Cold and damp

The effect of cold and damp conditions on the drying time of joint compound under joint tape can readily be determined by examining the accompanying drying timetable. It is commonly acknowledged that hot, humid conditions-a temperature of 90 degrees F (32 degrees C) and a relative humidity of 90 percent, for example-will extend the drying time of joint treatment materials; however, it is not as apparent that cold, dry conditions also impact the same process. As an example, the table shows an identical extended drying time of 34 hours for two completely different conditions: 40 degrees F (4 degrees C) with 20 percent relative humidity and 80 degrees F (27 degrees C) with 80 percent relative humidity; these are typical winter and summer working conditions for many parts of the U.S. and Canada.

It is imperative that each coat of joint compound be thoroughly dry prior to the application of subsequent finishing and texturing materials. Materials should be applied in accordance with the manufacturer's instructions. A heavy application of compound or texture that will lengthen the drying time should be avoided.

The use of temporary heat systems to artificially increase the temperature of a working area should be accomplished judiciously. When a temporary heat source is used, the temperature in the artificially heated area should not exceed 95 degrees F (35 degrees C). Heaters should not be allowed to blow directly on wall surfaces as excessive local heat can cause joint compound to dry too rapidly resulting in localized cracking and delamination. In addition, some temporary heaters introduce large amounts of water vapor into the air and can cause high humidity conditions if the work area is not properly ventilated. Humidity conditions should be monitored to determine the impact on overall drying time. Areas using temporary heat systems should be well ventilated to prevent the build-up of fumes. Caution should be exercised when relocating heaters or heat sources.

Water-based joint treatment materials, such as ready-mixed joint compounds, should be protected against freezing while in storage. Partially frozen joint compound can be used as a bedding and second coat material, after it is allowed to thaw naturally and if it is thoroughly mixed prior to use. Previously frozen compound should never be used as a finish coat or topping material. Setting-type joint treatment materials provide an excellent alternative to canned or boxed joint compounds during cold weather as they can be stored in cold conditions and mixed at the job site. Water temperature should be closely monitored during the mixing process. Materials should not be mixed using extremely cold or partially frozen water.

Adhesion

Adhesives used for the application of gypsum board should be applied in accordance with manufacturers' instructions for temperature and climactic conditions. In general, adhesive application of interior gypsum board should be accomplished only when working area temperatures have been maintained at 50 degrees F (10 degrees C). Adhesives should be stored with conditions identical to those used with joint compounds as some adhesive materials can freeze. Previously frozen adhesive should be used only after discussion with the adhesive manufacturer.

Winter weather also introduces the possibility of snow, sleet, and rain storms. To prevent damage to gypsum board, it should be stored in a location where it is protected from moisture and properly supported above the ground. Board should not be enclosed in plastic shipping bags during storage. Plastic shipping bags are intended to provide protection during transit only and must be promptly removed upon arrival of the load. Failure to remove the shipping bag can increase the likelihood of developing conditions favorable to the growth of mold.

Care must also be exercised during cold weather installation of insulation to minimize the possibility of sag on interior ceilings and other horizontal soffit areas. When a polyethylene vapor retarder is installed on ceilings behind gypsum board, it is important to install batt or blanket ceiling insulation before the gypsum board is installed. When loose-fill insulation is used, the insulation should be installed immediately after the ceiling board is applied, but before the wallboard joints are taped or any other wet finishing operation has begun on the ceiling or adjacent walls. Failure to follow these procedures creates a potential for moisture condensation on the backside of the gypsum board.

Preventive measures designed to compensate for or minimize the effects of weather extremes can avert a potential problem. Preventive measures amount to little more than the conscientious observance of some common sense practices. Special attention to maintaining recommended environmental conditions before, during, and after applications of gypsum board and joint treatment materials are important factors in minimizing the effects of extreme weather conditions. Extreme weather conditions are less forgiving when good practices are not followed.