A milestone in any construction project is drying in, usually defined as the day the roof sheathing 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.]
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