Brownfield land, made buildable.

The same paragraph asks decision makers to support the development of under-used land and buildings, and it names the kinds of place it means: space above shops, service yards, car parks, lock-ups and railway infrastructure. The weight settles nothing else. Flood risk, ecology, heritage, access, design and viability all stay live, and a site that fails one of them fails on that ground rather than on its brownfield status. Where the land is also protected for employment use, the release test is a different question again, set out in the guide to loss of employment land.

The duty comes from the Town and Country Planning (Brownfield Land Register) Regulations 2017, which required registers to be published by the end of that year. Part 1 holds every site the authority has assessed as suitable for residential development, whether or not it already carries permission. Part 2 is a subset of Part 1: the sites the authority has decided should carry permission in principle. The usual threshold for entry is a site of at least a quarter of a hectare, or one capable of taking at least five dwellings, though smaller sites can be entered. Absence from a register proves nothing: entry is the authority's decision and coverage is patchy.

It arrives by one of two routes, on application or by the authority entering a site in Part 2 of its brownfield land register. On application it is decided in five weeks and lasts three years by default; through a register it lasts five. Technical details consent then follows, with ten weeks for major development and five for anything else. The route is deliberately narrow. It is closed altogether to development needing environmental impact assessment, to habitats development, to householder work and to minerals, and the application route is closed to major development, which means ten homes or more, a thousand square metres or more of floor space, or a site of a hectare or more. On heavily constrained land the principle cannot really be separated from the detail, which is why a full or outline application stays the realistic route.

A separate regime sits behind that one. Part IIA of the Environmental Protection Act 1990 lets a local authority identify land as contaminated where significant harm or significant pollution of controlled waters is being caused, or where there is a significant possibility of either. Liability falls first on whoever caused or knowingly permitted the substances to be there, and where no such person can be found it can reach the current owner or occupier. Planning does not run that regime, but it sets a floor against it. The working standard is suitability for the intended use, so the same ground can need one thing for housing and another for a warehouse. What to ask for before the money moves is set out in the guide to buying land.

The statutory objective is at least a ten per cent increase in biodiversity value, and a biodiversity gain plan has to be approved before development may lawfully begin; the authority has eight weeks to approve or refuse one unless a longer period is agreed. Exemptions changed on 6 August 2026: a site of 0.2 hectares or less inside the red line is now exempt, but that exemption falls away if priority habitat on the site would be harmed. Open mosaic habitat on previously developed land is itself a priority habitat, and it is exactly what a long-vacant yard or siding grows. So the small-site exemption is least reliable on the sites that look emptiest. There is more in the net gain guide.

The other triggers are critical drainage problems identified by the Environment Agency, land a strategic flood risk assessment puts at increased future risk, and land at risk from other sources where a more vulnerable use would be introduced. The sequential test is a separate question, and it applies however developed the land already is. It asks whether reasonably available sites exist at lower flood risk within an area of search the authority defines. Where they do, permission can be refused on that ground, and where the sequential and exception tests are applied and not met, development should not be allowed. Neither being previously developed nor a housing shortfall exempts a site: guidance is explicit that the absence of a five-year housing land supply is not a relevant consideration in applying the test to an individual application, though housing can still weigh in the wider balance. Why a site fails in principle is covered in the guide to why development sites fail.

The mechanism is a credit equivalent to the existing gross floorspace of the vacant building, set against the floorspace of the new development. Guidance gives the arithmetic: a building of eight thousand square metres demolished as part of a ten thousand square metre scheme leaves a contribution of a fifth of what would otherwise be sought. It does not apply to a building that has been abandoned, and abandonment turns on the condition of the property, how long it stood unused, whether anything happened there in between, and what the owner intended. Authorities also look at whether a building was emptied in order to claim the credit. On the right conversion this is worth more than any move a designer can make.