A barn conversion appeal for four homes at Hogs Back Farm Yard near Guildford has been dismissed. The Inspector found too many problems with the proposal, even though Guildford has a serious shortage of land available for new housing. If you’re looking at converting farm buildings, I would pay close attention to this decision because it shows why an apparently promising scheme can still fail.
In the barn conversion appeal, Inspector C Walker found the proposal would be inappropriate development in the Green Belt, would harm the Surrey Hills National Landscape, lacked secure mitigation for the Thames Basin Heaths Special Protection Area and had not shown that the proposed self-build homes could lawfully rely on the biodiversity net gain exemption.
The decision, appeal 6009810 dated 6th October 2026, is particularly useful because the Inspector also tested the grey belt rules in the August 2026 National Planning Policy Framework (NPPF). Although the site qualified as grey belt, that did not mean homes could automatically be approved there. Its isolated rural location failed a separate test about access to everyday services, which is an important distinction if you’re considering a similar proposal.
Why the barn conversion appeal failed
The barn conversion appeal concerned an application for full planning permission to convert existing barns at Hogs Back Farm Yard, Monkshatch, Compton, into two pairs of semi-detached dwellings. The Inspector corrected the application description, which had referred to two dwellings rather than four.
The site sits within the Green Belt and the Surrey Hills National Landscape, and also falls within the 400 metre to 5 kilometre zone of influence around the Thames Basin Heaths Special Protection Area.
Those designations meant the barn conversion appeal was never going to turn on a single issue. The Inspector identified six main questions: habitat effects, landscape character, access to services, biodiversity net gain, Green Belt policy and whether any other considerations amounted to very special circumstances.
The full appeal decision for 6009810 is hosted by Planning Geek. The Planning Inspectorate record confirms the appeal reference and decision status.
SPA mitigation was not secured
In the barn conversion appeal, the Inspector found that four additional homes, taken together with other development, would be likely to increase recreational pressure on the Thames Basin Heaths SPA.
Guildford’s avoidance strategy provides a route for mitigating that pressure through financial contributions towards measures such as suitable alternative natural greenspace, access management, signage and awareness work.
The appellant accepted that a contribution was required. The problem was that no effective mechanism was before the Inspector to secure it.
Without that certainty, the Inspector could not conclude that the adverse effect on the integrity of the SPA would be avoided or mitigated. A planning condition was not considered an appropriate substitute and no planning obligation had been provided.
That point alone carried major weight. Under the habitats regime, a decision-maker needs the necessary confidence that harm to the protected site has been addressed before permission can be granted.
BNG exemption was not enough to say the homes were self-build
The application form said the dwellings would be self-build or custom-build and therefore exempt from the statutory biodiversity gain condition.
The Inspector did not simply accept the label. The Biodiversity Gain Requirements (Exemptions) Regulations 2024 tie the exemption to the statutory meaning of self-build or custom housebuilding. The homes therefore needed to be secured in a way that satisfied that definition.
The parties disputed whether the initial owners would have sufficient primary input into the final design and layout. More fundamentally, however, the Inspector found that there was nothing before the appeal to secure the homes as self-build or custom-build dwellings.
A condition was not considered sufficiently enforceable and there was no planning obligation.
Because the proposal could not safely be treated as exempt, the Inspector then looked at the scheme as market housing. The normal minimum BNG information had not been submitted because the applicant had proceeded on the basis of an exemption.
The result was a difficult evidential gap: the Inspector could not be satisfied that the statutory biodiversity gain condition would be capable of being discharged.
Planning Geek has already reported another recent appeal where a self-build undertaking was accepted for BNG purposes. The contrast is useful. Calling a scheme self-build is not enough; the planning mechanism securing that status matters.
Why the farm buildings did not qualify as previously developed land
In the barn conversion appeal, the appellant also argued that the site should benefit from the Green Belt exception for redevelopment of previously developed land.
The Inspector rejected that route. The evidence indicated that the buildings had last been used for agriculture, and the NPPF definition of previously developed land excludes land occupied, or last occupied, by agricultural or forestry buildings.
There was no evidence showing that the buildings had acquired another lawful use which would take the site outside that exclusion.
This is where the site’s recent planning history is particularly interesting. A separate appeal at the same farm, reference 6012900, sought prior approval for the agricultural buildings to move to a flexible commercial use under Class R, the permitted development right in Part 3 of the General Permitted Development Order.
That appeal was dismissed on 30th September because the red-line area was treated as curtilage far beyond the Class R limit. Planning Geek reported the decision in Class R trap: 3,100 m² red line sinks Guildford farm appeal.
The later residential appeal therefore arrived without a successful intervening commercial use that could have changed the planning position.
Could the barns be reused under Green Belt policy?
The appellant had another Green Belt argument. Policy GB7(1)(b) of the August 2026 NPPF can allow the reuse, extension or alteration of an existing lawful building where it is of permanent and substantial construction.
On the drawings, much of the existing external form appeared capable of being retained. But the appeal evidence did not include a structural survey or engineering appraisal showing that the barns could genuinely be converted without substantial rebuilding.
The Inspector’s site visit did not help the appellant. One roof was being propped and the other barn had lost its roof, with supporting trusses having collapsed inwards.
The burden was on the appellant to show that the exception applied. The Inspector concluded that the evidence did not establish that the buildings remained of substantial construction.
Nor was that something which could sensibly be left to a later planning condition. Whether the structures could genuinely be converted went to the principle of the Green Belt exception itself.
Grey belt definition passed, sustainable location failed
The barn conversion appeal decision also applies the revised August 2026 grey belt policy.
The parties agreed that the site did not strongly contribute to the relevant Green Belt purposes, and the Inspector noted an important change from the previous NPPF. The former exclusion relating to land affected by policies for assets such as National Landscapes and European habitat sites had fallen away.
As a result, the Inspector found that the site met the definition of grey belt.
That did not make the development acceptable. The grey belt exception in Policy GB7(1)(g) requires all of its criteria to be satisfied.
Guildford could not demonstrate a five-year housing land supply, so that part of the test favoured the appellant. The scheme was also not major development, meaning the Golden Rules did not apply.
The difficulty was location. The farm lies outside a settlement, reached by a narrow, unlit access without footways. Evidence of realistic walking, cycling and public transport options was weak.
The Inspector found future occupiers would be likely to rely predominantly on private cars and that the development therefore failed the sustainable-location requirement.
I’d treat that grey belt finding as a starting point, not a green light. Even when the land meets the definition, you still need evidence that the proposal passes the other policy tests, particularly whether people can realistically reach everyday services without depending on a car.
Housing need carried substantial weight but did not rescue the scheme
Guildford’s 2.98-year housing land supply gave the four proposed homes real weight. The Inspector described the housing contribution as valuable and attached substantial positive weight to it.
There were also moderate benefits from bringing deteriorating buildings back into use, construction activity and future local spending.
Those benefits were nevertheless outweighed by the collection of harms. The Inspector gave substantial weight to inappropriate Green Belt development and landscape harm, and the strongest weight to the unresolved effect on the protected habitat site.
The unsustainable location and unresolved BNG position added further conflict.
The barn conversion appeal was therefore dismissed. The Inspector found that the development conflicted with the development plan as a whole and that the other considerations did not amount to the very special circumstances needed to justify the proposal.
What practitioners should take from the decision
The value of appeal 6009810 is not that it creates a new legal rule. It is an Inspector’s decision, not court case law.
Its usefulness is evidential. A rural conversion can have several apparently plausible routes through policy, but each route needs the right proof. Here the appellant needed a mechanism for SPA mitigation, a robust way of securing self-build status, sufficient BNG information if that exemption failed, and evidence that the barns were actually capable of conversion.
The grey belt finding is also worth noting. Even after the site cleared the revised definition, sustainable location remained a separate gateway and proved fatal.
For anyone assessing redundant agricultural buildings, the practical message is simple: do not rely on the existence of the building itself. Establish the lawful use, structural capability, Green Belt route, biodiversity position, habitat mitigation and access evidence before choosing the planning strategy.
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