A complete pre-fabricated package for an AIROH house consisted of 2,000 components that were assembled in four sections and delivered to the intended site by truck. The fully equipped bungalow weighed about 10 tons and provided 675sq ft of living space, including a fully equipped kitchen and bath. In 1947 an AIROH home cost £1,610 (equivalent to $6,488 at $4.03 US dollars to the pound in1947) each to produce, not including the cost of the land and installation. A total of 54,500 AIROH homes were eventually constructed in the UK.
AIROH Aluminium Bungalow
The Aluminium Bungalow was the most highly prefabricated house in the Temporary Housing Programme.
Production of complete bungalows was concentrated in five large factories, well distributed over the country, and assembly lines were used to produce each house in four fully finished units, which required mechanical handling and transportation on modified mobile trailers. This eliminated the need for centres for distribution centres dealing with individual components. In early 1944, ministers and industrialists believed that if a temporary house in which the principal parts were aluminium alloy, could be successfully prefabricated in former aircraft factories, then much of the labour employed there during the war, could be retained and gradually re-absorbed. Further to this, stocks of alloy, including aircraft scrap, could be used to help solve the national housing issue.
The intention was to proceed with the prefabrication of 50,000 steel houses, along with alternative types, because some 200,000 fabricated steel kitchen bathroom units and sets of steel cupboards had already been ordered (partly due to the cancelled Portal Bungalows). When it became clear that steel houses could not be produced in sufficient quantity before the middle of 1946, it was decided to concentrate instead on the temporary aluminium house, as this had an earlier projected delivery date. The development of the design for the aluminium bungalow was entrusted to a joint organisation of the Aircraft Industries and the Ministry of Aircraft.
Aircraft Industries Research Organisation House (AIROH).
The Post-War government insisted that the AIROH ‘house’ was to be designed and created specifically for the Temporary Housing Programme, with a projected lifespan of at least 10 years. The designation, ‘temporary,’ was not very palatable to the designers, but the condition was accepted.
The original intention was that practically all the temporary houses of whatever type should be fitted with the prefabricated steel kitchen-bathroom and cupboard sets, designed by the Ministry of Works. However, owing to supply and production difficulties, only 28,500 Kitchen Bathroom sets, and 27,000 cupboard sets had been manufactured by January 1948. Nevertheless, a large proportion of both Arcon and Aluminium houses were eventually fitted with them. The cost of these sets, and especially the refrigerators, which were added to the equipment, far exceeded the original costing estimates.
In the aluminium bungalow, the entire plumbing system was contained in one of the four units, so that no plumbing joints had to be made on site.
Road transportation of the units was also subject to a number of restrictions in relation to weight and size, but the lightness of the metal and air-entrained cement grout that was used to fill the external wall panels, enabled the heaviest unit of two tons, 15 ¼ cwt (that containing the kitchen and bathroom assembly) to be kept within the maximum transportable load. The 7ft 6 in. limit width on many roads had to be acknowledged and accepted as a fundamental design consideration.
The image below shows the plan of the bungalow with the plumbing assembly separating the bathroom and kitchen, at the living-room end, of which is housed an openable slow burning stove with a back boiler.
The Ministry of Supply’s specification for the bulk of alloy material to be used with alloy DTD 479, contained copper, manganese and magnesium, with the permissible additional up to 10% of pure aluminium for sheet and strip, and up to 40% for exclusions.
The sheet and strip used to the external cladding of the walls and roof of the bungalow was coated on both sites with 99% pure aluminium and was known as Alclad. Apart from the nailing down of the floorboards, which was done by hand, the entire production was mechanised. The wall frames, like shallow trays, were first sprayed on the inside with hot bitumen, then immediately passed beneath a battery of cement pourers and filled with air-entrained grout, which provided an insulating layer. The partly made wall panels then passed through low pressure steam drying ovens which enabled the grout to reach full strength in 48 hours, after which a further layer of hot bitumen was sprayed over the exposed cement face and whilst still hot, a ¼ in. plasterboard inner lining was pressed and secured by nails into wood fillets fixed to the frame.
The layers of bitumen were intended to provide a water and vapour barrier, and in addition, to take up any relative movement that might be caused by different rates of thermal expansion. Unfortunately, the bitumen did not provide the continuous vapour barrier expected, because the first layer of bitumen became unevenly displaced over the aluminium sheeting when the grout was poured. Additionally, the formation of small bubbles in the second layer also prevented continuity.
The finished wall was 2 1/4in thick, and gave a thermal insulation value, equal to that of a brick cavity wall of 11-ins with a plaster lining. The underside of the corrugated roof sheeting was likewise sprayed with bitumen, to which 1/16-in. millboard was fixed. The ceilings would have fibreboard on timber frames fixed to the aluminium trusses and included additional insulation of glass-fibre, under which was a layer of building-paper intended to act as a vapour barrier. The final assembly of the components was done on the conveyor-belt system, during which the final paint spraying was carried out. Previously, the aluminium parts requiring special paint treatment, such as windows, had passed through the appropriate process is of pickling, dipping and drying.
Each unit of the house emerged fully wired for electricity, glazed and painted.
One of the five factories concerned had four assembly belts installed, one for each unit of the bungalow; in another factory, the four units travelled along a single belt. It was possible for this system to bring one unit to completion every 12 minutes of the working day. Careful regulation of the production of component parts was vital to maintain an even flow. A shortage or surplus of materials could cause the production line to be halted, with crippling consequences.
The houses were contracted and produced under the direction of the Ministry of Aircraft Production (later, the Ministry of Supply). The position of the sites, concrete slabs and dwarf walls on which they were erected, was the concern of the Ministry of Works, whose responsibility ended when the houses were finally accepted by the local authority in whose area they were built.
When the four low trailers, each carrying a unit of the house, arrived at site, they were backed up between collapsible gantries which lifted the units onto trolleys fitted with screw-jacks and rollers, enabling the units to be pushed along parallel sets of rails to their allocated foundation slab. For erection on sloping sites, a 5 ton travelling crane used.
As soon as one unit was ready to be joined to the next, a wooden batten was placed in a vertical channel in the edge of the wall panel, ready to engage in the adjacent abutting wall panel. The batten acted like the tongue in matchboarding. The cavity in front of the battens was then packed with glass-fibre, which was finally enclosed with spring cover strips of aluminium; similar strips protected the roof joints.
At the Eves and base of the wall, units were locked by V-shaped interlocking connector blocks, of aluminium, through which a pin was driven horizontally. The main services were all carried in the kitchen-bathroom unit, and work on joining them up could begin even before the house was fully erected. Extension of electrical wiring to the remaining units was made by plugs and sockets. Erection time would vary a great deal depending on the site; 20 man-hours is commonly quoted.
The floor area of the aluminium bungalow was 629-sq.ft.
In a Government white paper of October 1945, the cost of each house was estimated to be £1365. By 1947 though, the cost had risen to £1610, and this did not include the factory tooling costs for the programme, a cost which could not possibly be realised over just 10 years of use. This is why the Aluminium Bungalow became, by far, the most expensive of all the temporary houses. A huge financial cost revelation that did much to discourage the sustained development of ‘temporary’ prefabricated building constructions.