Flat Roofing Specialist! Commercial Low-Slope Systems

Flat Roofer Association

November 1st, 2010 at 6:29 pm

Unlimited Thermal Movement – Wind Uplift

Unlimited Thermal Movement

All materials experience the stresses related to heating and cooling of the roof surface. In some cases, temperatures of a roof surface can vary by up to 200 degrees F throughout the course of a day. The term “unlimited thermal movement” describes designing a roof system to accommodate all of the expansion and contraction that a roof may experience throughout a 200 degree cycle. With a metal roof, this movement can be in the order of several inches. The Garland Standing Seam, one-piece clip design allows the metal roof panels to move freely through an unlimited range of expansion and contraction. Garland’s flat seam metal roof system, R-Mer Lite is also designed with the unlimited thermal movement concept.


UV Resistance

The ability of a roof top material to prevent degradation caused by exposure to Ultraviolet rays. Heat and UV are two primary causes of premature roof failure. UV rays cause the oils in a roofing membrane to dry out. These oils provide pliability and leads to the membrane cracking when they are dried out. The addition of unique polymer blends provides protection to the membrane from cracking by maintaining the membrane’s pliability. The resistance to UV degradation prevents membrane cracking which prolongs the waterproofing life of the membrane.


Wind Uplift

A wind uplift rating is not the miles per hour of wind speed a roof system can withstand, but rather, the negative pressure (pounds per square foot) that occurs when the inside air pressure of a building is greater than the air pressure outside the building. As wind passes over a building, there is a decrease in external air pressure on roof and some down wind surfaces. As this external decrease in air pressure occurs, there is a corresponding increase in air pressure differential between the inside and the outside of the building. As the internal air pressure tries to equalize itself with the external pressure, the resulting force, identified as wind uplift forces, attempts to lift the roof off the building. Most parts of North America require a 1-60 or 1-90 uplift resistance. Coastal regions and high wind areas may require additional uplift resistance.

Sources: The Garland Company, Inc.®

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