Number 6 Boathouse (Building Number 1/23) And Slipway To Front

NUMBER 6 BOATHOUSE AND SLIPWAY, HM NAVAL BASE

This boathouse, originally a mast house, was built in 1845 to designs by Captain RS Beatson RE, with Mr Rigby as contractor. The building was bomb-damaged in 1941 but remains substantially intact except at the east end, which is now a shell with first-floor windows blocked and the second floor missing.

The structure is constructed of yellow brick in ashlar bond with ashlar dressings and an internal cast-iron frame. It has three storeys, with the ground level on the west side being lower to provide access to the adjacent mast pond. The plan is five-sided, formed by a rectangular base with a diagonal wall built across the south-east corner. The roof, a replacement from the mid-to-late 20th century, is of corrugated iron with roof lights.

The exterior features an ashlar plinth on the west elevation, a band over the ground floor, and eaves band and cornice. Windows throughout have flat brick arches, projecting ashlar sills, and replacement metal windows that are proportionally shorter on the ground and second floors. Loading doors are distinguished by eared ashlar architraves with tripartite keystones.

The west elevation contains nine bays, with the three central bays breaking forward. At the centre of each three-bay section is a large round-arched entrance with imposts, keystones, studded double board doors, fanlights, and a lamp to the left of the central door. Iron mooring rings are set at low level. A tapering brick chimney, corniced and rising behind the parapet, stands at the right-hand corner.

The north elevation has fifteen bays with two-bay end breaks and a three-bay central break featuring central loading doors on each floor, now blocked. The east elevation contains six bays with loading doors on each floor of bays 2 and 5. The south-east elevation has five bays with central loading doors. The south-west elevation comprises eleven bays with a three-bay central break containing central loading doors; the first-floor door is equipped with a crane. A double board door to the ground floor serves bay 3.

Internally, the structure employs cast-iron columns and cast-iron segmental-arched beams across shorter spans, with cast-iron trussed beams spanning wider spaces. On the third floor, braced riveted steel roof trusses support the structure. Wooden floors run throughout. The ground floor contains three slipways separated by a double row of columns (fourteen columns per row). Above the central slipway the ceiling is open, designed to allow mast-fitting. At the west end, a trap door is strengthened by extra columns.

The stone-sett slipway slopes down to the Mast Pond along the front, fitted with iron mooring rings. Tracks of granite slabs with iron rollers lead up to each entrance of the boathouse; the track serving the right-hand entrance is now built over.

Beatson designed this building to carry an exceptionally heavy load and it represents a significant early example of large-scale, sophisticated load-bearing iron-framed construction. It is of particular interest alongside his other work at Portsmouth—the Fire Station and Chain Testing Shop. This building represents one of the last uses of trussed beams before the 1847 Dee Bridge disaster enquiry discredited their use. It contrasts with the traditional timber construction of the 1844 Lower Boat House at Chatham and the innovative 1859 Boat Store at Sheerness designed by GT Greene. The interior arrangement permitted boats to be lifted internally through to the upper floors.