Gaumont began his professional career in 1994 in the Castorama team.
In 1997, the two majority shareholders of Réno-Dépôt Inc., the Michaud family and Molson Companies Limited, sold their interest in the company to the French group Castorama S.A. In 1998, the British group Kingfisher PLC acquired a large block of shares from the Castorama S.A. group to become the majority shareholder.
According to a press release of October 10, 2013, AG Real Estate France will develop a 113,000 m2 logistics platform for Castorama on a site in Saint-Martin-de-Crau.
Also in 2005, Ellen MacArthur set a new world record for a single-handed non-stop circumnavigation in the trimaran B&Q/Castorama.
He ran Gitane-Campagnolo, Renault-Elf-Gitane, Système U-Gitane, Super U, Castorama, and Cofidis; riders under his direction included Van Impe, Hinault, Laurent Fignon, Greg LeMond, Charly Mottet and Marc Madiot.