An eave protection membrane is a thin underlay beneath shingle, shake and tile roofs that prevents water from leaking into the home. It runs along the edges of a roof closest to eaves, valleys, ridges and flashings. On all new roofing structures in Ontario, eave protection is required by law.
There are various types of eave protection membranes; however, the chief differences deal with installation. Regarding composition, most membranes use modified asphalt and/or fibre glass, but some products now include glass into that mix.
In the winter, eave protection is what keeps the roof from damage should ice damming occur—build up from runoff water that solidifies in the eaves. Of course, the membrane itself cannot stop ice damming from happening, as the issue results from other roofing and environmental conditions to do with temperature.
Over time, underlays can deteriorate and thus need regular inspection. When exposed directly to water and sunlight, the membrane can even disintegrate—a reason why it’s imperative to fix loose or missing shingles quickly. A comprised eave protection membrane can cause internal leakage as well as rafter and soffit rotting.