Build it to last

Understanding thermal movement in residential metal roof systems is key to long-term performance

Roofing contractors often are amazed at the time-tested craftsmanship of sheet-metal systems that are removed from historical structures. It's not uncommon for some of these systems to date to World War II. The one thing all long-lasting systems such as standing-seam, flat-lock and built-in gutters have in common is their ability to accommodate thermal movement. Unfortunately, when thermal movement is restricted, contractors may witness failures in as little as five years.

If you install metal roof systems on residential structures, it's important to understand the direction and effect of thermal movement on various metal types.

The basics

The principles of thermal movement can easily be misunderstood because anything that is not visible to the naked eye can be overlooked. For example, it's not likely for a roofing contractor to notice a 1/4-inch expansion in an aluminum panel. In addition, failures caused by thermal movement usually occur over dozens of thermal cycles or seasons, and the original installers or designers sometimes are not around to witness the failures. For that matter, a homeowner or building owner could have sold the property. In addition, failures associated with thermal movement often are misdiagnosed and blame is placed upon poor workmanship or improper soldering.

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