For exterior painting and coating systems on commercial construction projects, leading building product manufacturers (BPMs) such as The Sherwin-Williams Company and many others offer requirements for and recommendations on the proper environmental and weather conditions, during: first, delivery, storage, and handling; second, project conditions; third, examination; fourth, installation; fifth, drying and curing.
Five stages of proper environmental and weather conditions for exterior painting and coating systems
- Delivery, storage, and handling
- Project conditions
- Drying and curing
Protect materials from freezing, maintain a dry storage area
Delivery, storage, and handling. First, exterior painting and coating system manufacturers provide instructions as to how to store materials in areas within the acceptable temperature ranges, and to protect materials from freezing. Further, when handling materials, it is important for contractors to maintain a dry storage area, and protect materials from rain and other precipitation events, to prevent contamination or damage to the exterior coatings.
Environmental conditions to achieve optimal outcomes
Project conditions. Second, exterior painting and coating system manufacturers recommend that contractors maintain environmental conditions (temperature, humidity, etc.) within the recommended limits for each painting and coating system in order to achieve optimal outcomes. Under no circumstances can a contractor apply painting and coating under environmental conditions outside of the manufacturer’s absolute limits!
Surfaces must be dry to ensure good adhesion
Examination. Third, contractors cannot begin application of exterior painting or coating until substrates are properly examined and prepared. If the contractor identifies unsatisfactory conditions, it is important to notify the architect before proceeding. For example, surfaces must be dry to ensure good adhesion. Wet or damp surfaces, from rain, humidity, dew, frost, fog, and other environmental moisture, can compromise the installation.
No exterior painting or coating immediately after a rain event
For example, in 09 91 13 Exterior Specification, Commercial Painting Specification Guide, The Sherwin-Williams Company recommends no exterior painting or coating immediately after a rain event, during a fog event, when a rain event is forecast, or when a low temperature event is below 50°F — unless the exterior painting and coating systems are designed specifically for each of the environmental conditions and weather conditions.
Do not apply exterior painting and coating systems to wet or damp surfaces
Installation. Fourth, manufacturers recommend that contractors do not apply exterior painting and coating systems to wet or damp surfaces. For example, after a low intensity or high intensity rain event, or after dew, frost, or fog events, suspend work and wait until substrates are completely dry — block, concrete, cement composition siding / panels, drywall – exterior, exterior composition board (hardboard), wood, and other substrates.
Avoid environmental and weather impacts during the first 16 to 24 hours of curing
Drying and curing. After installation and during the early stages of drying, exterior painting and coating systems are sensitive to rain, high humidity dew, frost, and fog events and moisture condensation as a result of environmental and weather conditions. Accordingly, contractors need to plan exterior coating and painting schedule activities and work results in order to avoid environmental and weather impacts during the first 16 to 24 hours of curing.
More in the next blog post about weather-enabled decision support, weather safety and weather risk management for the construction industry and built environment…
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