Walls And Gates Of The Boat Basin, Docks Number 4 5 And Slipway

The Boat Basin, dry dock numbers 4 and 5, and slipway form part of the Sheerness Dockyard, dating to approximately 1814 and designed by John Rennie Snr for the Navy Board. Alterations occurred in the early 20th century. The complex comprises a square wet basin with parallel docks and a slipway along the east side, a dry dock to the south, a graving dock in the middle, and a building slip to the north.

The dry dock (No.4) has stepped sides in two sections, two slides on each side, and a curved head. It retains Rennie's original curved iron inner gates and an iron outer caisson. The graving dock (No.5) features a wide, flat floor with steep, 20th-century concrete sides and ends, extended in its design, and an iron caisson constructed in 1866 by Easton and Anderson. The slipway has a sloping stone floor with low, stepped sides and rails for a boat carriage. Approximately 60 cast-iron mooring bollards are present, each inscribed with "John Sturges & Co, Bowling Ironworks, Near Bradford, Yorkshire."

Historically, the dockyard represented a notable feat of marine engineering, with masonry built on piles. Dry dock No.4 is of a type pioneered by Rennie at Chatham No.3 dry dock around 1821, and was the first dry dock to incorporate iron gates, making it a uniquely complete example of early 19th-century dock technology. Sheerness Dockyard, unlike other royal dockyards, was entirely rebuilt at once, and represents the last operative dock remaining from Rennie's original layout. The complex forms a group with the later Boat Store and Buildings 84 and 86, all within Rennie’s model of an early 19th-century dockyard.