Designation: C 1177/C 1177M – 08

Standard Specification for

Glass Mat Gypsum Substrate for Use as Sheathing1
This standard is issued under the fixed designation C 1177/C 1177M; 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 (´) indicates an editorial change since the last revision or reapproval.

1. Scope* 3.2.1 glass mat, n—a mat of glass fibers with or without a
1.1 This specification covers glass mat gypsum substrate, binder.
which is designed to be used as an exterior substrate for a 3.2.2 edge, n—the bound edge as manufactured.
weather barrier. 3.2.3 weather barrier, n—a material that prevents the pas-
1.2 The values stated in either SI units or inch-pound units sage of rain, sleet and snow.
are to be regarded separately as standard. Within the text, the 4. Materials and Manufacture
SI units are shown in brackets. The values stated in each
system may not be exact equivalents; therefore, each system 4.1 Glass Mat Gypsum Substrate shall consist of a noncom-
shall be used independently of the other. Combining values bustible water-resistant core, essentially gypsum, surfaced with
from the two systems may result in non-conformance with the glass mat partially, or completely embedded in the core.
standard. 4.2 Glass Mat Gypsum Substrate, type X (special fire-
1.3 The text of this standard references notes and footnotes resistant) designates glass mat gypsum substrate complying
that provide explanatory material. These notes and footnotes with this specification that provide not less than 1-h fire
(excluding those in tables and figures) shall not be considered resistance rating for substrate 5⁄8 in. [15.9 mm] thick or 3⁄4-h
as requirements of the standard. fire resistance rating for substrate 1⁄2 in. [12.7 mm] thick,
applied parallel with and on each side of load bearing 2 by 4
2. Referenced Documents wood studs spaced 16 in. [406 mm] on center with 6d coated
2.1 ASTM Standards: 2 nails, 1 7⁄8 in. [48 mm] long, 0.0915 in. [2.3 mm] diameter
C 11 Terminology Relating to Gypsum and Related Build- shank, 1⁄4 in. [6.4 mm] diameter heads, spaced 7 in. [178 mm]
ing Materials and Systems on center with glass mat gypsum substrate joints staggered 16
C 473 Test Methods for Physical Testing of Gypsum Panel in. [406 mm] on each side of the partition and tested in
Products accordance with Test Methods E 119.
C 645 Specification for Nonstructural Steel Framing Mem- NOTE 1—Consult manufacturers for independent test data on assembly
bers details and fire resistance ratings for other types of construction. See fire
C 1264 Specification for Sampling, Inspection, Rejection, test reports or listings from recognized fire testing laboratories for
Certification, Packaging, Marking, Shipping, Handling, assembly particulars, materials, and ratings.
and Storage of Gypsum Panel Products 5. Physical Properties
E 119 Test Methods for Fire Tests of Building Construction
and Materials 5.1 Specimens shall be taken from the samples obtained in
accordance with Specification C 1264.
3. Terminology 5.2 Specimens shall be tested in accordance with Methods
3.1 Definitions shall be in accordance with Terminology C 473.
C 11. 5.2.1 Flexural Strength—The specimens shall be tested face
3.2 Definitions of Terms Specific to This Standard: up and face down. The average breaking load shall not be less
than the following:
Method B

1
This specification is under the jurisdiction of ASTM Committee C11 on Load, lbf [N] Bearing Load, lbf [N] Bearing edges
Gypsum and Related Building Materials and Systems and is the direct responsibility Thickness, edges perpendicular to parallel to the substrate
of Subcommittee C11.01 on Specifications and Test Methods for Gypsum Products. in. [mm] the substrate edge edge
Current edition approved Sept. 15, 2008. Published October 2008. Originally 1⁄4 [6.4]
approved in 1991. Last previous edition approved in 2006 as C 1177/C 1177M–06. 50 [222] 40 [178]
2 ⁄ [11.1]
7 16 88 [394] 70 [314]
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 1⁄2 [12.7] 100 [445] 80 [356]
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM 5⁄8 [15.9] 140 [623] 100 [445]
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.

*A Summary of Changes section appears at the end of this standard.

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.

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 C 1177/C 1177M – 08
5.2.2 Humidified Deflection—Specimens shall have an av- the nominal thickness of 6 1⁄32 in. [6 0.8 mm], and with local
erage deflection of not more than the following: variations of 6 1⁄16 in. [6 1.6 mm] from the nominal thick-
Thickness, Humidified deflection, ness.
in. [mm] eighths of an in. [mm] 6.2.2 Width—The nominal width shall be up to 48 in. [1220
1⁄4 [6.4] not required
mm], with tolerance of 1⁄8 in. [3 mm] under the specified
⁄ [11.1]
7 16 3 [9] width.
1⁄2 [12.7] 2 [6]
5⁄8 [15.9]
6.2.3 Length—The tolerance in length shall be 6 1⁄4 in.
1 [3]
[6 6 mm]
5.2.3 Core, End and Edge Hardness—Specimens shall have 6.2.4 End Squareness—Corners shall be square with a
an average hardness of not less than 15 lbf [67 N] when tested tolerance of 6 1⁄8 in. [6 3 mm] in the full width of the
in accordance with Method B: substrate.
5.2.4 Nail Pull Resistance—Specimens shall have an aver- 6.3 Edges and Ends—The edges and ends shall be straight
age nail pull resistance of not less than the following when and either square, beveled, featured, tapered, or featured and
tested in accordance with Method B: tapered.
Thickness, Nail pull resistance,
in. [mm] lbf [N] 7. Finish and Appearance
1⁄4 [6.4] 40 [178] 7.1 Glass mat gypsum substrate shall be free of any cracks
⁄ [11.1]
7 16 70 [314] and imperfections that would render it unfit for its designed
1⁄2 [12.7] 80 [356]
5⁄8 [15.9] 90 [400] use.
5.2.5 Water Resistance—The three specimens selected shall 8. Sampling, Inspection, Rejection, Certification,
have an average water absorption of not more than 10 weight Packaging, Marking, Shipping, Handling, and Storage
% after a 2-h immersion.
8.1 Shall be in accordance with Specification C 1264.
6. Dimensions and Tolerances
6.1 Specimens shall be taken from the samples obtained in 9. Keywords
accordance with Specification C 1264. 9.1 core; exterior substrate; fire-resistant classification; flex-
6.2 Thickness, width, length and end squareness shall be ural strength; glass mat; glass mat gypsum substrate; gypsum;
determined in accordance with Test Methods C 473. hardness; humidified deflection; nail pull resistance; noncom-
6.2.1 Thickness—The nominal thickness shall be 1⁄4 , 7⁄16 , bustible; sheathing; substrate; type X; water resistance;
1⁄2 , or 5⁄8 in. [6.4, 11.1, 12.7 or 15.9 mm], with tolerances in weather barrier

APPENDIX

(Nonmandatory Information)

This Appendix gives general information and also suggestions for inclusions to be made elsewhere by the specifier. They are
not part of this specification.

The definitions of type X as given in 4.2 and the alternate definition given in this appendix, are intended only as a test to
define glass mat gypsum substrate for use as sheathing as meeting the requirements of type X. These tests do not indicate a
preferred application nor do they limit the use of the product in other fire related assemblies.

All gypsum panel products for which type X is defined, except gypsum lath and gypsum shaftliner board, use the same test
for type X products, therefore the type X designation indicates a consistent level of fire resistance.

X1. ALTERNATE DEFINITION FOR TYPE X

X1.1 Glass mat gypsum substrate, type X (special fire- [92 mm] deep non-loadbearing galvanized steel studs comply-
resistant) designates glass mat gypsum substrate providing a ing with Specification C 645 spaced 24 in. [610 mm] on center.
greater fire resistance than regular glass mat gypsum substrate The 5⁄8 in. [15.9 mm] thick glass mat gypsum substrate 48 in.
of the same thickness. Type X (special fire-resistant) glass mat [1220 mm] wide shall be attached using 1 in. [25 mm] long
gypsum substrate, when tested in accordance with Test Meth- drywall screws spaced 8 in. [203 mm] on center along the
ods E 119, shall provide the following minimum fire resistance edges and ends, and 12 in. [305 mm] along intermediate studs.
ratings for the assemblies described: All joints shall be oriented parallel to and located over studs
X1.1.1 One hour for a 5⁄8 in. [15.9 mm] thickness applied to and staggered on opposite sides of the assembly; and
a partition in a single layer application on each side of 35⁄8 in.

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 C 1177/C 1177M – 08
X1.1.2 Two hours for a 1⁄2 in. [12.7 mm] thickness applied studs and staggered on opposite sides of the assembly. The face
to a partition in a double layer application on each side of 21⁄2 layer 48 in. [1220 mm] wide shall be attached using 15⁄8 in. [41
in. [64 mm] deep non-loadbearing galvanized steel studs mm] long drywall screws spaced 12 in. [305 mm] along
complying with Specification C 645 spaced 24 in. [610 mm] on substrate edges, ends and along intermediate studs. Joints shall
center. The base layer 48 in. [1220 mm] wide shall be attached be oriented parallel to and located over studs, offset 24 in. [610
using 1 in. [25 mm] long drywall screws spaced 12 in. [305 mm] from the base layer joints, and staggered on opposite sides
mm] on center along substrate edges, ends and along interme- of the assembly.
diate studs. Joints shall be oriented parallel to and located over

SUMMARY OF CHANGES

Committee C11 has identified the location of selected changes to this specification since the last issue,
C 1177/C 1177M – 06, that may impact the use of this specification. (Approved September 15, 2008)

(1) Revised 6.2.3.

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