Green Belt designation does not prohibit every building project. For an application, the first policy question is whether the development falls within a category that is not inappropriate. If it does not, a demanding very-special-circumstances test applies.
This guide covers England and uses the National Planning Policy Framework published on 17 August 2026, particularly policies GB6–GB8 and Annex A. Older articles using paragraphs 154 or 155 should be checked against this replacement Framework.
Confirm the designation and the planning route
Find the site on the adopted policies map. Green Belt is a planning designation, not a description of how green the land looks. A landscaped residential plot, an industrial site and a field can all raise different questions within the same designation.
Check permitted development separately. The additional householder restrictions associated with article 2(3) land do not arise from Green Belt status alone. The actual class, property history, planning conditions and any Article 4 direction still matter. The General Permitted Development Order sets those legal rights; the Framework sets planning policy.
For an application, identify the relevant local plan and national policies, including other constraints such as flood risk, heritage and ecology. Clearing the Green Belt policy test does not decide every other issue.
Extensions and replacement buildings
Under GB7(1)(b), the relevant existing building must be lawful, permanent and substantial. Extensions or alterations must avoid a disproportionate increase over the original building. A replacement should retain the same use and must not be materially larger than the building it replaces.
The original-building comparison looks to 1 July 1948, or the building as first constructed if later. Prepare an accurate development history rather than comparing only with the house as you bought it. A previous owner's extension can therefore matter to your proposal. These tests and the definition are in policy GB7 and footnote 40.
There is no universal percentage in that national policy which guarantees an acceptable extension. Prepare existing, original and proposed floor areas, volumes, heights and plans as appropriate, and explain the relationship between them. A single calculation can conceal a much greater change in height or massing.
Other categories and grey belt
GB7 includes qualifying agricultural development, limited village infilling, certain affordable housing, redevelopment of previously developed land and specified other uses, each subject to its wording. The category must fit the whole proposal.
Grey belt is a defined policy category within Green Belt: previously developed or other land that does not strongly contribute to checking large built-up areas’ sprawl, preventing neighbouring towns merging, or preserving historic towns’ setting and special character. Those are purposes (a), (b) and (d) in GB2. GB7(1)(g) requires more than a site being labelled grey belt: it also addresses remaining Green Belt purposes, evidenced unmet need, sustainable location and, for qualifying major housing development, the Golden Rules. The August Framework also contains a station-related residential or mixed-use category at GB7(1)(h), with accessibility, physical relationship, infrastructure and other requirements. Read the complete GB7 criteria and Annex B definitions.
Do not treat nearby railway tracks, an untidy site or some hardstanding as proof of a policy route. A useful feasibility assessment sets out the precise category relied upon, the evidence for each requirement and any requirement that is not yet met.
What are the Golden Rules?
The Golden Rules in GB8 concern specified major housing development within, or on land released from, the Green Belt. They address affordable housing, necessary infrastructure and accessible green space. Their detailed requirements, exceptions and viability provisions need to be read for the particular site.
They are not a general requirement that an ordinary householder extension must provide affordable housing. Equally, describing a major housing scheme as redevelopment does not answer whether GB8 applies.
For a development site, make the relevant contributions part of the initial feasibility work. Leave room in the layout and financial appraisal for infrastructure and green space before treating a notional unit count as deliverable.
When are very special circumstances needed?
GB6 applies the very-special-circumstances test to inappropriate development. The case must clearly outweigh both the Green Belt harm and other harm, with substantial weight given to Green Belt harm, including openness. This is a demanding planning balance, not a standard form exemption.
Keep this separate from exceptional circumstances for changing Green Belt boundaries through plan-making. An application does not redraw the designation boundary merely because the applicant would prefer the site to be outside it.
Worked example: extending an already enlarged house
Suppose a cottage was originally small, acquired two extensions and is now proposed to receive another wing. Comparing the wing only with today's enlarged cottage may give an incomplete picture.
The evidence file should reconstruct the original building, document the lawful additions and show the cumulative proposal. The design team can then test whether a smaller extension, altered roof form or reuse of existing space better addresses the applicable policy. None of those options guarantees approval, but they give the assessment a factual basis.
Use current policy with the local evidence
Annex A makes the August Framework relevant to decisions from publication and explains the treatment of inconsistent development-plan policies. Do not discard every older local policy simply because a new Framework exists. Read our NPPF guide for the wider position.
Sources and review
The August 2026 Framework's Green Belt chapter, glossary and implementation provisions, and the linked Order, were compared on 8 September 2026 with automated research assistance. This source check is not professional approval of a proposal. Green Belt classification, measurements and the planning balance require site-specific evidence.