Municipal building codes require that the first 36" of the roof deck be completely covered with underlay. The bottom of your roof will see the most run-off of water, since all precipitation to come into contact with your roof will flow down. This is typically the first area that shingle wear will present itself. For these reasons, the building code insures the
homeowner of a back up plan. By insuring that the bottom 36" are covered with an underlay, typically asphalt saturated felt, homeowners are given the opportunity to visually notice shingle wear prior to water penetrating the roof deck.
At Lakeshore Roofing & Eavestroughing, insuring the longevity of your shingle roof begins with the underlayment.
As seen in the photo, metal drip edging is attach to the bottom of the roof deck to insure that water run-off will find the eavestrough even when the bottom shingles begin to bend due to age. Next, we install 36" of ice & water shield. The ice & water shield is a self-adhesive membrane that seals to the metal drip edging to prevent moisture from backing up the roof under the shingles. The saturated felt does not seal to the roof deck, and can therefore allow water to pass underneath. Also, the ice & water shield has a finished backing similar to that of the shingles, providing a greater barrier against water run-off. At Lakeshore Roofing we still install the felt underlay on the roof deck. We simply install it above the ice & water shield. In total giving the roof deck up to 70" of underlay from the bottom of your roof. (34" higher than required by building codes)
