Long considered one of the more durable and sustainable
steep-slope roof covering materials, clay and concrete roof tile
products have been becoming more energy-efficient and
environmentally friendly. The development of lightweight and
cool-colored tiles has resulted in increased availability of tile
roof systems on existing structures and the use of tile roof
systems to achieve energy-saving goals.
To be classified as lightweight, tile roof covering material
must weigh less than 6 pounds per square foot (psf) at oven-dry
weight. A key factor in the design and performance of lightweight
tile roof systems is a tile's water absorption property. Water
absorption can increase a tile system's weight after a rainfall and
possibly affect a building's structural integrity. For example, a
tile product that weighs 5 psf at oven-dry weight and has a 10
percent water absorption rate by weight will weigh 6.05 psf when
wet.
A lightweight tile load of less than 6 psf allows tile to be
used as a roof system replacement on existing structures often
without requiring a structural load analysis per local building
departments. However, lightweight tile may sacrifice strength and
low water absorption properties to achieve the required light
oven-dry weight; therefore, the use of lightweight tile is not
recommended for all geographical areas. Locations where lightweight
tiles generally are not recommended include regions of freeze-thaw
cycling, moderate to heavy...
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