Rattenbury worked for the Canadian Pacific Railway as their Western Division Architect. His best known work for the CPR was a Chateau-style hotel, The Empress, which was built in 1904–1908 in Victoria, with two wings added in 1909–1914. The architect, however, fell out with the CPR and then joined their competition, the Grand Trunk Pacific Railway. He designed many hotels and stations for the GTP, but they were never completed because of the death of the president, Charles Melville Hays, in the sinking of the RMS "Titanic" and the company's subsequent bankruptcy. The CPR allowed him to return, however, and he built the second CPR Steamship Terminal in Victoria in 1923–1924 in association with another architect, Percy James. Rattenbury and James also collaborated in the design of the Crystal Garden at the same time although they later had a public conflict over Rattenbury's refusal to give James credit and payment for his work on the Garden.