New housing costs at Wigram south of Christchurch rose 16 per cent in one year, which Sewell blamed mainly on material cost rises.
Labourers on the sites had received no pay rises, so he asked how material prices could have escalated so fast.
Dr David Whittaker, technical director at Beca in Christchurch, and Dr Lindsay Jones, a New Zealander who is chief executive of the San Francisco and Christchurch based seismic building business Maxlide, talked about construction techniques in earthquake-prone areas.
Jones said the uptake of seismic isolation systems - including those using the lead rubber bearing systems - was "frankly disappointing". People recognised the increased safety offered by buildings which had these systems yet the uptake had been slow, he said.
Residential projects with these systems commanded a 10 per cent premium yet it only cost an extra 2 to 5 per cent to develop new buildings with these systems, Jones told the delegates.