Some companies offer to install new shingles or other roofing materials over the top of existing materials on your roof. This practice is often called a “roof overlay” or a “layover” and is problematic for several reasons. Without tearing off the existing material, there is no way to provide a complete inspection of the roof deck itself. Potentially hiding or even creating underlying issues. Also, should your roof ever develop a leak, tracking with multiple layers is much more complex and may result in failed repair attempts. It's also challenging to address ventilation issues without removing the old roof. Beyond that, flashings and accessories have a limited life expectancy, and an overlay typically does not include replacing accessories or flashings. The roofing material will also have a shorter lifespan because of several factors, including additional environmental stress.
Other adverse outcomes caused by overlays are negative home value and a less attractive installation. In most areas, including the Pacific Northwest, a layover can detract from the value of your home, completely negating any “savings” you may have noted with the upfront cost. These are just a few reasons why Valentine Roofing always performs a complete tear-off and replacement of every roof we install!