Nearly half of Brisbane land zoned for townhouses and apartments is too small to support those developments, new research from Griffith University has found.
The findings raise questions about whether the city can meet its ambitious housing targets.
Dr Rachel Gallagher from the Department of Tourism and Marketing analysed Brisbane's zoning alongside land parcel data to determine how many properties could realistically take advantage of these planning changes.
"Brisbane lots are typically 400 square meters in size, but at least 600 square metres is required to accommodate multiple dwellings," Dr Gallagher said.
"Only 51.2 per cent of land zoned for multiple dwellings actually met the minimum size requirement for this kind of development.
"To take advantage of the planning policy, landowners would need to combine their lots, a process known as land assembly, something that was difficult, slow and relatively uncommon."
Upzoning was intended to increase housing supply by encouraging infill development in existing suburbs, but the findings suggested much of the planned capacity may not be deliverable in practice.
The Queensland Government's South East Queensland Regional Plan required Brisbane to deliver more than 210,000 new homes by 2046, with nearly 90 per cent planned as higher-density housing in existing suburbs, making the success of infill development critical.
Earlier research by Dr Gallagher showed higher-density development occurred where it was feasible, typically on larger sites, in areas historically planned for increased density, and with access to appropriate infrastructure.
The new study found many upzoned areas did not meet these conditions, raising questions about whether current planning approaches could realistically deliver the housing they promised.
While minimum lot sizes presented a primary constraint, local factors such as character protections, vehicle access and parking could further influence whether redevelopment was feasible in Brisbane's established suburbs.
"In low-demand locations, upzoning may never translate into increased housing supply but risked inflating land values, while low-density zones constrained development in many desirable suburbs where demand for more dwellings was high," Dr Gallagher said.
"Policymakers need to engage more critically with what exists on the ground, because the physical characteristics of land, like its size, ultimately determine whether planning decisions can deliver the expected outcome."
The paper 'Misaligned Policy and Practice: Does Upzoning's Implicit Reliance on Land Assembly Undermine Densification Goals?' was published in Urban Policy and Research.
