Openness of the Green Belt and how it is assessed
Screening a building behind planting deals with visual impact and does nothing for openness. How inspectors assess spatial and visual openness, and what to measure.
Green belt openness is the absence of development, not the absence of harm to a view. That distinction decides plenty of appeals, because an applicant who has screened a building behind a hedge has dealt with visual impact and has done nothing at all about openness. The National Planning Policy Framework, in the edition published on 17 August 2026, keeps openness and permanence as the essential characteristics of Green Belts, and every assessment of a Green Belt proposal has to grapple with the first of them directly.
What follows is how inspectors and officers actually approach it.
What openness means in policy
Openness is a policy concept rather than a defined statutory term. The Framework does not give it a formula, and the courts have declined to invent one. In practice it means the extent to which land is free of built development, judged as a matter of planning judgement on the facts of the site.
The five purposes of including land in the Green Belt sit alongside openness rather than defining it. A building can harm openness while doing nothing to encourage sprawl or merge two towns. It can also serve a purpose poorly while leaving openness largely intact. Officers who collapse the two exercises into one produce reports that fall apart on appeal.
Read the Green Belt chapter of the current Framework before relying on any of this, because the chapter was restructured in December 2024 and again in August 2026, and the numbering people quote from memory is usually out of date.
The spatial and the visual
The leading authorities settle the shape of the assessment. In Turner v Secretary of State for Communities and Local Government, the Court of Appeal held in 2016 that openness has a visual dimension as well as a spatial one. In Samuel Smith Old Brewery (Tadcaster) v North Yorkshire County Council, the Supreme Court confirmed in 2020 that openness is not purely visual, that visual effect is capable of being a relevant consideration, and that whether to take it into account is a matter of planning judgement rather than a mandatory step.
So a proper assessment covers both. Spatially, how much built form is being added, how much land is being taken out of an undeveloped state, and how that compares with what is there now. Visually, how the development is perceived from public vantage points, and whether it reads as an encroachment into open land.
The two can point in opposite directions. A single-storey building set into a fold in the ground may have a real spatial effect and almost no visual one. Assessments that report only the flattering half of that are the ones that get taken apart.
Openness is not visual amenity
This is the mistake that recurs most often in householder and rural applications. Landscape character, visual amenity and the setting of a designated landscape are separate considerations with their own policy tests. Openness is about development, not about beauty.
Screening illustrates it. Planting a belt of trees around a new building reduces visibility. It does not restore openness, because the land is still occupied by a building, and it arguably reduces openness further because the planting itself encloses land that was previously open. Inspectors say so regularly.
The reverse also holds. A proposal can be visually attractive, well designed, and still cause substantial harm to openness. Design quality is not a defence.
Measuring volume, footprint and spread
Where the exception being relied on is a limited extension or alteration, or a replacement building, the Framework asks whether additions are disproportionate over and above the size of the original building, or whether a replacement is materially larger. Both invite measurement.
The workable approach is to present three figures side by side, for the original building, the existing building and the proposal.
| Measure | What it captures | Why it matters |
|---|---|---|
| Footprint in m² | Ground coverage | The land physically taken out of open use |
| Volume in m³ | Built mass above ground | Height increases that footprint alone hides |
| Spread and curtilage | How far development extends across the plot | Encroachment into land previously undeveloped |
Original building means the building as it stood on 1 July 1948 or as first built, not as it stands now after two previous extensions. Getting that baseline wrong is the single most common technical error in Green Belt householder work, and it usually favours the applicant, which is why officers check it.
Do not forget the things that are not the building. Hardstanding, parking areas, walls, gates, lighting columns, oil tanks and domestic paraphernalia all occupy land and all feature in appeal decisions on openness.
Duration and permanence
Openness has a time dimension. A temporary structure, a permission limited to a defined period, or a use that will cease and be restored affects openness differently from a permanent building.
Mineral extraction is the classic example: land is disturbed, then restored. Inspectors have accepted that the temporary nature of an operation reduces the weight of harm to openness, though it does not remove it. Where a temporary permission is being offered as mitigation, the restoration obligation needs to be secured properly, normally by a planning obligation rather than by hopeful wording in a condition. The same deliverability thinking runs through the fallback position and the real prospect test.
How the harm is weighed
Inappropriate development in the Green Belt is by definition harmful, and substantial weight is given to any harm to the Green Belt. Harm to openness is a separate strand from the definitional harm, and it should be identified and weighed on its own rather than folded in.
The balancing exercise then asks whether other considerations clearly outweigh that harm, so as to amount to very special circumstances. Very special circumstances need not be rare, but they must be more than the ordinary benefits any development brings. Housing need, agricultural need, and personal circumstances all feature, with varying success.
The December 2024 Framework introduced the grey belt concept, which identifies Green Belt land that contributes less strongly to certain Green Belt purposes. It changes the route into the policy rather than the openness assessment itself, and the definition has moved between editions, so check the current wording rather than a summary written when it was first announced. Rural sites released this way still need the same evidence base, much as an affordable housing scheme on a rural exception site does.
Where assessments go wrong
Five failures account for most of them. Using the existing building rather than the original as the baseline. Reporting footprint while volume rises sharply. Treating screening as mitigation. Ignoring hardstanding, curtilage extension and outbuildings. And asserting that harm is limited without ever describing what openness on the site currently consists of.
A Green Belt case stands or falls on the description of the existing site. Write that first, with photographs and measurements, before you write a word about the proposal.
Most Green Belt applications need a Planning Statement that runs the openness assessment and the very special circumstances case as two separate arguments, and larger schemes need landscape and visual work alongside it. Browse the report types to see what a Green Belt site typically calls for.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
Is openness the same as visual impact?
No. Openness is the absence of built development, judged spatially as well as visually. The Supreme Court confirmed in Samuel Smith Old Brewery in 2020 that openness is not purely visual, and that visual effect is capable of being relevant but is a matter of planning judgement. Landscape character and visual amenity are separate considerations with their own tests.
Does screening a building with trees restore openness?
No, and inspectors say so regularly. Planting reduces how visible a building is while the land remains occupied by development. In some cases the planting itself encloses land that was previously open, which makes the position marginally worse rather than better. Screening is worth doing for visual reasons, not as an answer to openness.
What counts as the original building?
The building as it stood on 1 July 1948, or as first built if later, rather than as it stands today after previous extensions. Using the current building as the baseline is the most common technical error in Green Belt householder cases, and because it flatters the applicant, officers check it carefully against historic mapping and past permissions.
Do hardstanding and outbuildings affect openness?
Yes. Openness is affected by anything that takes land out of an undeveloped state, so parking areas, hardstanding, walls, gates, oil tanks, lighting columns and domestic paraphernalia all count. Assessments that consider only the main building understate the effect, and appeal decisions frequently pick this up.
Does a temporary permission reduce harm to openness?
It can reduce the weight given to the harm, because duration is part of the assessment, but it does not remove the harm. Mineral working is the standard example. If restoration is being offered as part of the case, secure it properly, normally through a planning obligation rather than optimistic condition wording.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.