Evidencing Green Belt openness in a planning application

The green belt openness test is not a landscape test and it is not a visual amenity test. Openness in planning terms means the absence of development, and the appeal courts have confirmed that it has both a spatial dimension and a visual one, with the weight given to each being a matter of planning judgement for the decision maker. That is the whole doctrine in two sentences. The difficulty is evidencing it, because an inspector asked to judge openness on a bare assertion will reach for the cautious answer.

This piece is about the evidence rather than the rule. If you need the underlying concept first, openness of the Green Belt and what the test means covers it.

Spatial and visual openness in the case law

The Court of Appeal in Turner accepted that openness is not purely a visual matter and that its spatial aspect, the presence or absence of built form, is central. The Supreme Court in Samuel Smith Old Brewery then held that the visual quality of the landscape is not in itself an essential part of openness, while confirming that visual effects are capable of being relevant depending on the facts.

Read together, the practical position is this. A decision maker must consider the spatial effect. They may consider visual effects where the circumstances make them material. They are not obliged to carry out a landscape assessment in every case.

That gives an applicant two distinct arguments to run, and they need separating in the drafting. Conflating them produces a statement that reads as landscape advocacy and invites the officer to dismiss the spatial case with it.

Factors that decisions actually weigh

Across appeal decisions and judgments, the same considerations recur.

The volume and footprint of built form, compared with what is there now. The spatial spread of development across the site, since a scattered layout affects openness differently from a compact one. The duration of the development and whether it is reversible, which is why temporary permissions and mineral workings are treated differently from permanent buildings. The degree of activity the use will generate, including vehicle movements, external storage and lighting.

Height matters, but less mechanically than people expect. A low, wide building can harm openness more than a taller, smaller one. Say so with numbers rather than adjectives.

Building the spatial evidence

The single most useful document in a Green Belt case is a comparative schedule. Set out the existing footprint in m², the existing volume in m³, the proposed footprint and volume, and the change in each, with the measurement convention stated. External measurements, from finished ground level, excluding below ground elements, is the convention most inspectors expect.

Then add three things officers rarely get and always use.

1. A site plan showing existing and proposed built form overlaid, at the same scale, with hardstanding and permanent external storage shown as built development rather than as landscape.
2. Cross sections through the site on the same datum, taken on the lines that matter for the nearest public vantage points.
3. A short table of any permitted development fallback, with the class relied on and the reason it is realistic and likely to be implemented.

The fallback point is underused. Where a lawful alternative would itself reduce openness, the comparison is not between the proposal and an empty field. It is between the proposal and what could be built anyway.

The five purposes, assessed separately

Harm to openness is one thing. Conflict with the purposes of including land in the Green Belt is another, and the two are assessed separately even though statements routinely merge them.

The purposes are to check the unrestricted sprawl of large built-up areas, to prevent neighbouring towns merging into one another, to assist in safeguarding the countryside from encroachment, to preserve the setting and special character of historic towns, and to assist urban regeneration by encouraging the recycling of derelict and other urban land.

Take each one in turn and say whether it is engaged. On most small sites, three of the five are not, and saying so directly is more persuasive than silence. Where encroachment into the countryside is the live purpose, address the relationship with the settlement edge and any defensible boundary, because that is the ground the officer will occupy.

Inappropriate development and the exceptions

Development that is inappropriate in the Green Belt is by definition harmful and should not be approved except in very special circumstances. The NPPF then lists the categories that are not inappropriate, including buildings for agriculture and forestry, proportionate extensions and alterations, replacement buildings that are not materially larger, limited infilling in villages, and the redevelopment of previously developed land subject to the stated tests.

Two cautions on citation. The Framework was renumbered in December 2024 and re-issued on 17 August 2026 with policy-coded chapters in place of paragraph numbers, so quote the edition you are relying on and check the current text on gov.uk before you file. And the grey belt concept introduced in December 2024 has its own tests, which need verifying against the version in force rather than against an older summary.

Where the proposal is an agricultural building, the analysis is different again and is dealt with in Green Belt and agricultural buildings.

Very special circumstances and the balance

If the development is inappropriate, substantial weight attaches to the harm to the Green Belt, and that harm plus any other harm must be clearly outweighed by other considerations.

Very special circumstances are not required to be unique. They are required to be sufficient. The mistake I see most often is a long list of ordinary planning benefits presented as though volume substitutes for weight. Four modest benefits do not add up to one substantial one.

What does carry weight, on the evidence of decided appeals, is a benefit that could not be delivered elsewhere, a demonstrable and quantified need, a fallback that is worse, and a reduction in harm compared with the existing position. Quantify each. An unquantified housing land supply argument is worth very little against substantial weight.

Appeal decisions are indicative of how inspectors have approached an issue rather than binding precedent, so use them to show an approach, not to claim an outcome. The practical route through a refusal is set out in Green Belt refusals and very special circumstances at appeal.

Recording the assessment in the statement

Give openness its own heading in the Planning Statement. Inside it, deal with the spatial effect first, with the comparative schedule cross-referenced. Then deal with visual effects, saying why they are or are not material on these facts. Then deal with each of the five purposes. Then, and only then, set up the balance.

Do not bury the volumetric increase in an appendix. If the proposal increases built volume by a third, say so in the second line and explain why the effect on openness is still limited. An officer who finds the number for themselves stops trusting the rest of the document.

Where visual effects are in play on the facts, a Landscape and Visual Impact Assessment gives the judgement a method rather than leaving it to competing adjectives.

Illustrative example: a replacement dwelling on a Green Belt plot, with the existing bungalow at 340m³ and the proposal at 430m³. The volumetric increase is about 26 per cent, the footprint is smaller, and the building sits 12m further from the lane behind existing planting. That case is arguable on materially larger. The same proposal with an attached double garage and a 200m² hardstanding is not.

Enter your postcode on PlanScope to see which reports a Green Belt proposal is likely to need.

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.