Former Working Mast House Building Number 26

This is a former working mast house, now a store, located within the Sheerness Dockyard on Great Basin Road. Constructed between 1821 and 1826, it was designed by Edward Holl, the architect for the Navy Board, and engineered by John Rennie Snr. The building is built of yellow stock brick with a slate hipped roof, and features an internal iron frame.

Architecturally, it is a rectangular, open-plan structure with a 14-window range by 10-window range. The north and east fronts have a ground-floor arcade of round arches, originally with rubbed brick heads and iron fanlights, although many have been altered or replaced. The first-floor windows have rubbed brick flat heads. Large hoist doors are present on the north side, and the east elevation has 12-pane metal tilting casements. The south front has ground-floor round-arched openings recessed within the wall, now blocked at the ends. The obscured east elevation features wide flat-headed openings with cast-iron lintels dated 1825, some containing double doors with small-paned lights above. A plat band, cornice, and parapet complete the exterior.

The interior contains a ground-floor cast-iron column frame with diagonal cruciform struts supporting longitudinal beams with parabolic bottom flanges. Lateral beams are bolted along the sides, all with curved top profiles, and sockets hold joists supporting timber boards. The upper floor mirrors this design, with columns and braces bolted to valley beams. A five-bay roof is constructed of cast-iron ties and struts, with king and princess rods; the two central bays feature glazed ridges, and the central area of the first floor has been opened, likely in the 20th century. A rear stair leads down to an iron-gated culvert, formerly connecting to a mast pond.

Historically, the mast house was one of a pair used for constructing and storing masts and small boats, flanking a central mast pond which has since been demolished and filled in. Built above a mast tunnel culvert leading to underground vaults for submerged mast storage, the vaults are also now filled in. The iron frame is significant as an early 19th-century development of metal and fire-proof structural systems, conceived by Holl and utilized in the Devonport Ropery (1815), Chatham Lead Mills (1818), and Archway House, Sheerness (1825). A similar system was used in the 1813 New Tobacco Warehouse in London. This building represents one of the last surviving dock buildings from Rennie’s planned dockyard and is a rare example of a once-common naval building type.