Bison Wall Frame Buildings (Hansard, 25 July 1984)

§ Mr. Gow

The Department's letter of 5 October 1983 referred to the possibility that in Bison wall frame houses and flats failures could occur which, in exceptional circumstances, could present a safety risk, where:

(a) no effective mechanical connection is made between load bearing wall and floor panels, and/or the bearing of floor and bedding of wall panels is inadequate, and/ or the load bearing walls are not effectively restrained by buttress walls or spandrel panels;
(b) parapets are not effectively tied back;
(c) ties between the inner and outer leaves of external wall panels are lacking altogether, are insufficient in number per panel, or are of suitable material;
(d) inadequate cover or the presence of chloride has led to corrosion of the reinforcement and consequent spalling of pieces of concrete, in particular from external wall panels;
(e) pieces of exposed aggregate, used as a wall finish, are not adequately secured.

Forty-four of the 48 local authorities in England believed to own Bison wall frame houses and flats have replied.

The Department has written to each of the four remaining authorities to ask for a reply as a matter of urgency.

All 44 authorities which have replied have taken or propose to take some steps to ensure that their Bison buildings do not present a safety risk. Two authorities have concluded that, since their buildings are variants of the design and are of only one or two storeys, no action is needed. The remaining authorities have undertaken or are undertaking appraisals as follows:

Nature of fault	Number of authorities which have appraised or are appraising buildings
Connections between wall and floor panels and restraint of load-bearing walls (a)	27
Parapet fixing (b)	15
Ties between inner and outer leaves of external cladding panels (c)	11
Spalling concrete and loose aggregate finishes (d) and (e)	30

Nine authorities have examined their buildings for all the possible faults listed in the Department's letter and are undertaking remedial works as necessary. Seven authorities have decided that the buildings should be demolished, sometimes because they were suffering from faults, such as water penetration, which do not present a direct safety risk. But, frequently, the appraisals undertaken or in hand do not appear to address, or to address adequately, all the possible faults listed in the Department's letter. It may be that in the circumstances of the individual case more extensive appraisal is not necessary but the Department is writing today to all authorities owning Bison houses and flats to remind them that they should give further consideration to the need for investigations. The Scottish Office and the Welsh Office are taking similar action, on the basis of the replies received to the letters which they sent on 5 October 1983. The Department of the Environment for Northern Ireland will be getting in touch with the Northern Ireland Housing Executive following its letter to that body of 5 October 1983.

The replies to the letter of 5 October 1983 confirm that some Bison wall frame buildings can suffer from one or more of the defects listed in the letter of 5 October but the replies do not identify risks to safety other than those listed in the letter. The replies confirm that a particular type of fault can be present in some buildings, and not in others, of this design. The requirement continues to be for detailed appraisal of each building and, in view of the information and knowledge already available and of the advice which I have received, I do not consider that detailed general investigation by the Department of the Bison wall frame system is necessary.

The Department, and the Scottish Office and the Welsh Office, will continue to assist individual authorities by providing information on the nature of the faults which 727W have been identified and the remedial action taken by other authorities in so far as those authorities are willing for such information to be passed to others. The Department of the Environment for Northern Ireland will be taking similar action. The Building Research Establishment's advisory service is willing to advise local authorities and to assist them with any specific problems which they may have with Bison wall frame houses and flats.

Where there is a requirement for spending on remedial works to Bison wall frame dwellings, it is taken into account, in deciding the housing investment programme allocation of the local authority concerned, through the local discretionary element. Since the incidence, combination and scale of problems varies from building to building, and some buildings are reported to be free of them altogether, my intention is that this requirement for expenditure should continue to be taken into account through the local discretionary element, though I am ready to consider any representations which the local authority associations wish to make about it.