Formation of ancillary building in residential curtilage

Appeal Decision Site visit made on 13 July 2026 by Claire Coles MRTPI an Inspector appointed by the Secretary of State Decision date: 16th September 2026 Appeal Ref: 6005088 Leydens Farm, Lydens Lane, Hever, Kent TN8 7EP • The appeal is made under section 78 of the Town and Country Planning Act 1990 (as amended) against a refusal to grant planning permission. • The appeal is made by Leydens Farm Ltd against the decision of Sevenoaks District Council. • The application Ref is 25/02484/HOUSE. • The development proposed is formation of ancillary building in residential curtilage. Decision 1. The appeal is dismissed. Preliminary Matters 2. The National Planning Policy Framework (the Framework) was revised during the course of the appeal. The Council and appellant were given the opportunity to comment on the revisions, however, no response was received from either party. 3. A Unilateral Undertaking (UU) under Section 106 of the Town and Country Planning Act 1990 (S106) was submitted with the application. This undertaking would ensure the pool building approved under reference 25/01208/HOUSE dated 31 July 2025 could not be erected should planning permission be granted for the ancillary building (named office building in the UU) the subject of this appeal. I have taken the UU into account in coming to my decision. 4. Whilst, in certain circumstances, a proposal can be amended through revised plans during an appeal, in line with the Wheatcroft principles1, I can see that there are substantial differences between the appeal proposal and that of the revised scheme. In this case, it is my view that the appeal must be determined on the basis of the plans as originally submitted to the Local Planning Authority (LPA) and upon which it based its decision, and which have been subject to consultation. To do otherwise would prejudice the interests of the LPA, interested third parties and consultees, who have not been consulted on the revised scheme and who may have observations to make. I have therefore proceeded to determine the appeal on the basis of the plans as originally submitted. The merits of the revised scheme would, if necessary, be a matter for the main parties to consider as part of a fresh proposal away from this appeal. Main Issues 5. The main issues are: 1 Bernard Wheatcroft Ltd v Secretary of State for the Environment (JPL, 1982, P37) Appeal Decision 6005088 2 • Whether the development comprises inappropriate development in the Green Belt having regard to the Framework and any relevant development plan policies; • The effect of the development on the openness of the Green Belt and the purposes of including land within it; • The effect of the development on the natural beauty of the High Weald National Landscape; • Whether there are other considerations weighing in favour of the development; and • Whether the harm by reason of inappropriateness, and any other harm, is clearly outweighed by other considerations. If so, does this amount to the very special circumstances required to justify the proposal. Reasons Whether the development comprises inappropriate development in the Green Belt having regard to the Framework and any relevant development plan policies. 6. Policy GB7 of the Framework identifies development which is not inappropriate in the Green Belt. Policy GB7 b identifies the following as not inappropriate: ‘the reuse, extension, alteration or replacement of an existing building, provided that the existing building is of permanent and substantial construction, is lawful in planning terms, and any extension or alteration will not result in a disproportionate increase in size compared to the original building. In the case of proposals for a replacement building, it should be for the same use and not materially larger than the one it replaces’. 7. The proposed development would not reuse, extend or alter an existing building. Planning permission was granted for the erection of a pool building (ref: 25/01208/HOUSE) in 2025. The pool building has yet to be erected. The appeal is accompanied by a Unilateral Undertaking (UU) under Section 106 of the Town and Country Planning Act 1990 which would prevent the construction of the pool building approved by the Council should the appeal be allowed. 8. The replacement of the pool building with the outbuilding would not comply with Policy GB7 b of the Framework as the outbuilding would not be in the same use as the pool building (although they are both proposed as ancillary outbuildings). Although within the residential curtilage, the size and scale of the proposed outbuilding mean this would not be ancillary in function with three offices, a kitchen, male and female toilets and a waiting area. The similarities between the proposal, and the office building refused under appeal ref: APP/G2245/C/21/3271033 suggests the building is likely to be used, at least in part, by the commercial uses on the site. 9. The proposed development would not meet the criteria in Policy GB7 of the Framework which identifies development which is not inappropriate in the Green Belt. 10. Policy GB3 of the Sevenoaks Allocations and Development Management Plan (ADMP) states that outbuildings located more than 5m from the existing dwelling Appeal Decision 6005088 3 will be permitted where the building, including the cumulative impact of other outbuildings and extension within the curtilage of the dwelling, would be ancillary to the main dwelling in terms of function and design and would not materially harm the openness of the Green Belt. The appellants state the proposed outbuilding would be an ancillary outbuilding, however, I have already identified that the building is likely to be used, at least in part, by the commercial uses on the site and would be unlikely to be ancillary to the main dwelling in terms of function. The appellants have suggested the outbuilding could be the subject of a restrictive condition limiting its use to ancillary to the main dwelling, however, I am not convinced that a restrictive condition would outweigh the harm to the openness of the Green Belt. Even if I were satisfied of this, a restrictive condition would not meet the criteria set out in Policy DM6 of the Framework as it would not be relevant to the development as the outbuilding would be functionally more akin to a commercial use rather than an ancillary outbuilding. 11. The Green Belt Supplementary Planning Document (SPD) provides further guidance on development in the Green Belt and states that in order to minimise the impact of outbuildings on the openness of the Green Belt, the Council will seek to restrict any outbuildings to a limit of 40sqm. The proposed outbuilding would have a footprint which is significantly larger than recommended in the SPD. Whilst it is acknowledged that the supporting text in the SPD does not carry the same weight as Policy, it is indicative of the size threshold considered acceptable by the Council for outbuildings within the Green Belt. 12. In conclusion, for the reasons identified above, the proposal would be inappropriate development in the Green Belt, contrary to Policy GB3 of the ADMP, Section 5 of the SPD and Policy GB7 of the Framework. The effect of the development on the openness of the Green Belt and the purposes of including land within it. 13. Leydens Farm is located within the open countryside and comprises a group of buildings accessed via a long drive from Lydens Lane. The buildings comprise a number of former farm buildings that are now used for a car sales business, including repair and restoration facilities, equestrian facilities and residential dwellings. A public footpath runs alongside the buildings from Lydens Lane and continues through the fields beyond Leydens Farm. 14. The orientation and location of the proposed outbuilding would spread development within the confines of the residential curtilage (which also includes a tennis court and a swimming pool) further to the rear of the appeal site, encroaching into the open gardens and fields behind the house. I note the retention of the hedging providing screening from the public footpath of the proposed development, and that the hedging could be retained by condition, however, openness can be perceived visually and spatially and factors to be considered include the duration of the development and its ability to return to its original state as well as the degree of activity to be generated. 15. The scale of the proposal would visually and spatially encroach into the openness of the Green Belt and if the outbuilding were to be occupied to its full potential, would result in a significant level of activity at the building. 16. The pool building the subject of permission 25/01208/HOUSE, which the appellant is suggesting would not be built if this appeal were allowed, is larger in terms of Appeal Decision 6005088 4 footprint and volume than the appeal proposal. Both proposals would be located within the residential curtilage and screened by the hedging, however, in terms of the effect on the openness of the Green Belt, the appeal proposal would have a greater effect on openness as it would be located further from the cluster of residential buildings on the site and would extend built development to the southeast, encroaching further into the Green Belt. 17. The purposes of the Green Belt include safeguarding the countryside from encroachment. Given the relative relationship between the proposed pool building and proposed outbuilding with the other farm buildings, the proposed outbuilding encroaches considerably more into the countryside than the proposed pool building. Consequently, the development would not safeguard the countryside from encroachment. 18. For these reasons, I conclude the proposed outbuilding, even taking into account the UU preventing the pool building being built, would result in harm to the openness of the Green Belt and the purposes of including land within it. As a result, it is contrary to the Framework which seeks to keep land permanently open and safeguard the countryside from encroachment. The effect of the development on the landscape and scenic beauty of the High Weald National Landscape (HWNL). 19. The appeal site is located within the HWNL. Policy EN5 of the ADMP provides the highest status of protection to the HWNL in relation to landscape and scenic beauty. The Framework states that substantial weight should be placed on the importance of conserving and enhancing the natural beauty of these areas. The Levelling-up and Regeneration Act (2023) amended Section 85 of the Countryside and Rights of Way (CROW) Act, to create a new duty on planning authorities to ‘seek to further the purpose of conserving and enhancing the natural beauty of the area’ when considering developments in National Landscapes. The new duty replaces the previous requirement for relevant authorities to ‘have regard’ to the purpose of National Landscapes and is intended as a more proactive and strengthened requirement. 20. The HWNL comprises small fields and woodlands with groups of agricultural or former agricultural buildings and settlements in a hilly landscape. 21. The proposed outbuilding comprises a substantial, single storey timber clad building with casement windows and gable ended porch over the steps to the glazed front entrance. The scale, layout and materials of the building reflect the appearance of an agricultural building to some extent. However, the windows and porch result in a more commercial appearance. 22. The proposal extends built development at Leydens Farm further to the southeast in the residential curtilage. This is a limited incursion of built development into the National Landscape, but the proposal would have a commercial appearance and nature. Taking account of this, the proposal affects the landscape and scenic beauty of the area. 23. The proposed building would be likely to be visible in closer views, although it is acknowledged additional planting could be provided and retained by condition. Despite this, the screening would not wholly overcome the effect of the building on Appeal Decision 6005088 5 the natural beauty of the area, even taking into account the trade off with the pool building. 24. For these reasons, I conclude that the proposal would not conserve and enhance the natural beauty of the area. As such, it is contrary to Policy EN5 of the ADMP and the Framework that seek to protect the landscape and scenic beauty of the National Landscape, and conserve and enhance the character of the landscape. Other considerations 25. The appellant suggests that an alternative outbuilding could be built under permitted development, but I have little evidence to support this claim. I am therefore unable to conclude that this offers a realistic or probable prospect and consequently does not represent a legitimate fallback position. It is open to the appellant to have the matter determined under Sections 191 or 192 of the Town and Country Planning Act 1990. Any such determination would be unaffected by the outcome of this appeal. I have therefore considered the appeal on the basis of what is proposed and its consequent effects. Conclusion 26. I have found that the proposed outbuilding, even taking account of its proposed replacement of the pool building, would not comprise appropriate development in the Green Belt as defined by Policy GB3 of the ADMP and the Framework. It would harm the openness of the Green Belt and conflict with the purposes of including land within it. In addition, it would not conserve and enhance the natural beauty of the High Weald National Landscape. 27. Taking all matters put to me into account, the substantial weight to be given to Green Belt harm and any other harm is not clearly outweighed by other considerations, either individually or cumulatively, sufficient to demonstrate very special circumstances. Therefore, the proposed outbuilding is contrary to Policies GB3 and EN5 of the ADMP and the Framework that seek to protect the Green Belt from inappropriate development. 28. For these reasons, I conclude that the development does not accord with the development plan and is dismissed. Claire Coles INSPECTOR