The roundhouse with its central turntable enabled service and repair of multiple steam locomotives under one roof. The original 250-foot-diameter facility, constructed in 1855 of Savannah Grey brick, consisted of forty stalls around a small, 50-foot hand-operated turntable. The building was partly demolished and enlarged with reinforced concrete construction in 1926, destroying its circular form to accommodate larger locomotives in thirty-four stalls. Only a segment of the original building, comprising seven stalls, survives west of the turntable. This section of the old roundhouse was dedicated to repair operations and includes an operational electric drop table for removing wheel assemblies. The central turntable was enlarged several times, culminating with the current functioning 90-foot motorized table installed in 1946 (restored in 2004).
Unless an engine was shut down for major repairs, it was necessary to keep steam locomotive boilers alive, which required continuous stoking and service, and the original roundhouse included water faucets in each stall for filling the tenders. In the expanded section, smoke hoods (or jacks) above each stall vented smoke from locomotives while the large, triple-hung sash windows provided light and ventilation, with additional ventilation from the monitor roof above. Each stall of the enlarged section was also provided with compressed air for pneumatic tools, acetylene for torches, and electrical outlets. The floors are surfaced with end-grain wood blocks treated with creosote which absorbed oil, providing a nonslip surface that yielded more readily to cast-iron tools when dropped. Pits beneath the tracks provided maintenance access to locomotives from below. All interior walls were originally painted white to enhance light levels.