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The critical aspects are good detailing (particularly where different trades meet), careful product selection at the design stage and good quality assurance during construction.

n Poured concrete, plastered walls, plasterboard and well-jointed autoclaved aerated concrete blocks do not leak significantly.

n Careful selection of modern double-glazed weather stripped windows should pose little problem but gaps under and around window boards should be sealed.

n External doors, letter boxes and loft hatches should be specified with adequate seals.

n Services penetrations, flues and ventilation openings need to be detailed, preferably with collars.

Finally make sure your staff know about how to test dwellings and start testing some of your dwellings now, to see what is working and what is not before you find you cannot release the houses on your development because of a hold-up by the building control officer.

Andrew Eastwell, chief executive, BSRIA