The next five years will feature the biggest housing construction boom in Sydney's history, according to forecasts released by the state government.

The forecasts predict almost 185,000 new houses and apartments will be added to the city by 2021 – about 85 per cent more properties than were built in the previous five years.

Parramatta will be home to the largest increase in dwellings, with another 21,450 properties added to the council area, according to the forecasts by the Department of Planning and the Environment.

The next largest increases are in the City of Sydney council area, with 18,250 new dwellings; Blacktown, with 13,600 new properties; and Canterbury-Bankstown, with 12,200 new dwellings.