Paul Casseri, Product Manager, Atlas Roofing Shingles and Underlayment Division.
Self-adhering waterproof underlayment is an adhesive-backed membrane designed to provide a secondary layer of protection against leaks or damage caused by extreme weather. Properly installed, it can minimize moisture penetration into critical areas of the roof system, such as along the eaves, in rakes and valleys, and around roof penetrations such as flues, exhaust vents, chimneys and skylights.
But the adhesive properties that help peel-and-stick underlayment protect the roof deck also make it difficult to remove, especially if it has been in place for a long period of time.
The first step is to pull away any underlayment that can be easily removed, taking special care not to damage the roof deck in the process. With the underlayment out of the way, the deck can be more easily inspected for signs of deterioration or damage.
Removing the underlayment reduces the build-up of materials that could generate a leak-producing water stop. It also eliminates unevenness that could cause aesthetic issues in newly installed shingles.
When more than one layer of self-adhesive underlayment is present, all layers should be removed. If they can’t be removed easily, the contractor may be forced to replace affected areas of the decking.
However, if only one layer is present and it cannot be easily removed without causing damage to the deck, roofers can install a second layer of underlayment over the existing membrane.
When a second layer is applied, roofers should offset laps in the new and existing underlayment. The new layer should be “feathered in” by extending the new material a minimum of 8 inches beyond the edge of the existing material to reduce or eliminate chances of water stops and unsightly aesthetic issues.
Protecting the roof deck is paramount. If the self-adhering underlayment layer refuses to pull away from the deck easily, the contractor may be left with no choice but to remove and replace the deck itself. Failure to do so may cause bigger problems down the road.
As Product Manager of the Roofing Shingles and Underlayment Division, Paul Casseri is responsible for all areas of product management, including product initiation, feasibility, design, development and testing. He is a graduate of Penn State University and has more than 20 years’ experience in the building products industry. For more information on underlayment options, visit
www.atlasroofing.com/roof-underlayment/specialty.