1、GA-254-07 Copyright Gypsum Association 2007. All rights reserved. Printed in U.S.A. FIRE-RESISTANT GYPSUM SHEATHING (GA-254-07) Gypsum sheathing is manufactured with a water-resistive gypsum core and paper. It is a versatile, economi-cal, water-resistive sheathing. Gypsum sheathing is in-tended for
2、use as a substrate under exterior wall claddings in any climate. Gypsum sheathing is designed to be me-chanically attached to the outside surface of exterior wall framing spaced up to 24 in. (610 mm) o.c. using either nails, screws, or staples. Gypsum sheathing is manufactured in a wide range of len
3、gths to meet the demanding needs of the construction industry. Easily sized, cut, and installed, gypsum sheathing is the sheathing of choice wherever fire resistance ratings or noncombustible materials are required. Low material and labor costs are important economic ad-vantages gained by the use of
4、 this water- resistive sheath-ing. USES Gypsum sheathing can be used with virtually all ext e-rior wall claddings, including wood siding and shingles, panel siding, vinyl or metal siding, masonry or brick ve-neer, portland cement stucco, and Exterior Insulation and Finish Systems (EIFS).1 Mechanical
5、ly attached exterior wall claddings are at-tached through the sheathing and into the wall fra ming. Exterior Insulation and Finish Systems (EIFS) that incorporate gypsum sheathing are used with either me-chanical fasteners or adhesives for the application of the insulation, depending on the EIFS man
6、ufacturers recom-mendations. The performance of EIFS and recommenda-tions for the proper method of attachment are the sole re-sponsibility of the EIFS manufacturer and/or applicator. Fire Protection The natural noncombustible core of gypsum sheathing protects the framing from the hazards of fires oc
7、curring outside the building, even when covered by combustible siding. When exposed to high temperatures, chemically combined water in the gypsum is gradually released, pro-viding protection until all of its combined water is com-pletely driven off. In addition to its fire resistance proper-ties, gy
8、psum sheathing has a low flame spread rating2 of less than 25 as compared to a rating of 100 for red oak. Where fire -rated and/or sound control systems are desired or required, the test report or listing should be reviewed for complete information on systems and component parts used to achieve the
9、necessary fire or sound rating.3 Structural Integrity Racking tests have been conducted for the Gy psum Association by an independent laboratory according to ASTM Method E 72. Refer to Application of Gypsum Sheathing (GA -253) for details. Wall Bracing Building codes permit the use of vertically app
10、lied 4 ft. (1220 mm) wide panels of in. (12.7 mm) gypsum sheathing in place of continuous diagonal wall bracing. Shear Walls In areas where potential wind or seismic forces require shear walls to resist lateral forces, building codes provide allowable shear values for walls having gyp-sum sheathing
11、applied to wood fra ming. Specific values with construction requirements and limitations are con-tained in the building codes. Vapor Permeability Gypsum sheathing typically has an average vapor per-meance of 20 perms (dry cup method). This is well above the accepted minimum of five perms when the “U
12、” value of the wall is less than 0.25 and a vapor retarder not exceeding one perm is installed on the interior side of the framing and avoids a double vapor retarder condition. Code Compliance Gypsum sheathing complies with building code re-quirements for use as structural sheathing in frame con-str
13、uction. Consult the local building code for specific de-tails of construction and permissible shear values. STORAGE Gypsum sheathing shall be properly supported on a level platform and fully protected from weather, direct sunlight exposure, and condensation. Refer to Handling Gypsum Panel Products,
14、GA -801 for proper storage and handling requirements. 1 See Recommended Specifications: Application and Finishing of Gypsum Panel Products , GA 216, for exterior ceilings, soffits, and sills. 2 Tested in accordance with ASTM E 84 or CAN/ULC-S102 3 See the Fire Resistance Design Manual , GA -600, for
15、 specific system details. GA-254-07 Copyright Gypsum Association 2007. All rights reserved. Printed in U.S.A. GYPSUM ASSOCIATION 810 First Street NE, #510 Washington, DC 20002 202-289-5440 Fax: 202-289-3707 www.gypsum.org WEATHER PROTECTION Gypsum sheathing is designed for use as a substrate that is
16、 covered by an exterior wall cladding. Local weather conditions will dictate the length of time gypsum sheathing may be left exposed; however, it should perform satisfacto-rily if exposed to the elements for up to one month. The gypsum sheathing shall be covered immediately with a wa-ter-resistive b
17、arrier if exposure time will be extended or weather conditions will be severe. A weather-resistive barrier is required when sheathing is used in exterior portland cement stucco walls. For other specific weather resistive barrier requirements, consult the local building code or cladding manufacturer.
18、 Window and Door Openings To keep water out of the stud cavity, it is recommended that rough openings be properly protected by means such as flashing, weeps, or caulking. Avoid details that trap water and follow the window and door manufacturers recom-mendations for proper installation. DESCRIPTION
19、Gypsum sheathing manufactured to meet the require-ments of ASTM C 1396/C 1396M has the following char-acteristics: in. (12.7 mm) 5/8 in. (15.9 mm) Sheathing* Type X Sheathing* Width *4 ft (1220 mm) *4 ft (1220 mm) Standard Lengths 8 ft (2440 mm) 8 ft (2440 mm) Edges *Square *Square Surface Water res
20、istive Water resistive R-value 0.45 (RSI 0.079) 0.48 (RSI 0.085) * ASTM C 1396/C 1396M also covers other lengths and thicknesses. (Consult indi-vidual manufacturers for their product specifications. * Also available 2 ft (610 mm) wide with square or tongue and groove (T&G) edges. APPLICATION Gypsum
21、sheathing is to be installed in accordance with Application of Gypsum Sheathing, GA -253. This document may be revised or withdrawn from circulation at any time. The status of the document should be verified by the user prior to following any recommendations contained herein. To verify that you have
22、 the most current edition of the document, access the Gypsum Association website at: www.gypsum.org. Characteristics, properties, or performance of materials or systems herein described are based on data obtained under con-trolled test conditions. The Gypsum Association and its member companies make no warranties or other representations as to the characteristics, properties, or performance of any materials in actual construction.
