CoatingsPro Magazine

NOV 2018

CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.

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Page 23 of 76

COATINGSPRO NOVEMBER 2018 23 • Thermal Movement: Metal roofs are subject to significant thermal expansion and contraction during everyday temperature changes (+/- 1" per 100', or 2.5 cm per 30.5 m). Aluminum roof movement is even greater. Especially vulnerable are those roofs that have exposed structural fasteners (through-fas- tened roofs). Roofs where the panel runs (from eave to ridge) exceed 80 lineal feet (24.4 m) are especially at risk. Standing seam roofs that have thermally active clips are designed to allow movement and typically do not suffer from this same problem. If you observe bending or cracking, long run panels, slotting of fastener holes, torn-apart end laps, or other indicators of excessive movement, coating, despite its flexibility, will only hide the problem, and it will reoccur. • Penetrations: Roof-mounted equip- ment and pipe penetrations can be a constant source of problems in metal roofs, not only because they may have been installed incor- rectly but because of differential movement between the roof and the curb-mounted equipment. Coating may help leaking for a while, but the forces are huge and frequently need further attention. In general, elimi- nating or reducing roof-mounted items whenever possible is a good practice; complex flashing can be eliminated and foot traffic signifi- cantly reduced. It's also wise to never block the flow of water upslope from any curb; filling the area between the major panel ribs will cause water to pond on the roof, and metal roofs are never designed to have ponding water. • Additional Weight: Metal roofs are sensitive to additional weight. Look for indications of sagging of the purlins between frames or signifi- cant dimpling around fastener heads. Leaky or badly corroded fasteners can also result in corroded weak areas in the roof panels immediately around the fasteners. Re ad e r In qui r y at co ati n g sp ro m a m /i n q1118

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