Duxford: Building 84 (Hangar 3)

Aircraft hangar, one of a group of three, built in 1917-18 to War Office Directorate of Fortifications and Works Drawing Number 332/17. It was designed by Lieutenant-Colonel BHO Armstrong of the Royal Engineers. A signals neon beacon platform was added at the west end in 1931. The annexes were altered and extended in 1928 and 1935.

The hangar has brick buttresses, curtain walls and internal piers, all painted, with timber roof trusses covered in profiled steel sheeting. The annex roofs are of corrugated steel sheeting.

The building forms the westernmost of three identical contemporary hangars standing in-line on a north-east to south-west axis on the north side of the airfield. It comprises paired sheds, each of 100 feet span and 25 feet clear height, with full-height and full-width sliding/folding doors at the east and west ends. The 15-bay north and south sides, running 170 feet overall, have brick buttresses spaced at 11 feet 4 inches intervals supporting 'Belfast' roof trusses. Lean-to annexes adjoin the north and south sides.

The east and west openings have 'Esavian' sliding/folding doors with diagonal timber boarding running to an overhead track, with a deep apron above running the full width of the hangar to compact brick pylons at each end. Wicket doors within the 'Esavian' doors provide personnel access. At the central valley to the west end, a steel access ladder rises to a signals neon beacon platform erected in 1931, supported by four reinforced brick piers and comprising a reinforced concrete platform with simple pipe handrails.

The north and south walls have raking buttresses carried to the eaves soffit, with half-brick curtain walls between. Each end bay is plain while the remaining 13 bays have a full-width steel casement window in 27 panes set as a high clerestory; alternate bays also incorporate a six-pane pivoted opening section. Above these windows is a deep apron band. The pylons at each end into which the doors slide are square shafts.

The roofs are in profiled steel in flat segmental form, with continuous ridged patent glazing roof lights to the central 13 bays and a line of patent glazing either side of the central valley. The eaves have a plain painted fascia with a gutter. Above the horizontal apron to the door track is a flat segmental pediment to each shed, with close-set vertical joint divisions to metal cladding and a wide central ventilation louvre.

Single-storey lean-to annexes flank the north and south sides, modified in 1928 and 1935. Bays three and four of the southern annexe, running the full length of the hangar, were built in 1928 to accommodate the pilots' rest room. This section is deeper than the remaining 13 bays and has three steel casement windows of two lights in eight panes. The 11-bay range adjoining it contains double entrance doors plus five steel casement windows in 16-panes, each incorporating a four-pane pivoted opening section, all covered with security grilles, along with a two-light steel casement with small-pane glazing. At the west end are three wooden doors and four single-light windows with top-opening lights.

The north side has a 13-bay annexe with a nine-pane steel casement window to the former paint shop at the westernmost end. Bays two to four, added in 1928 to accommodate officers for a Squadron Leader, the Adjutant and clerks, are deeper than the rest of the annexe, with three two-light casements with small-pane glazing. A small gap giving access to a doorway with late 20th-century double doors in the fourth bay separates the 1928 range from the remaining 11 bays of the annexe. This section is largely comprised of steel casement windows in 16-panes, each incorporating a four-pane pivoted opening section.

The paired sheds have a central row of brick oblong piers with narrow central openings to arched heads. On each side is a moulded stone corbel carrying the roof strutting. Running between the piers to support the gutter and provide stiffening is a series of 'diaphragm' walls, one brick thick, on flat segmental arches.

Each bay is divided by wooden-latticed 'Belfast' roof trusses spanning from the central row of piers to the buttresses in the outer walls. The trusses, all whitewashed, have a flat bottom chord and a bowed upper profile formed in a series of straight members. All truss members are small-section softwood, with doubled main members sandwiching a close-spaced diagonal grid infill. At the end supports, the trusses are strutted to shaped stone corbels, and this 'knee' area is strengthened by diagonal close-boarded sheeting. Longitudinally there are 5 sets of simple cross bracing and diagonal sheathing on small purlins carried to the roofing. In the end bays there is extra horizontal bracing to the bottom chord.

Walls are painted and the floor is of concrete.

Late 20th-century interventions include an entrance lobby in the north-east corner, while most doors giving access to the annexe bays are also late 20th-century replacements.