Lack of finance and weak demand are behind the delays for approved residential construction projects proceeding to commencement, a survey says.

The Housing Industry of Australia says about half of its 1300 members had approved residential projects sitting on their books that had 'not been started or completed'.

This represented about 34,000 new homes, the nation's peak residential construction group said on Tuesday.

A lack of construction finance was behind 44% of all apartments not proceeding to commencement, the survey said. The figure was 33% for townhouses, duplex and villas, and 32 per cent for detached housing.

More than half of those surveyed said a lack of sales was the reason behind approved townhouses, duplex, villas and detached houses not starting.

The Age