Number 3 Slip Cover

Number 3 Slip Cover is a covered slip built in 1838, likely designed by Sir Robert Seppings of the Royal Navy and constructed under Captain Brandreth of the Admiralty Works Department. It features a timber frame, weatherboarding, and a corrugated sheet roof.

The building has a U-shaped, single-depth plan and is a single storey with a 10-bay range. The weather-boarded walls include wide, low small-paned windows in each bay, with four taller windows located to the left of the open eastern end. The roof is very large and mansard-shaped, consisting of two tiers of continuous roof lights, curving around the eastern end with shallow hips and three tiers of roof lights in each section.

Inside, there is a massive timber frame made up of square section timber aisle posts with iron bases and knees, diagonal braces, and cantilevered principal rafters that extend to overhang the aisles, along with braced collars.

Historically, timber roofs began to be constructed over dry docks in navy yards around 1814 due to the rapid deterioration of timber ships exposed to the weather during construction. The trusses are supported by the cantilever effect of the overhang beyond the posts. At the time of its construction, these were the widest roof spans in the country, and this slip cover is the largest of the three surviving examples, with the others located at Devonport. It reflects the increase in the size of warships permitted by Seppings's redesign of ships' bracing. Number 3 is the oldest slip cover at Chatham, as the one from 1813 was destroyed by fire in 1966, and it is part of a notable group that includes metal-framed covers built between 1845 and 1857 to the north.