§ Mr. Rookerasked the Secretary of State for the Environment what is the significance of the limitation given in his Department's circular 28/84 to the eligibility of owners of prefabricated reinforced concrete houses designed before 1960; and whether dwellings designed after 1960 are not expected to be liable to cracking and concrete spalling to a significant extent as a result of corrosion of the embedded steel reinforcement.
§ Mr. GowThere are two distinct types of prefabricated concrete dwellings in this country. Those designed before the wars and immediately after the last war were designed to provide, in the main, two-storey houses and to be assembled by hand. That meant that the prefabricated sections had to be very light and slender. Because they are slender there is little protection for the steel reinforcement and the Building Research Establishment has found that all prefabricated reinforced concrete houses built before 1960 are likely to be affected by the processes of carbonation and attack of chlorides which will lead to corrosion of the reinforcement and consequent cracking of the concrete.
Prefabricated reinforced concrete dwellings designed after 1960 were generally made by casting whole walls and 215W floors as single components. These are massive and robust and were used to build not only houses but flats up to 20 or more storeys high. Because of differences in design and improvements in the quality of reinforced concrete, the steel reinforcement in these components is better protected. There is no evidence that the main load-bearing components of these buildings generally are liable to the rapid deterioration and consequent cracking and spalling found in prefabricated reinforced concrete houses of the previous generation.
§ Mr. Rookerasked the Secretary of State for the Environment if he will assess the extent to which all buildings designed after 1960 and using reinforced concrete structures are likely to be affected by the processes of carbonation and attack by chlorides.
§ Mr. GowThe study of the effect of carbonation and attack by chlorides on reinforced concrete structures generally has been a main part of the Building Research Establishment's research programme since 1975. The general principles have been established and published in 1982 in BRE digests 263, 264 and 265, copies of which are in the Library. The processes are complex and the way in which a particular building or class of buildings may be affected is not easily established without testing. It is for individual owners to inspect their buildings as necessary but, as I announced on 23 October last at columns 554–55, the Building Research Establishment is now giving special and urgent attention to the study of large panel system dwellings designed after 1960, which will include investigation of the effect of carbonation and attack by chlorides.