Common roof systems in Arizona:
The asphalt single
The manufacturing process
Asphalt shingles are manufactured by embedding a fiberglass mat in modified bitumen, then surfaced with a blend of colored mineral granules, both for protecting asphalt and providing a pleasing appearance.
3-tab shingles named for their appearance having 3 tabs are standard and perhaps one of the oldest styles of shingles.
Laminated shingles also known as architectural shingles, contained more than one layer laminated (glued) together to give a more 3-dimensional appearance. Laminate has become very popular with architects and builders for their appearance and easier installation.
Interlocking shingles come in various shapes and sizes. Installed in an interlocking method that provides superior wind resistance.
The system components
- The decking is typically a wood sheathing material. Technically, the decking is considered part of the "roof assembly." A solid deck is critical.
- Underlayment while never is seen, but it is nearly as important as the shingles. The underlayment protects the sheathing as well as providing a substrate for the shingles. Traditionally, asphalt-saturated felt is used; however, synthetic underlayment's have been more popular.
- Flashing provides additional waterproofing and is made of aluminum or galvanized steel. Flashings include edge flashing, penetration flashing, crickets, saddles and more.
- Vents, proper ventilation can make all the difference in the service life of any roof system. A complete roof system will always include properly designed ventilation. Unfortunately, ventilation tends to be neglected.
- Guttering and Downspouts
- The steep-sloped roof system is designed to shed water off the roof. The guttering and downspouts are designed to move the water away from the building to a more desirable location.
Service life expectancy
Every roofing system has a service life cycle. Starting with the installation, and ending with its removal and replacement at the end of its service life. Several factors will affect the actual service life of the roof system from proper to improper installation to excellent or poor maintenance.
- 3-tab shingles 15-18 years
- Laminated and interlocking shingles24-30 years
- Heavyweight designer shingles up to 50 years
What is an overlay and why you shouldn't do it
An overlay is when a roofer installed an additional layer of asphalt shingles over an existing layer. Over time the fasteners from the first layer will work their way through the top layer, leave small holes all over the roof. These holes allow water intrusion and subsequent damage, and when it comes time to re-roof the house, it will be a costly job. Much more expensive than just having the first roof system removed. I never recommend an overlay.
Roof Consultant and Roofing Industry Advocate