1、This document may be revised or withdrawn from circulation at any time.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 the most current edition of the document, access the Gypsum Association website at: www.g
2、ypsum.org. Printed in U.S.A. Copyright Gypsum Association 2013. All rights reserved. JOINT TREATMENT UNDER EXTREME WEATHER CONDITIONS (GA-236-13) Although extreme environmental conditions have little effect on the process of applying gypsum panel products, proper procedures must be observed during t
3、he application and drying of joint compounds and adhesives to ensure compliance with GA-216, Application and Finishing of Gypsum Panel Products. When weather conditions are extreme; either hot, cold, humid, or dry; the drying times of joint treatment materials are affected. Hot, dry weather accelera
4、tes drying; cold weather slows drying and increases the risk of freezing; wet or humid weather slows drying. Weather shifts from one extreme to another can cause movement in wood framing (moisture related) or in steel framing (temperature related) which can have an effect on the final appearance of
5、any given project. Preventive measures designed to compensate for or minimize the effects of weather extremes can avert a potential problem from occurring. Preventive measures amount to little more than the conscientious observance of some common sense practices. Special attention to the use and pla
6、cement of control joints and maintaining recommended environmental conditions before, during, and after application are all important factors in minimizing the effects of extreme weather conditions. Extreme weather conditions are simply less forgiving when good practices are not followed. In Hot, Dr
7、y Weather, work the shortest practical lengths of joint at a time to compensate for evaporation and the shorter workability time. Indoor humidity can be maintained by reducing ventilation and by keeping doors and windows closed; this can also help to eliminate drafts that can accelerate drying. Keep
8、 tools and the inner walls of joint compound buckets and containers wiped clean to prevent dislodging pieces of crusted compound thereby contaminating fresh materials. Use setting-type joint compounds with shorter setting times to minimize the effect of the “too-fast” drying conditions. Use setting-
9、type compounds for embedding tape because these materials have higher resistance to edge cracking caused by hot, dry weather. Rotate stocks of both powder and ready-mixed joint compounds to minimize the accelerated aging effect of hot weather. Avoid adding excess water to compounds to extend their w
10、orking times. The excess water will only increase shrinkage. Protect wet joints from rapid air movement which accelerates drying and causes fissures, checking, and edge cracks. Store bags of powder compounds out of direct sunlight; store containers of ready-mixed compounds indoors. In Wet, Humid Wea
11、ther, allow each coat of joint compound to thoroughly dry before the application of subsequent coats. Refer to Table 1 for specific drying rates rather than relying on moisture meters or visual observations to check for joint dryness. Select setting-type compounds, especially when conditions are col
12、d and wet. Store joint tape and powder compounds in a dry area. In Cold Weather, provide heat. Joint treatment should not be applied to cold or damp surfaces. Where materials are being mixed and used for joint treatment or the laminating of one layer of board to another, the interior temperature of
13、the room should be maintained at not less than 50oF (10oC) for 48 hours before and continuously until applied materials are thoroughly dry. When a temporary heat source is used, the temperature should not exceed 95oF (35oC) in any given room or area. Heaters should not be allowed to blow directly on
14、 wall surfaces. Excessive localized heating can cause joint compound to dry too rapidly resulting in cracking and localized delamination. Provide sufficient ventilation to ensure normal drying conditions. Certain temporary heaters introduce large amounts of water vapor into the air causing high humi
15、dity conditions, if not properly ventilated. Protect ready mixed joint compounds against freezing in storage. Use setting-type compounds to avoid many cold weather related problems.GA-236-13 2 TABLE 1 DRYING TIME - JOINT COMPOUND UNDER TAPE1Temperature, 0F (0C) Relative Humidity 32 (0) 40 (4) 50 (10
16、) 60 (16) 70 (21) 80 (27) 90 (32) 100 (38) 98% 53D 38D 26D 18D 12D 9D 6D 41/2D 97% 37D 26D 18D 12D 9D 6D 4D 31/4D 96% 28D 21D 14D 10D 7D 5D 3D 2D 95% 25D 17D 12D 8D 6D 4D 23/4D 2D 94% 20D 14D 10D 7D 5D 31/4D 21/4D 41H 93% 18D 12D 9D 6D 4D 23/4D 2D 36H 92% 15D 11D 8D 5D 3D 2D 44H 32H 91% 14D 10D 7D 4
17、3/4D 31/4D 21/4D 40H 29H 90% 13D 9D 6D 4D 3D 49H 36H 26H 85% 10D 6D 4D 3D 2D 34H 25H 18H 80% 7D 43/4D 31/4D 21/4D 38H 27H 19H 14H 70% 4D 3D 21/4D 38H 26H 19H 14H 10H 60% 3D 2D 42H 29H 20H 14H 10H 8H 50% 3D 2D 36H 24H 17H 12H 9H 6H 40% 2D 44H 29H 20H 14H 10H 7H 5H 30% 21/4D 38H 26H 18H 12H 9H 6H 4H 2
18、0% 2D 34H 23H 16H 11H 8H 5H 4H 10% 42H 30H 21H 14H 10H 7H 5H 3H 0 % 38H 28H 19H 13H 9H 6H 4H 3H 1For evaporation of 10 lbs (45.37 kg) of water per 250 ft (76.2 m) of tape, corresponding to 1/16“ to 5/64“ (1.6 to 2.0 mm) wet compound thickness under the tape. Thicker or thinner coats of compound will
19、 affect drying times in proportion to the wet compound thickness. These drying times apply when the exposed surface of the tape is bare or nearly bare, and when adequate ventilation is provided. A heavy coat of compound over the tape will lengthen the drying time. GYPSUM ASSOCIATION 6525 Belcrest Ro
20、ad, #480 Hyattsville, MD 20782 Phone: 301-277-8686 Fax: 301-277-8747 www.gypsum.org MEMBER COMPANY LIST 2013 AMERICAN GYPSUM COMPANY LLC CERTAINTEED GYPSUM CANADA, INC.CERTAINTEED GYPSUM, INC. CGC INC GEORGIA-PACIFIC GYPSUM LLC LAFARGE NORTH AMERICA INC. NATIONAL GYPSUM COMPANY PABCOGYPSUM a division of PABCObuilding products, LLC TEMPLE-INLAND UNITED STATES GYPSUM COMPANY
