![]() Painting a joint that has not dried properly can delay shrinkage by several weeks or even months resulting in delayed shrinkage. Once set, the joint will continue to shrink at a much reduced rate as the compound dries, and stop shrinking when dry. Setting compounds usually shrink back to a degree to ensure the joint tape is pulled back into the joint as it sets. They should not be used as a total system in a building that is being stopped in winter without heating. They have their place in heated premises or in warm / hot climates. In conclusion: think about the implications for total air drying systems before using them. This system generally works, however will also benefit if the house is heated. And because it?s thin, it will shrink less in relation to the entire joint. If the individual coats of a joint are not 100% dry prior to the next coat being placed, delayed shrinkage, caused by the moisture eventually drying out in warmer weather, will create hollow joints, shadow lines on joints, tram lines either side of the tape, etc.Ī thin coat of air drying compound on top of a plaster based coat will dry quicker than a thick coat. Doing this would eliminate most of the subsequent issues seen by both the stopping and painting industry, provided the workmanship by both parties is up to scratch. This cannot be achieved in winter without heating the building being stopped. It is unwise to use air drying compounds as a system, unless you are certain that each separate coat will dry, so that shrinkage is eliminated. Added to this, for cost reasons, most houses are not heated in winter during the finishing phases of construction. In New Zealand however, for at least 6 months of the year, the temperature is too low to enable a commercially acceptable time frame for drying of a thick coat of air drying compound. Warm air allows the thick taping coat of the air drying compound to dry (and shrink) in a reasonable time. These systems are common overseas in warm climates or houses that are heated during construction once closed in. Some air drying compounds are promoted as a total system, including the taping coat. If the air drying compound is not dry, it has not stopped shrinking. In winter there is increased risk of shrinkage during these colder months. Setting compounds dry quicker and are better suited in colder conditions as a first and second coat. During winter months or under cold damp conditions, drying rates can be improved using more but thinner coats of compound. Do not raise temperature above 18degrees celsius as other issues may arise. Use of a 1 x 2KW fan heater per 50m2 of floor space in a house is usually sufficient. Structures may require heating to achieve this temperature. Water, wet compound, air and surface temperature above 10☌ should be maintained until the compound is completely dry. Use back-blocking to significantly reduce the amount of load transferred to the joint If machine tools are being used, ensure the compound is being applied at the correct thickness garages, as the plasterboard will be hotter causing the compound to dry more quicklyĮnsure at least 0.5mm of compound is placed behind GIB® jointing tape, and coat the finished side of the tape with a thin layer of compound to slow evaporation under the tape, especially when using paper jointing tape Plaster ceiling joints located directly under the roofs early in the morning when the temperature is cooler, especially during summerīe wary of areas where insulation has not been placed in ceilings e.g. 90 minutes or less, duriong the summer months of November to April skillion roof on a hot day can create very high temperatures behind a joint) To avoid drying out before settling, Winstone Wallboards recommends the following:ĭo not use 150 minute set time compounds when the temperature exceeds 25-30☌ (in front or behind the joint, e.g. No compound placed over the tape immediately after bedding in of tapeĬompound is watered down or unauthorised retardants are added Inadequate compound placed under the tape Setting compounds must not dry out before their specified set time.ĭrying out before setting can occur due to a number of reasons, including: The symptoms of this are the compound will be soft, have little or no mechanical strength and adhesion, and the tape may bubble, crack or even fall out. the compound has dried before it sets, then the chemical setting process can not occur and cure the compound to achieve its required strength and adhesion. If the water content in the compound is lost or greatly reduced before the setting process starts, e.g. a 90 minute set product, actually starts to set after 90 minutes). This chemical setting occurs after the specified time for a compound (i.e. Setting Compounds require water to set hard.
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