Projections by the state government show Wollongong, Shellharbour and Kiama will need 28,900 new dwellings to keep up with population growth between 2011 and 2031, or 1445 extra homes a year.

When the Shoalhaven is included, projected demand is for 39,050 new dwellings.

Urban Development Institute of Australia NSW chief executive Stephen Albin said the figures "should ring alarm bells for our decision makers", and formed a case for planning reforms.

"Under the current system it will be impossible to reach this target because of a range of impediments to housing delivery including prohibitive red tape and excessive fees that too frequently make housing delivery unviable."

In Wollongong, where the projection is for 16,100 new dwellings, Lord Mayor Gordon Bradbery said he "thoroughly disagreed" the target was impossible.

He pointed to the West Dapto land release - aimed at making 19,000 lots available by 2050, and the Calderwood development as contributors.

"We're well aware of these projections and we're quite across the implications," he said.

"We're well on track to facilitating those lots out at West Dapto."

According to the Illawarra Urban Development Program, released by the state government in October 2013, the Illawarra produced 1125 new dwellings, on average, in each of the preceding 10 years.

Completed buildings ranged from a maximum of 1557 in 2002-03 to a minimum of 583 in 2009-10.