3). term.
3.2.10 ladder gasket—a lock-strip gasket in the form of a
subdivided frame having one or more integrally formed inter- 4. Significance and Use
mediate cross members (see Fig. 3).
4.1 This guide provides information and guidelines for the
3.2.11 lip—the inner face of the tip of a flange on a
design of lock-strip gasket glazing systems. For related stan-
lock-strip gasket (see Figs. 1 and 2).
dards, see Specifications C 542, C 716, and C 963.
3.2.12 lip pressure—the pressure exerted by the lip of a
lock-strip gasket on material installed in the channel when the
5. Comparison to Other Standards
lock-strip is in place.
5.1 Thecommitteewithjurisdictionoverthisstandardisnot
3.2.13 lock-strip or locking strip—the strip that is designed
aware of any comparable standards published by other orga-
to be inserted in the lock-strip cavity to force the lips against
material placed in the channel (see Figs. 1 and 2). nizations.
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C964–88 (2002)
DESIGN CONSIDERATIONS
6. General
6.1 Structural integrity and watertightness of a gasket glaz-
ing system is dependent on interaction of the several compo-
nents involved. These systems should be carefully designed
and built.
7. Components
7.1 The major components of lock-strip gasket glazing and
paneling systems are:
7.1.1 The supporting frame of metal, concrete, or other
structural building materials,
7.1.2 Lock-strip gasket, serving as an elastomeric mechani-
A Sharp arris (no radius) required
cal seal and as a retainer for panel or glass, and
B Nominal angle 6 2° tolerance
7.1.3 Glass or panel infill.
C Smooth surface required
7.1.4 The design of these components and their accessories D ⁄4 in. (6.35 mm) minimum
E Removable weakness membrane
are interrelated and the total system must be compatible.
F Flange provides smooth surface at lip
FIG. 4 Reglet-type Gasket in Concrete
8. Supporting Frames
8.1 Supporting frames are made of many materials, of
be solidly cast into the concrete without any voids or honey-
which the more common are aluminum, steel, and concrete.
combing at the leading edge of the flange because water could
8.1.1 Metal—Die marks, ridges, offsets, and scratches in
enter the interface between the flange and the concrete into
metal frames in contact with the gasket lips that could cause
which it is cast.An advantage of the flangeless reglet is that the
leakage should be avoided. Metal in contact with any part of
exposedjointbetweentheflangeandtheconcreteaswellasthe
the gasket should have sharp edges and burrs removed to avoid
cornerbuttjointsareeliminatedandthegasketlipsmakedirect
the possibility of damage to the gaskets that could result in
contact with the concrete frame. With this concept it is
structural failure through tear propagation. Weathering steel
essential to have a continuous smooth surface free of voids or
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
8.1.2 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
causeleakageandglassbreakageandsuchirregularitiesshould
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
8.1.2.3 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
8.1.2.1 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
8.1.2.2 Reglets—Itisessentialthattherecessintheconcrete
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
a removable weakness membrane as shown in Fig. 4. The
removable membrane maintains the proper recess shape and
keeps concrete out of the reglet while being cast. The remov-
able membrane can beT-shaped, when desirable, with the stem
projecting from the reglet to provide a more convenient means
of attachment to the formwork of the concrete panel. After
casting, the weakness membrane is easily removed. Plastic
reglets are available with flanges extending beyond the gasket
lips, providing smooth contact surfaces. An advantage of the
plastic flange is the provision of a smooth rigid surface for
contact with the gasket lip. The plastic flanges are butted
NOTE 1—Insufficient mass at A and relative long distance from B to
together at the corners requiring a joint which should be
lock-strip minimizes potential for adequate lip pressure at B.
properly aligned and sealed. The exposed plastic flange should FIG. 5 Gasket Mounting on Concrete Lug
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C964–88 (2002)
of pressure when excessive edge clearance permits the gasket
lips to slip to the narrower part of the lug. Unless the gasket
gripping the lug of a concrete frame has enough mass,
insufficient lip pressure against the concrete frame and leakage
could result because of the relatively large lug width.
8.1.3 Joints—Ideally, the best type of frame over which to
seat the gasket is one without joints. However, the realities of
construction should be recognized and dealt with. Watertight-
FIG. 7 Gasket Mounting Clearance
ness between the lock-strip gasket and frame depends on
unbroken pressurized contact. Joints in metal, unless welded
common are H-type and reglet type. Other special and propri-
and ground flush and smooth, make this concept difficult to
etary interlocking types have been developed as a result of
achieve. Members on either side of a butt joint should be
modifications to the basic types, usually because of provisions
installed as true to plane as possible. If the design relies upon
for mounting or mating to special framing members. Gasket
sealed metal-to-metal joints, the small void between the gasket
sections are generally of two types: the perimeter section and
lip and metal should also be sealed with a supplementary
the muntin section.
sealant. A recommended safeguard is to have a built-in
9.1.1.1 H-Type—The basic H-type gasket, its installation,
drainage system within the frame. In this way, any water
and nomenclature are illustrated in Fig. 1. After the gasket is
penetrating the frame joints or gasket to frame joints will be
installed over the frame and the glass or panel infill installed in
directed back to the outdoors. An aid towards minimizing the
the gasket, the lock-strip, which is of higher durometer, is
possibility of water penetration between the gasket and frame
forced into a groove in the gasket. A resultant compressive
at static (fixed, nonmoving) metal joints in single openings
force is transferred to the lips which apply pressure to the
may be seen in Fig. 6. The direction of the joint is horizontal
frame and glass. Sufficient lip pressure against smooth surfaces
between the horizontal and vertical members at the top of the
creates an effective weathertight seal. A wide selection of
frame, and vertical between the horizontal and vertical mem-
H-type gaskets are available that accommodate glass, panels,
bers at the bottom of the frame.
1 1
and frame lug thicknesses ranging from ⁄16 to 1 ⁄4 in. (1.6 to
8.1.4 Fr
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