Number 2 Ship Tank, Haslar Marine Technology Park (former Admiralty Experiment Works)

Number 2 Ship Tank is a covered model ship testing tank, workshop and offices constructed between 1927 and 1930 for the Admiralty. It stands within the Haslar Marine Technology Park, occupying a linear site aligned north-east to south-west parallel to Haslar Road.

The building comprises two principal components. At the south-west is a large square single-storey gabled workshop range containing facility areas, offices, store rooms and plant rooms. Attached to its north-east is an extremely long single-storey gabled ship tank range, creating a continuous 270-metre structure (extending to 283 metres inclusive of docks).

The building is constructed in red stock brick laid in English bond with red brick and concrete dressings, steel roof trusses and slate roof coverings.

The workshop range is designed in neo-Georgian style with a brick and concrete plinth and brick pilasters. Its south-east elevation forms the main entrance fronting Haslar Road, presenting a largely symmetrical composition of 21 bays. The central bay contains panelled doors approached by steps beneath a semi-circular moulded porch canopy carried on huge corbels, flanked by rusticated brick clasping buttresses, with a 1930 date stone and parapet above. Three bays to the left of the entrance and four bays to the right contain pairs of six-over-six sash windows with red brick voussoirs and concrete cills, separated by plain brick pilasters. Beyond these are gabled bays, each containing three sash windows beneath an oeil-de-boeuf window and rusticated brick clasping buttresses. At the south-west end an access ramp leads to a roller shutter for bringing models or machinery into the workshop. The range is lit from above by rows of skylights and two raised ridge lanterns.

The south-west elevation has a tripartite round-headed window at its centre flanked by two further round-headed windows and two small square-headed windows at the north-west end. The north-west elevation presents an irregular composition with a central gable and ten flanking bays of casement or fixed windows separated by plain brick pilasters. The central gable has three doorways and two windows to the ground floor and a four-light window to the attic. A lean-to extension with timber double doors lies immediately to the north-east, whilst immediately to the south-east is a single door raised above ground level with steps providing access, designed to accommodate a heating chamber below. Many of the doors and windows on this elevation appear to be late 20th-century replacements, some in uPVC.

The ship tank range extends 64 bays and features a concrete arcade of canted arches beneath the windows on each side, supporting walkways flanking the tank. Two earthen banks, likely spoil from the tank's excavation, obscure most of the arcades. The north-west and south-east walls have a large clerestory window to each bay, separated by plain brick pilasters. The windows contain 30 panes with a central pivoted opening. At the 28th bay from the north-east end are projecting brick winch openings on each side, raised on plinths beneath flat roofs, originally used for accessing the mid-point of the waterway, although infilled in the late 20th century with uPVC doors and panels. A two-storey gabled cross range to the south-east elevation at the 41st bay from the north-east end contains a plant room, with the slate roof featuring two rows of skylights and three raised ridge lanterns.

Internally, the workshop range originally housed a workshop, machinery control room, dining room, drawing and recording offices, fitting room, and battery and generator rooms for the towing carriage. The main entrance leads into a hallway and corridor with a terrazzo floor. Flanking the entrance are offices, store rooms, meeting rooms and staff rooms, largely with late 20th or early 21st-century fixtures and fittings, with many doors replaced and some modern false ceilings and partitions. Opposite the main entrance is a doorway into the workshop or facility area, a large concrete-floored space open to the roof, which is constructed of canted steel howe trusses. Steel I-beams attached to the roof structure support a travelling crane used for lifting models through timber double doors at the north-east end of the facility area into the ship dock beyond, including the Iris model. The north-west side contains further offices, plant rooms, store rooms and bathrooms.

The ship tank range contains three docks at the south-west end: a pair of shallow concrete docks flanking a much deeper central steel and concrete dock designed to facilitate the launching of models into the tank's waterway. The concrete tank within the main range is 12 metres wide and 5.4 metres deep with gently tapered sides. It is 270 metres long but extends to 283 metres inclusive of its docks. Two narrow walkways run along the length of the tank. The waterway walls support steel traveller rails carrying the models and recording equipment mounted on a substantial trussed wheeled carriage, which was replaced in 1983. This includes the Planar Motion Mechanism, which measures the forces acting on a model at various attitudes or when oscillated in a vertical plane. The bays are numbered and the distance in metres from the wavemaker is marked at intervals along the waterway. The towing carriage interfaces with various towing rigs. A wavemaker was installed at the north-east end in 1995, whilst beaches were installed at the south-west end at the same time. Behind the current modern wavemaker is the original wavemaking equipment. The waterway is open to the steel roof, which is supported by canted howe trusses of 16-metre span, seated on RSJ stanchions set within the brick pilasters of the side walls.

Modern elements including modern steel railings, buffers, overhead bus bars, light fixtures, cabling and piping throughout much of the range, along with the wheeled carriage replaced in 1983, the Planar Motion Mechanism, towing rigs, wavemaker and beaches, are excluded from the listing under section 1(5A) of the Planning (Listed Buildings and Conservation Areas) Act 1990 as not being of special architectural or historic interest. However, any works to these features which have the potential to affect the character of the listed building may still require Listed Building Consent.