Flat Ceiling Entryways, Exterior Ceilings & Soffits GlasRoc® Sheathing is a superior product for a flat ceiling entryway, exterior ceiling, or a soffit assembly, due to its ability to resist deteriorating effects of moisture and humidity.
The industry defines the amount of permissible sagging in a horizontal application as humidified deflection. There are several ASTM Standard Specifications that define a maximum allowable humidified deflection including ASTM C 79, ASTM C 931, and ASTM C 1177. Of these, ASTM C 1177 has the most stringent requirements. Note how GlasRoc® Sheathing performs.
Installation Recommendations for Exterior Soffits
Use GlasRoc® Sheathing in exterior soffit systems where weather-resistant performance is critical, including but not limited to, soffits with finished joints and soffits without insulation.
Install the product like a standard gypsum soffit board. Fasten the product to the framing members using the recommendations specified in GA-216 and ASTM C 840.
GlasRoc® Sheathing in Exterior Ceiling & Soffit Applications
Properties
12.7 mm (1/2") GlasRoc Sheathing
12.7 mm (1/2") Gypsum Soffit Board
15.9 mm (5/8") GlasRoc Sheathing Type X
15.9 mm (5/8") Gypsum Type X Soffit Board
ASTM TEST METHOD
Surface
Acrylic
Paper
Acrylic
Paper
N/A
Humidified Deflection (Sag)
1.6 mm (1/16")
22 mm (7/8")
0.4 mm (1/64")
13 mm (1/2")
C 473
Water Absorption % by Weight
<10%
40%
<10%
44%
C 473
Surface Water Absorption - grams
<1.6
2.0
<1.6
2.0
C 473
Referenced Standards
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ASTM C 514: Specification for Nails for the Application of Gypsum Board
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ASTM C 931: Standard Specification for Exterior Gypsum Soffit Board
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ASTM C 840: Standard Specification for Application and Finishing of Gypsum Board
•
ASTM C 954: Specification for Steel Drill Screws for the Application of Gypsum Panel Products or Metal Plaster Bases to Steel Studs from 0.33 in. (0.84 mm) to 0.112 in. (2.84 mm) in Thickness
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ASTM C 1002: Standard Specification for Steel Drill Screws for the Application of Gypsum Panel Products or Metal Plaster Bases
•
ASTM C 1177: Standard Specification for Glass Mat Gypsum Substrate for Use as Sheathing
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ASTM C 1397: Practice for Application of Class PB Exterior Insulation and Finish Systems
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CAN/ULC-S102 / ASTM E 84: Test Method for Surface Burning Characteristics of Building Materials
•
ASTM E 96: Test Methods for Water Vapour Transmission of Materials
