...Fitch Ratings has affirmed France-based building materials group Compagnie de Saint-Gobain's (Saint-Gobain) Long-Term Issuer Default Rating (IDR) and senior unsecured rating at 'BBB'. The Outlook on the Long-Term IDR is Stable. Fitch has simultaneously affirmed Saint-Gobain's Short-Term IDR at 'F2'. The affirmation reflects Saint-Gobain's strong business profile as one of the largest and most diversified building products companies globally and its improving operational performance in recovering end-markets in Europe and the US. We expect financial headroom to be limited if the group proceeds with the acquisition of Sika AG. In this case Fitch would forecast FFO adjusted net leverage to fall towards 3.5x, our guidance for the ratings, within one year of completion....