Sydney's housing boom is coming to an end as restrictions on loans to property investors and a raft of new property developments combine to depress prices, insurance giant QBE says.

After surging 56 per cent in the past four years, the median house price in Sydney will remain broadly flat in the next three years, QBE said in its annual housing outlook released on Thursday. Sydney apartment prices are seen falling 6.8 per cent by June 2019, as slowing growth in rents and unit prices damps investor appetite.

The unprecedented housing boom has been fuelled by the RBA's record-low interest rates, a growing population and a shortage of supply, locking young people seeking to buy homes out of the market. The big banks have tightened lending standards for property investors after pressure from regulators to avert a bubble, and some state governments have imposed stamp duty surcharges on overseas buyers.

In light of these developments, "prices are forecast to soften through the three years to 2019, which is likely to be positive for housing affordability," said Phil White, chief executive officer of QBE Lenders' Mortgage Insurance.