TQ 76 NE CHATHAM MAIN ROAD (West side) Chatham Dockyard 762-1/8/76 No.3 SLip Cover GV I Covered slip. 1838, probably to designs of Sir Robert Seppings, RN; constructed under Captain Brandreth RE of the Admiralty Works Department. Timber frame, weatherboarding and corrugated sheet roof. PLAN: U-shaped aisled single-depth plan. EXTERIOR: single storey; 10-bay range. Weather-boarded walls with wide, low small-paned windows to each bay, 4 taller windows to the left of the open E end. A very large mansard-shaped roof has 2 tiers of continuous roof lights, and is curved round the E end with shallow hips and 3 tiers of roof lights to each section. INTERIOR: a massive timber frame of square section timber aisle posts with iron bases and knees, diagonal braces, to cantilevered principal rafters that extend out to overhang the aisles, and braced collars. HISTORY: timber roofs were being built over the dry docks in navy yards from c1814, because of the rapid rate of deterioration of timber ships exposed during construction to the weather. The trusses are supported by the cantilever effect of the overhang beyond the posts. At the time they were the widest roof spans in the country, and this is the largest of the three surviving examples, (the others are at Devonport), reflecting the increase in the size of warships allowed by Seppings's re-design of ships' bracing. No.3 is the oldest slip cover at Chatham since that of 1813 was burned down in 1966, and one of a remarkable group with the metal-framed covers of 1845-57 to the N (qqv}. (Sources: Coad J: Historic Architecture of Chatham Dockyard 1700-1850: London: 1982: 181 ; Coad J: The Royal Dockyards 1690-1850: Aldershot: 1989: 114-116; The Buildings of England: Newman J: West Kent and the Weald: London: 1976: 206; The Newcomen Society: Sutherland RJM: Shipbuilding and the Long-Span Roof: Paper read at Science Museum: 1989: 9). Listing NGR: TQ7590369410