William Blair analyst Ryan Merkel views the 9% pullback in shares of Beacon Roofing Supply (BECN) over the past two weeks as overdone. After speaking to management, the analyst attributes the stock weakness to fears of new construction peaking. Only about 10% of Beacon's sales are tied to new construction, however, with 90% tied to replacement, Merkel tells investors in a research note. He notes the company's close peers, Watsco (WSO) and Pool Corp. (POOL), have sold off far less. Merkel adds that his firm's roofing surveys indicate that fundamentals remain healthy and there has been no noticeable slowdown. He sees a good buying opportunity at current levels and keeps an Outperform rating on Beacon.