5 Enemies of Your Roof Part 4: Expansion and Contraction


Just like our joints can get achy during the changing of seasons, your roof also experiences the woes of hot and cold. While expansion and contraction is related to the weather, its affects are tied more to roofing products behavior when exposed to varying temperatures.

As roofing technology advances, it has become apparent that using the same type of materials as much as possible creates a more cohesive system. Metal valley lining was the norm but now good roofers have transitioned to using an asphalt based liner for valleys, called Ice and Water shield. While these advancements are beneficial, there’s no way around using metal products in tandem with asphalt shingles. Wall flashings, nails and wood decking are essential to provide the rigid structure necessary to hold down and support malleable asphalt products.

It’s still a good system, but it isn’t without issues. Metal, wood and asphalt expand and contract at different rates, causing separation and loosening of the components. Nails that were once tightly set into the wood decking begin to work their way out. Metal flashings begin to get wavy (oil-canning), separating the bond of the shingles and causing abrasions. Even the shingles themselves are expanding and contracting, which can cause them to buckle if not properly spaced.

Temperature plays a large roll in decomposition. The components on your roof are going through stress on a molecular level. Over time, it catches up to them. Many of these issues are curbed by proper installation techniques that allow this slow movement to occur with the least amount of resistance.

The most important day in the life of your roof is the day it is installed. While you cannot avoid the season, you can avoid bad contractors. Be sure the installers of your roof have been trained by the manufacturer to follow their specific guidelines. Our installers at Arrington Roofing are highly trained and dedicated to building quality systems that last. We also have super warranties backed by GAF, the largest shingle manufacturer in the world, that only a handful of contractors can offer.

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