History:
Before the Royal navy set up its first general hospitals in the 18th century, sick and wounded seamen were looked after by contracted staff on hospital ships, in hired houses and inns at the principle ports and in reserved beds at the main London hospitals.
In wartime this was more difficult and the idea for a dedicated hospital evolved. Permanent hospitals for the sick and wounded had been established abroad: in Jamaica in 1704, Lisbon in 1706, Minorca in 1711 and Gibraltar in 1746. The 'Commission for the sick and hurt' authorised the construction of hospitals at Gosport, Plymouth and Chatham in 1744.

The principles set out for the plans for the Haslar Hospital, near Gosport, were that it should be a 'strong, durable and plain building' and for consideration to be given to ' the disposition, situation and dimensions of the wards for sick men, the convenience of light and air; to avoid narrowness as also crowding beds too close together.'
Ref Richardson Hariett (Ed) (1998)p 79

The hospital catered for a full range of illnesses and included wards for medical, surgical, fever, flux, smallpox, consumptive, scorbutic and recovery as well as lunatics. In the late 19th and early 20th centuries, Haslar was one of the most important naval hospitals in the country. It became the main lunatic asylum for the navy as well as providing for infectious diseases between 1898-1902.

Architecture:
The building was designed by Theodore Jacobsen and built between 1746-61.

It is a massive red brick building with Portland stone dressings, comprising double blocks of wards arranged around three sides of a quadrangle. The double blocks, possibly influenced by the Queen Anne Block at Greenwich, are separated by a narrow courtyard. The administration block consisted of the main entrance, council room, dispensary and offices. The east and west blocks contained large wards placed end to end and with access from one to another. Nurses rooms, officers apartments, wcs and staircases were arranged around central light wells.
Building was devoid of ornamentation, in accordance with admiralty instructions apart from a carving by Thomas Pearce on the pediment over the administration block.

Haslar was the biggest hospital and the largest brick building in England when it was built. The courtyard was never completed although railings were erected along the south side to deter desertion.