Following the takeover, a new stationmaster's house was built at Sea Mills, at a cost of £240. The stationmaster is recorded as having kept a variety of farm animals and sold eggs to passengers. Increased levels of traffic saw the line through Sea Mills doubled in the early 1900s, and the opportunity was taken to rebuild the station. A second platform opened on 6 January 1907 to the west of the tracks to serve northbound trains. The original platform now exclusively served southbound trains, and was lengthened to , the same length as the new platform. A station building was constructed on the original platform in a domestic style, with an arched terracotta entrance, spar-covered walls and a high-pitched tiled roof. The building contained a booking hall, booking office, toilets and a ladies' waiting room. A smaller building on the northbound platform contained a general waiting room. The subway under the bridge over the River Trym was also built at this time, with the porter's job being expanded to include washing the rubbish out of the subway after high tide, for which the railway provided a hosepipe and Wellington boots. By 1910 there were 17 trains from Bristol to Avonmouth and 15 back, increasing to 21 and 19 respectively by 1920, though not all stopped at Sea Mills. The station was completely closed on Sundays.