What "rounding off" actually means and what inspectors look for

"Rounding off" is one of those planning terms that appears in dozens of local plans, is rarely defined in any of them, and gets argued over in appeal after appeal. If you are advising on a site that sits just outside a settlement boundary, it is often the whole case.

This post sets out what the term means in practice, what inspectors actually test when they apply it, and where appellants most often go wrong.

It is a local plan concept, not a national one

The first thing to be clear about: rounding off appears nowhere in the National Planning Policy Framework. It is a creature of local plan policy, which means its meaning varies between authorities and you must read the specific wording that applies to your site.

What is consistent is the underlying idea. Most spatial strategies direct growth towards a hierarchy of main settlements. Rounding off is one of the limited circumstances in which development outside that hierarchy — and outside the built form of a smaller settlement — may still be acceptable, because it completes or tidies an existing edge rather than extending into open countryside.

That distinction, between completing an edge and extending into countryside, is what every rounding off appeal turns on.

The test inspectors apply

Where a local plan defines the term at all, the definition usually appears in supporting text rather than in the policy itself. Cornwall's is representative, and describes rounding off as development on land that is:

• substantially enclosed;
• outside the urban form of a settlement, but immediately adjoining or within it;
• bounded by an edge that is clearly defined by a physical feature or features;
• where that feature also acts as a barrier to further growth;
• and of a scale appropriate to the size and role of the settlement.

Read those criteria closely and something becomes apparent. Four of the five are about the physical characteristics of the site boundary. Only the last is about the development itself.

This is the single most useful thing to understand about rounding off appeals: they are usually won or lost on the boundary, not on the scheme.

What counts as a defined edge

In practice, inspectors have accepted a range of features as providing clear definition:

• mature hedgerows, particularly where dense and continuous;
• blocks of woodland or established tree belts;
• watercourses;
• roads, railway lines and other infrastructure;
• significant changes in level.

What matters is not merely that a feature exists but that it does two jobs at once: it must contain the site visually, and it must plausibly stop development going further. A boundary that reads as a pause rather than a full stop tends not to satisfy the test.

A worked example

The appeal at Land North of Fore Street, Probus (APP/D0840/W/25/3371943, allowed 22 May 2026) is a useful illustration, because the inspector set out her reasoning on each limb of the test.

The site was a field immediately behind housing fronting Fore Street. Probus is not one of Cornwall's main settlements, so the appellant relied on rounding off.

The council's position was that the site was not sufficiently enclosed. The inspector disagreed, finding that dense hedgerows and wooded areas along the northern, western and eastern boundaries provided clear definition and enclosure. Although the site sat outside the existing urban form, it had an edge defined by physical features that provided a barrier to further growth, and so met the rounding off criteria.

Two further points from that decision are worth noting, because both come up repeatedly.

The "thin end of the wedge" argument

A common council objection is that allowing one rounding off scheme creates the conditions for the next — the new development becomes the settlement edge, and the adjoining field becomes the new candidate for rounding off.

Inspectors take this seriously, and it is worth addressing directly rather than hoping it will not be raised. At Probus the inspector dealt with it explicitly, finding that the site's containment ensured a clear distinction from the field to the west, restricting visual and physical connectivity, so the proposal would not lead to the creation of a further site for rounding off.

If you are preparing a case, being able to demonstrate why your boundary is the last defensible one is often more persuasive than arguing the merits of the scheme.

Supplementary guidance is not development plan policy

Many authorities publish advice notes or SPDs elaborating on what rounding off requires. Cornwall's Chief Planning Officer's Advice Note on Infill and Rounding Off (December 2017) suggests such a site is "likely to be surrounded on at least two sides by existing built development".

At Probus the council relied on that. The inspector gave it limited weight, for three reasons: the word "likely" is not a prescriptive requirement; the advice note is guidance only and does not form part of the adopted development plan; and the note itself states that it should not be used as a reason for refusing an application.

The wider lesson is one worth carrying into any appeal. Where a refusal rests substantially on supplementary guidance rather than adopted policy, establishing the status of that guidance early can be decisive.

Where appellants tend to lose

Reviewing dismissed rounding off appeals, the failures cluster into a few recognisable patterns.

An open boundary on one side. Enclosure on three sides with the fourth open to fields is the most common reason for dismissal. The site reads as the start of an extension rather than the completion of an edge.

Scale disproportionate to the settlement. The principle may be accepted and the appeal still dismissed because the number of units is out of keeping with the size and role of the settlement. This limb of the test is easy to overlook when the boundary argument feels strong.

Boundaries that are recent or reversible. A hedgerow planted five years ago, or a fence, carries less weight than an established landscape feature. Historic mapping is useful here — though note that at Probus the inspector observed that while the site's boundaries followed medieval field patterns shown on the 1840 Tithe Map, the dense wooded areas relied on did not appear on that mapping. Age cuts both ways.

Treating rounding off as a presumption. Meeting the criteria establishes that the principle of development is acceptable. It does not dispose of character, heritage, highways or any other main issue.

What this means for a case

If you are advising on a site where rounding off is in play, the evidence that tends to matter most is evidence about the boundary: what the features are, how long they have been there, how continuous they are, what they look like from public vantage points, and why they represent a natural limit to growth.

That is a different exercise from the design and layout work that dominates most planning submissions — and at permission in principle stage, layout may be explicitly outside the scope of what the inspector will consider at all.

Finding relevant decisions

Rounding off is mentioned in a great many decisions and determinative in comparatively few. Searching the phrase returns everything that cites it in passing alongside the small number where it was the main issue.

On Plan Archive you can filter by the issues the inspector actually set out, so you see only the decisions that turned on the point — and, for each, which way it went and why.

Search rounding off decisions