Wythenshawe Bus Garage Manchester

MANCHESTER BUS GARAGE - Early in 1939 work was begun on the Wythenshawe Bus Garage in the expectation of finishing it before the end of the year. But 1939 was a year of delayed expectations and this huge reinforced concrete building was not structurally complete until the latter part of 1941. The Ministry of Aircraft Production at once took it over and A. V. Roe & Co. Ltd. used it in the making of Lancaster aircraft, for which the enormous clear span made it especially suitable. It is now serving the purpose for which the City of Manchester Transport Department intended it - a depot for the Corporation bus services to the Wythenshawe Housing Estate, and it has room for 100 double-decker buses.

At the time it was built, it embodied some features of design which were new to Manchester. The most notable of these is the "Chisarc" roof. It has a clear span of 168 feet, with arched roofing-slabs only 2.75 inches thick, and there are no ties, braces, or inside column supports. Consequently, every foot of floor-space can be used.

SAVING IN MATERIALS - Shell-roof construction is based on the natural laws which give strength to the shell of an egg, the “stressed skin” being the structural element. The application of these laws to a building of this sort amounts, very briefly, to an extension to three dimensions of the two-dimensional methods used in arch design. By arch construction the depth that would be needed at mid span for a girder is greatly reduced. In shell construction the thickness of concrete needed for a slab design is greatly reduced by the thrust or tensions in the curved surface, which are in turn carried by the stiffening beams at the edges. This not only saves material but means that there is less weight to be carried, with considerable resulting economies. In the main garage a single barrel-vault, 2.27 inches thick, with a radius of 160 feet, spans between two hinged arches at 42-feet centres, which also resist wind and temperature stresses. These hinges are just below ground-level and rest on lead plates.

The washing-room forms a wing at right angles to the main building. It is roofed with four barrel-vaults, each of them 16 feet in radius and 16 feet 6 in. wide. They span a distance of 58 feet between the continuous beam end-frames. In the repair hall, which is separated from the main garage by expansion joints, the roof has seven vaults, each of a radius of 22 feet 6 inches and a width of 33 feet They give a clear span of 132 feet The end-frames are 232 feet long and expansion joints are provided to allow for movement due to changes of temperature. There are special roof-lights throughout. These methods have provided nearly two acres of unobstructed floor-space in the three sections of the building, and are an impressive example of the merits of this type of reinforced concrete construction with its very low maintenance costs.

SAVING IN LABOUR - Labour-saving was the keynote in planning the layout of the building. Incoming buses first pass through washing-bays with high-level platforms and are cleaned from the tops downwards. Ladders are not needed. There are sumps for extracting oil and grease from the waste water and sludge before it goes into the drains. The buses then go through the testing-shops before entering the main garage. Among the usual devices for bus maintenance there is a new one for keeping radiators hot during off-duty hours. Flexible pipes which connect to adaptors on the radiators send a constant flow of steam through the cooling-system of each bus so that the water is kept at a temperature which makes for easy starting. This not only gets the buses off the mark quickly but prolongs the life of the engines by doing away with the hard wear of starting a cold engine every day. Another innovation is the arrangement of the inspection-pits, which are lined with glazed tiles and have lighting which shows up the engine and chassis without dazzling the mechanics at work.

The garage is heated by the "Plenum" system and there is a low-level extractor for removing the heavier-than-air fumes which come from the engine exhausts. And there are staff dining-rooms, social and rest rooms, a milk bar and administrative offices. The building was designed by the City Architect, Mr G. Noel Hill, FRIBA, MTPI;  and J. A. King & Company were the contractors. Chisarc and Shell “D” Limited prepared the reinforced concrete design for the "Chisarc" roof; their consulting engineer was Mr H. G. Cousins, B.Sc., MICE.

Reference    Concrete Quarterly No. 1, July 1947, pages. 44-47.