Hydraulic Engine House (Building Number 38) South West of Number 9 Store with Bollard at South West Corner

The hydraulic engine house, built in 1861 by John Murray, Chief Engineer, is located southwest of Number 9 Store at HM Naval Base. It was extended around 1904. The building is constructed of red brick in English bond, with ashlar and gauged red brick dressings, and features a corrugated sheet roof.

This single-storey structure includes a two-storey accumulator tower at the west end, a northern boiler house, and a southern engine house extension. The exterior showcases a chamfered plinth, an ashlar impost band, and tall round-arched windows with metal glazing bars and radial heads set in gauged-brick round-arched recesses. The eaves feature a stepped dentilled band, cornice, and a flat-coped parapet that has been largely rebuilt.

On the southwest elevation, there are three bays on the left side from the 1904 extension, which include 16-pane sash windows, loading doors, and a pediment. The central accumulator tower has bays framed by pilasters and stepped bands, with a wider round-arched central bay that once served as an entrance, along with a first-floor band and cornice. The right bay has an inserted entrance. The southeast elevation has one bay recessed, while the northeast elevation features three bays with an early 20th-century entrance on the left and later sliding doors and windows on the right, beneath a rebuilt pediment. The northwest elevation is obscured by a later building.

A notable feature is a cast-iron inverted cannon bollard located approximately 3 meters southwest of the southwest corner. Inside the 1904 extension, there is a king post roof and robustly built corners, similar to those found in the Brass Foundry.

Historically, this hydraulic engine house was responsible for pressurizing the hydraulic system that operated eight cranes on Watering Island, nine capstans, and nine lifts, as well as the mechanism in the Chain Test House. It is recognized as a comparatively early example of a hydraulic engine house and holds group value with the Chain Testing House.