During the past several months, NRCA has received several reports of considerable building leaks when underlayment on a steep-slope roof system was left exposed as a temporary roof covering before installation of a finished steep-slope roof covering material, such as asphalt shingles or metal panels.
In light of these events, it seems a review of roofing industry guidelines for underlayment use as temporary weather protection is appropriate.
For steep-slope roof systems, underlayment serves several functions, including being a secondary weatherproofing barrier should moisture infiltrate the primary roof covering; meeting building code requirements and fire-rating classifications for roof assemblies; and complying with manufacturers' warranties. In some instances, underlayment also serves as temporary weather protection until a primary roof covering is installed. But for underlayment to perform adequately as temporary weather protection, it should shed water without allowing water to penetrate it.