Technical Documents

September 2016

The Gypsum Association has revised and updated 2 technical documents: GA-236, Joint Treatment Under Extreme Weather Conditions, and GA-253, Application of Gypsum Sheathing. Both documents are available for free download from the GA Bookstore as a service to the design and construction community.
    
For more than 15 years, GA-236 has provided special instructions for treating joints during weather extremes. Periodic revision of the document ensures that recommendations reflect current best practices. Very high or very low temperatures and humidity levels affect the drying times of joint compounds. Moreover, swings in temperature or moisture levels can cause movement in wood or steel framing. GA-236-2016 continues to offer common sense measures designed to mitigate problems associated with extreme weather.
    
New to GA-236-2016 is a graphic developed by the Drywall Finishing Council that illustrates joint compound drying times as a function of temperature at a specific relative humidity.
    
GA-253-2016, Application of Gypsum Sheathing describes proper methods of handling, storing, and applying a gypsum panel product type that is increasingly popular as a substrate for exterior cladding. With a water-resistant gypsum core and water repellent surface, gypsum sheathing is used under wood, aluminum, or vinyl siding as well as brick, exterior insulation and finishing systems (EIFS) and stucco exterior finishes. GA-253 clarifies fastener recommendations and better defines the appropriate water-resistant barriers for use in conjunction with gypsum sheathing.
    
Because gypsum sheathing frequently is specified as part of a fire-resistive system, GA-253-2016 mandates that construction details comply with systems tested by recognized testing facilities using ASTM E119 or CAN/ULC-S101 fire testing procedures. In addition, both fire-rated systems and sound-rated systems that incorporate gypsum sheathing must follow the requirements described in the GA-600, Fire Resistance Design Manual, now in its 21st edition.