** UBS downgrades French building materials maker Saint Gobain SGOB.PA to "sell" from "neutral", citing growing earnings risk from a weak U.S. roofing market and fading valuation support
** The brokerage flags earnings for its key Americas unit are 14% below consensus, seeing lower US residential roofing demand and sharp drop in industry utilization
** A historical valuation buffer has vanished, as the discount to its Sum-of-the-Parts (SOTP) value, has shrunk to under 10% from 40%-60%, UBS notes
** The broker adds that portfolio management through M&A is unlikely to offset its calculated negative organic earnings growth over the past two years
** Shares down 3.4% at 1134 GMT
** Out of 22 analysts that cover Saint Gobain, 17 rate it "strong buy" or "buy," and five rate "hold" - data compiled by LSEG
(Reporting by Hugo Lhomedet)
((hugo.lhomedet@thomsonreuters.com))