JOINT TREATMENT UNDER EXTREME WEATHER CONDITIONS (GA-236-2000) Although extreme environmental conditions have little effect on the process of applying gypsum board, special procedures or precautions should be observed during the application and drying of joint compounds and adhesives. When weather conditions are extreme, either hot, cold, humid, or dry, the drying times of joint treatment materials are affected. Hot, dry weather accelerates drying; cold weather slows during 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 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 placement 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, Dry 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 help to eliminate drafts that can accelerate drying. Keep 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-type compounds for embedding tape because these materials have higher resistance to edge cracking caused by hot, dray 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 working 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 Weather, 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 cold and wet. Store joint tape and powder compounds in a dray area. In Cold Weather, provide heat. Joint treatment should not be applied to cold or damp surfaces. Where materials are being mixed and used to joint treatment or the laminating of one layer of board to another, the interior temperature of 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. Heathers should not be allowed to blow directly on 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 humidity 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.