Asphalt shingles are the most popular residential roofing material on the market, and for good reason: They’re cost effective, adaptable to a wide variety of roof forms, and come in an array of styles and colors to suit almost everyone. But while most builders have spent their share of time nailing off shingles, there’s no shortage of unanswered questions on the subject. How do 20-year shingles differ from 25-year shingles? Why is felt underlayment required in fire-rated roof assemblies? What’s the most leakproof valley detail? To fill in some of the blanks, we put those questions and others to a half-dozen industry experts: Carl Cash, a former chair of the ASTM D- 08 committee on
