Product Description

Cabot Gypsum Sheathing Board is a moisture resistant exterior wall sheathing that is intended for use behind cladding such as vinyl siding, brick/masonry veneer. The board has a core of non-combustible; dimensionally stable gypsum rock treated with a wax emulsion providing an enhanced moisture resistance. The core is sandwiched between dark brown face paper and brown back paper which is 100% recycled material. This produces a strong moisture resistant barrier which also provides wind and sound resistance. Although Cabot Gypsum Sheathing Board braces the framing and helps resist lateral forces of wind and vibration, it is not to be used for structural sheathing. Cabot Sheathing is manufactured in a 1/2" regular core and 5/8" Type X core as defined in ASTM C 1396 and suitable for use in noncombustible construction. 

Cabot Gypsum Sheathing Board may be used in EIFS (Exterior Insulation and Finish Systems) applications when specified by an EIFS manufacturer. It may also be used as a thermal barrier when used in a specified roofing application. 

Cabot Gypsum Sheathing Board is easily handled by one person and the score and snap cutting methods make it cost effective against plywood or wood fibre sheathing.


Product Specification

Cabot Gypsum Sheathing Board is manufactured to meet or exceed the requirements of ASTM C 1396 and CAN/CSA A 82.27 - M91 and Installation Standards ASTM C 1280.


Product Limitations

  1. Exposure to extreme temperature 52oC (125oF) should be avoided. 
  2. Store board for up to 1 month outside providing it is stored flat, off the ground, and have a protective covering. 
  3. Maximum stud spacing is 24" o.c.
  4. Should not be used as a nailing base. 
  5. Exterior cladding is to be fastened through the sheathing and into the wall framing with mechanical fasteners. 
  6. Not recommended for exterior ceilings or soffits. 
  7. Not recommended for use were long term exposure is an issue. A one month exposure time with unprotected board cannot be exceeded. Exposure for longer periods, material must be covered at the time of erection with a building felt or equal. The joints must be lapped and adequately fastened. 


Product Data

Surface Burning Characteristics: Flame Spread Rating of 20, Smoke Developed 0 per ASTM E 84.

Thickness: 1/2" (12.7 mm)

                5/8: (15.9 mm)

Width: 4' (1220 mm)

Lengths: 8' (2440 mm)

Edges: Square

Packaging: Two pieces per bundle, face-to-face and end taped.


Product Application

Cabot Gypsum Sheathing Board can be applied to wood framing with 1 3/4" (44 mm) galvanized roofing  nails or 1 1/4" (32 mm) type W bugle head corrosion resistant screws. The panels can also be fastened to steel stud using 1" (25 mm) Type S corrosion resistant screws and with special adhesives in combination with supplemental fasteners. All joints shall be loosely butted together, ends supported by framing and end joints to be staggered. Cabot Sheathing shall be applied horizontally or vertically to a maximum spacing of 24" in. (610 mm) o.c. Cabot Sheathing must be applied according to standards below. 

  • ASTM C 1280 Application of Gypsum Sheathing Board. 
  • CAN/CSA-A 82.31 Gypsum Board Application. 


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