The Building Regulations Advisory Committee reported in 2002 (after the Part L Robust Details, but during the production stage of the Part E details) that overlaps between the two should be explored to see how they might be merged.The conflict being that acoustic separation is often successful due to the mass of a structure, and thermal insulation relies generally on lightweight insulation.
However, the latest interim report on Robust Details by the government's Industry Advisory Group (IAG) states 'there is an anomaly in that the Part E details appear to deal better with issues of airtightness than do the Part L details themselves'.
Furthermore, it recognises that the Part E Robust Details are overdesigned (they have 'performance in excess of the regulation requirements even in the worst case tested'and 'there is little doubt the use of the Part E robust details will add some cost to construction over and above that for basic Part E compliance with post-completion testing).This? is in the order of a 10 per cent increase?'The IAG recommends that the overspecification of the details be reinterpreted as the underspecification of the regulations.
Thus we have a situation in which the new regulations, introduced only a year ago with the promise of reinforcing details has resulted in the late details superseding the regulations.Effectively, in some places, the Part E drawings are not even harmonised with the Part E text, let alone the Part L documentation.