TQ 9074 GREAT BASIN ROAD Sheerness Dockyard 93/6/10004 Former working mast house, Building Number 26 II* Mast and boat house, now store. 1821-26, by Edward Holl, architect for the Navy Board, and John Rennie Snr, engineer. Yellow stock brick with slate hipped roof and internal iron frame. Rectangular open plan. EXTERIOR: 2-storey; 14x10-window range. North and east fronts have a ground-floor arcade of round arches with rubbed brick heads and iron fanlights, most altered or replaced, and rubbed brick flat heads to first-floor windows, larger hoist doors to the N side, 8112-pane metal tilting casement to the E; S front has ground-floor round-arched openings within recesses, blocked to the ends. E elevation obscured by later building, has wide flat-headed openings with large cast-iron lintels dated 1825, some containing double doors with small-paned lights above. Plat band, cornice and parapet. INTERIOR: contains an internal frame of ground-floor cast-iron columns with diagonal cruciform struts supporting longitudinal beams with parabolic bottom flanges, with lateral beams bolted along the sides, all with curved top profiles, with sockets in the sides holding joists, supporting timber boards. Upper floor has similar columns and braces bolted to valley beams, with 5-bay roof with trusses of cast-iron ties and struts with king and princess rods; 2 central bays have glazed ridges and the central area of first floor opened, all probably C20. A stair in the rear leads down to the culvert with iron gates formerly leading to the mast pond. HISTORY: one of two matching buildings used for constructing and storing masts and small boats, either side of a central mast pond, the second store and the pond now demolished and filled in. Built above a mast tunnel culvert leading from the river to underground vaults for storing masts under water, the latter also apparently filled in. The frame is part of an important strain in the early C19 development of metal and fire-proof structural systems, devised by Holl and used at the Devonport Ropery (1815), Chatham Lead Mills (1818) and subsequently Archway House, Sheerness (1825). The 1813 New Tobacco Warehouse, London (II*), used a similar system of diagonal cast-iron braces though to a timber roof. One of the last surviving dock buildings from Rennie's planned dockyard, and one of only two examples of a once-common naval building type. (Sources: Rennie Sir J: The Formation and Construction of British and Foreign Harbours: London: 1851:41; Sheerness, The Dockyard, Defences and Blue Town: 1995: NMR BI NO 93279). Listing NGR: TQ9087474922