The 5M steel framed house is constructed from a lightweight
composite steel-and-timber-framed system which was designed by the Ministry of
Housing and Local Government Research and Development Group, otherwise referred
to as M.O.H.L.G.
The 5M was
essentially a progression of the earlier CLASP system of construction that had
been used in the erection of school buildings during the 1950s.
The first 5M dwelling was constructed in 1961 and general
production followed in1963. The 'M' in the title 5M represents the term
'module', This form of construction utilized the 1ft 8 inch or five times the
module of 4-inch grid system. Imperial measurement still dominated at this
time; however, 4 inches was very close to the metric scale of 100mm. By
comparison, a 12M (4'0") system related to the standard Imperial sheet
material size of 8'0" x 4'0".
The long-term concept of the Modular House, was to design
and build using interchangeable components of standard sizing that would be
compatible with other manufacturers systems who deployed the same size modular
The 5M system used a number of standard sized components
which were utilized to produce a wide variety of plans and layouts. Unfortunately,
the system was not a great success as it was considered to be grossly over
designed and susceptible to water penetration by many outspoken critics. The
excessive number of joints and cladding fixture points dramatically increased
the risk of water ingress.
Some Critics even went so far as to suggest that the
internal steel frame was surplus to requirement as the modular steel
construction alone, offered sufficient support,
Approximately 3500 5M bungalows, two and three storey houses
and low-rise flats were constructed between 1963 & 1970.
The basic design is of single- or two- or three-storey flat-roofed terraced dwellings with a distinctive continuous fascia at first-floor level and at roof level.
The ground-floor elevations are largely storey-height door and window units, with intermediate panels clad with V-jointed vertical tongued and grooved boarding or exposed aggregate precast concrete panels.
The flank-end wall is clad with similar concrete panels or with brickwork.
At first-floor level a wide flat plywood or asbestos cement fascia panel encircles the terraced block.
The upper-floor elevations are clad with a variety of forms of decorative tile hanging. A matching fascia panel encircles the terraced block at roof level and distinctive vertical timber cover strips mask the joints at corners.
The roof is flat with an up stand around the perimeter. The rain-water is drained down internally.
The range of possible designs is wide. Some of the terraces are very long, up to twelve dwellings, and a combination of features such as single-storey extensions, link rooms over external passageways and steps and staggers are used to break up the line.
The single-storey extensions form enclosed porches, entrance hall storage areas or integral garages.
Many of these dwellings have recently undergone refurbishment work where the exterior walls have been Externally insulated with brick slip cladding or render application to the exterior. A brickwork outer leaf and the incorporation of pitched roofs (As seen below) have significantly altered the appearance of some properties making them difficult to identify in the future.
These points listed above do not constitute a comprehensive list of all possible defects.
Not all defects will necessarily be present in one property.
The list serves to highlight possible areas which should be subjected to close examination.
If significant corrosion of the steelwork has occurred, the extent of deterioration may be masked by the corrosion product itself. In such cases it is difficult to determine the condition of the steelwork solely by a visual inspection.
This limits the effective application of visual inspection techniques, including optical probes. If corrosion is observed, the affected component should be exposed in order to establish the full extent of deterioration and subsequent removal or repair.
Some of the 5M houses subjected to survey were in their original condition.
Steel stanchions were generally found to be in good condition. Deterioration of protective coatings and superficial corrosion is evident at the stanchion bases. Corrosion is occurring to the reinforcement in the kerb upstand and cladding panels largely due to carbonation of the concrete.
Rain penetration through cracks in the asphalt roof covering has led to wet rot in the plywood box perimeter beams.
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