Synthetic Roofing Underlayments
These materials are tougher than felt, but do they perform as well?
A milestone in any construction project is drying in, usually defined as the day the roof sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. is covered with underlayment. Building codes require the installation of asphalt felt for several reasons: Underlayment keeps the sheathing dry until the roofing is installed, it provides some protection against leaks in case wind-driven rain gets past the roofing, and it provides a slight improvement in a roof’s fire resistance.
[To read more of Martin Holladay's article from the October/November 2011 issue of Fine Hombuilding, click the link below.]