Building 55, former Officers' Mess, Catterick Garrison

Building 55, the former Officers' Mess at Catterick Garrison, was designed in 1915 by Major Bertie Harold Oliver Armstrong RE (1873-1950) and renovated and extended around 1924. It is constructed with a steel girder frame and concrete walls clad in orange-brown bricks laid in stretcher bond, with painted galvanised steel windows, asphalt and felted gable roofs, and brick chimneystacks.

The building follows an H-plan as a single-storey structure, comprising a pair of parallel nine-bay Armstrong huts linked by an offset corridor. The main range has two projecting end wings, and small storerooms were added to the rear around 1924. Small modern brick-built store extensions and timber verandahs to the rear are excluded from the listing.

The main north-east elevation comprises a central five-bay range with a canted entrance porch in the left-hand bay, lit by four narrow three-light casements. Each bay has a low-set ventilation brick, with the junction of each bay marked by a square concrete pad projecting from the wall surface, forming the base for the steel frame's wall posts. Each bay is lit by a 20-light painted galvanised steel window set in a timber frame, with a moulded brick sill and concrete lintel. The two projecting gabled wings are lit by pairs of similar casements; the eastern wing has a four-bay side elevation with four windows, whilst the western wing is blind with a modern fire escape door. The rear elevation has two closely set 20-light windows and a door in the southern gable, flanked by three similar windows.

The corridor link connecting the ranges is pierced by two modern galvanised and two narrow water closet windows on its west wall, and two modern frosted three-light galvanised windows on its east wall. The gable of the east wing is lit by two 20-light casements.

The rear range, formerly the service range, has a similar appearance on its northern elevation facing into an open courtyard. A doorway with a concrete lintel is situated at its western end, flanked to the left by five casement windows and two to the east of the corridor link. The west gable has a pair of water closet windows and the east gable has two windows. The south-west elevation has two former single-storey service ranges projecting from it: the eastern range formerly housed the kitchen, storeroom, and pantry with an attached lean-to boiler room accessed by an external door from the courtyard and featuring a blocked coaling hatch in its rear wall. The western range, with an L-plan, formerly contained the beer and wine storerooms with an attached coal store; the rear of both ranges has patched brickwork.

The central three-bay length of the rear wall of the rear range faces into a courtyard between the two service ranges, protected by a modern timber-framed verandah clad in corrugated plastic sheeting. The western end of the rear wall has a three-bay elevation with a central doorway beneath a narrow rectangular fanlight and a sixteen-light casement window to either side on concrete sills, protected by another modern timber-framed verandah. All roof surfaces are clad in felt and drained by cast-iron and plastic rainwater goods. Five brick chimneystacks with terracotta pots rise from the main range roof and two from the rear range, along with a cement flue from the boiler room.

Internally, surviving chimneybreasts remain in several rooms. The entrance porch leads into a hallway spanning the width of the main range, with moulded concrete skirting, plain painted walls, and a fibre board-clad roof soffit. An exposed steel roof truss stands against the west wall. A doorway in the hallway's east wall leads into the former mess room in the east wing, latterly occupied by the British Forces Broadcasting Services; 1920s brick fireplaces and chimneybreasts have been removed from this space and replaced with a modern soundproofed partition. A door in the west wall leads into an axial corridor spanning the length of the rear of the main range. An open doorway at the southern end of the hallway gives access to the link corridor, which has toilets on one side and a small kitchen on the other. The axial corridor has a pair of doors in its north wall, one accessing the former ante room and the other a former card room. The western end of the corridor turns 90 degrees north to give access to an office and the former billiard room in the west wing.

The link corridor leads into the rear range via a large family welfare room, originally subdivided into a central axial corridor flanked by a bar, wash-up, and pantry, with a rear door to the courtyard. The windows in the north wall are barred, the roof is underdrawn, and the tie-beams are encased. A modern double door in the west wall leads into a smaller welfare room aligned across the building's axis, formerly occupied by the waiters' day room, plate store, and beer store. An exposed rolled-steel I-beam wall post bearing the maker's mark of Dorman Long stands within this room. A doorway in the west wall leads into the former mess servant's accommodation area, now converted into offices. The eastern room of the rear range, formerly the kitchen with associated stores and pantry, is accessed externally from the rear courtyard, as is the boiler room.