Self-adhered underlayments are being used with felt to protect all types of roofs.

Originally developed to protect against ice damming (a phenomenon caused mainly by poor roof insulation in northern climates), self-adhesive underlayments and substrates are becoming popular as industry experts and contractors embrace self-stick products for all kinds of roofs.

Adhesive membranes have several advantages over other types of flashing, according to Reinhard Schneider, technical development manager for Georgia-Pacific roofing products. Because they don't need to be nailed or screwed, there's less destruction of the roof deck and there are no holes to allow moisture to seep in. Plus, they don't corrode like metal flashing.

Peel and Stick As with all types of underlayments, peel-and-stick products are installed between the roof deck and the roof covering. They are designed to help the roof shed water and provide secondary weather protection for the entire surface area.

As a practical matter, peel-and-stick underlayment products get a building watertight in no time, allowing other contractors to start working on the interior without waiting for the entire roof to be complete, comments John Madden, of James Myers, a Beltsville, Md., roofing company.

Self-stick underlayments can be applied in certain full-roof applications, notes Tom Bollnow, senior technical director of the National Roofing Contractors Association (NRCA). For instance, they can be used over the entirety of a low-slope roof, which, he says, is more susceptible to water accumulation than are other designs.

Dynamic Duo Most of the time, however, peel-and-stick products are used in conjunction with traditional roofing felts (which are nailed across the entire roof deck), at roof penetrations, and on rakes, eaves, and valleys. Mixing self-adhesive membranes with traditional underlayments is less expensive than using strictly self-adhesive materials; roofing underlayment costs account for about 10% to 15% of any overall roofing budget, but pros estimate that peel-and-stick products may be three to five times more expensive than felts. —Stephanie Herzfeld is associate editor of REMODELING 's sister publication BUILDING PRODUCTS . A version of this article originally appeared in that magazine.