Melbourne is the only Australian capital that allows medium density housing to be built on most of its residential land, according to a new study of zoning restrictions from a pro-housing collective.The Victorian capital, where housing is also more affordable than in the other five major capitals, is the clear outlier nearly four years on from a nationwide pledge to wind back planning restrictions to ease the housing crisis.A comprehensive "atlas" of Australian zoning laws, compiled by the "YIMBY" group and published for free online, tracks the development rules for every residential site in Australia's eight capital cities.A site is deemed "restricted" if it is capped at two storeys, heritage protected, zoned for detached housing only (preventing townhouses), or otherwise designated low density Hobart has constraints on 97 per cent of its land, Adelaide 92 per cent, Darwin 88 per cent, Perth 87 per cent, Brisbane 86 per cent, Sydney 81 per cent and Canberra 74 per cent."The fact that most of the residential land in our cities is locked up under highly restricted zoning makes sense of why we can't build the homes we need," co-author Jonathan O'Brien said.In a landmark housing agreement struck in 2022 and 2023, Australia's federal, state and territory governments signed onto the view prosecuted by leading economists that the dominant cause of the housing crisis was a lack of supply, held back by zoning laws.Governments agreed to a target of 1.2 million new homes over five years, starting in mid-2024 and made up of individual targets for each state and territory