Why do shingles need an underlayment between them and the roof deck?
A. The underlayment does three things for your shingle roof. 1) First the underlayment temporarily protects the roof from the rain and snow between the time the deck is installed and the shingles are applied. 2) Second, it offers the shingles some protection from any uneven or rough corners or edges that carpenters may have missed. 3) Finally, quality roll roofing products (such as those available from NBP) will have lines on paper, helping you to maintain a horizontal plane while installing shingles without the need of chalk lines.
