Valleys and penetrations through the roof decking are some of the areas of the roof most vulnerable to leaks. A peel-and-stick bituminous membrane is installed for protection at these critical locations, including all roof valleys, roof-to-wall transitions, and roof edges to minimize ice dam damage in cold climates. Metal or plastic flashing is usually installed along with the membrane at wall intersections. Flashing is also installed around chimneys, vent stacks, and any other roof penetrations. Some builders install peel-and-stick membrane or a paint-on damp-proofing over the whole roof.