hamilton materials, inc. JOB CONDITIONS The Gypsum Association Recommendations and ASTM 0840 Specifications state that no drywall finishing shall begin until the interior temperature has been maintained at a minimum temperature of 50°F (10°C) for a period of 48 hours and thereafter until the compounds have completely dried. To our knowledge, no manufacturer of drywall finishing compounds recommends finishing drywall under lesser conditions. Unfortunately, the industry has not defined what "dried" or "dry" means. Logically, the terms are functions of the ambient conditions. It is also logical that the job conditions should not be 40°, 45°, etc., or that these water based compounds are "dry" after 24 hours at lower than recommended temperature. While some will assume that minimum temperature requirements are only for the benefit of manufacturers, that is not the case. These products do not develop the necessary bond and cohesion at lower temperatures. Unless used as recommended, they lack the properties necessary to resist cracking and bond failure, and will not provide a suitable surface for decoration. Published information on drying times at 50°F is as follows: at 0% humidity - 10 hours at 20% humidity - 23 hours at 40% humidity - 29 hours The contractor/applicator should be aware that these during times are applicable to each coat of material, and are based on maintaining a 50°F temperature with adequate ventilation to dispel humidity. Heating during the day while allowing colder temperatures during the night is not sufficient, and may in fact be detrimental. Thee is always a question as to who is responsible for job conditions. That question should be resolved at the bid/contract stage. If it is not, the sub-contractor is normally assumed to bear the responsibility. After all, most plans require the sub to apply materials in accordance with all codes, as well as specifications and recommendations of the manufacturer(s). In many cases the subcontractor is required by the general contractor to meet a production schedule which prohibits proper drying times. If a failure occurs, who is at fault? Why gamble? Why not have a complete understanding in your contract? When faced with a job problem caused by improper application conditions, the typical defense is "I've been doing it this way for 20 years and have never had a problem." Maybe that is true. But it is highly doubtful. Our responsibility as a manufacturer is to advise the user of our products how those products must be used to assure the desired result. In the case of job conditions, our recommendations coincide with all drywall industry recommendations.