Building Ventilation
Building Ventilation
(Asphalt Shingles, Cedar Shakes & Shingles)
General
Eave protection is used to protect the eave and valley areas of steep sloped roofs from ice dam damage. An ice dam usually forms when the interior heat of the building warms the snow on the roof, causing it to melt and run down to the eaves. Normally, the eaves are overhanging the building and not heated from the inside. This allows the water to freeze and form an ice dam. As the ice dam grows bigger, it forms a barrier, which prevents water from draining. The water backs up behind the dam and gradually forces its way under the shingles (or shakes, tiles, etc.), through the roof deck, and into the structure. The results can range from minor staining to severe water damage to the structural members.
Eave protection is designed to prevent the water from reaching the deck and leaking into the structure. Recently a number of companies have developed self-adhesive, rubberized asphalt composite sheet materials. Properly formulated and installed, these sheets have the potential to provide a longer life and better performance. The slope and climate conditions are considerations for selection, please see Section 7.
Underlayment is used in the field areas (where eave protection is not required) of the roof to provide a secondary protection beneath the shingles during weather events that force water back up the slope underneath the shingles. Nail Applied materials qualify only as underlayment on roof slopes of more than 1:3 (4/12).