Creation of an eco-roof over existing swimming pool for use as a walipini greenhouse

Appeal Decision Site visit made on 19 May 2026 by Scott Wilson LL.B. MSc MRTPI Decision by L McKay MA MRTPI an Inspector appointed by the Secretary of State Decision date: 9 July 2026 Appeal Ref: 6006271 Trinity House, Burrows Lane, Gomshall, Surrey GU59QE  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 Carol Myson against the decision of Guildford Borough Council.  The application Ref is 25/P/01205.  The development proposed is the creation of an eco-roof over existing swimming pool for use as a walipini greenhouse. Decision 1. The appeal is dismissed. Appeal Procedure 2. The site visit was undertaken by a representative of the Inspector whose recommendation is set out below and to which the Inspector has had regard before deciding the appeal. Main Issues 3. The appeal site is within the Green Belt and so the main issues are:  Whether or not the proposed development would be inappropriate development in the Green Belt, having regard to the National Planning Policy Framework and any relevant development plan policies.  The effect of the proposed development on the openness of the Green Belt.  If the proposed development is inappropriate development, whether the harm by reason of inappropriateness, and any other harm, is clearly outweighed by other considerations so as to amount to the very special circumstances required to justify the proposed development. Reasons for the Recommendation 4. The appeal site comprises a two-storey detached and extended dwelling set within generous grounds. A detached double garage is positioned to the side of the dwelling, and an in-ground swimming pool with tiled walls and hardstanding surrounds is located within the rear garden. At the time of my site visit, which I recognise represents only a snapshot in time, the pool contained stagnant brown water with visible algal growth and was being used by wildlife. The site lies on the eastern side of Burrows Lane, outside the defined settlement boundary of Gomshall, and is situated within the Green Belt, the Surrey Hills National Appeal Decision 6006271 2 Landscape, and an Area of Great Landscape Value (AGLV), giving the surroundings a distinctly rural character. Whether or Not Inappropriate Development 5. The National Planning Policy Framework (2024) (the Framework) identifies that the fundamental aim of Green Belt policy is to prevent urban sprawl by keeping land permanently open. The Framework outlines that the construction of new buildings should be regarded as inappropriate in the Green Belt subject to several exceptions as set out in paragraph 154. 6. The Guildford Borough Local Plan: Strategy and Sites (adopted by Council on 25 April 2019) (the Local Plan) Policy P2 is consistent with the Green Belt aims of the Framework in terms of acknowledging that the construction of new buildings in the Green Belt will constitute inappropriate development, unless the buildings fall within the list of exceptions identified by the Framework. 7. The Framework paragraph 154c) allows for the extension or alteration of a building provided that it does not result in disproportionate additions over and above the size of the original building. That is defined as the building as it existed on 1 July 1948 or, if built after that, as it was when built. 8. The swimming pool is a structure ancillary to the use of the dwelling, and as such having regard to case law could be considered as part of the dwelling. The dwelling has been extended in various ways, and the appellant does not dispute the Council’s calculation that this has resulted in an increase in floorspace of approximately 107% over and above the original building. The proposal would increase this further to approximately 161%. This is a significant increase in floorspace terms. 9. It is however necessary to consider other factors, including the size and bulk of the proposal. Currently, the swimming pool has very little visual impact, being below ground on a sloping site behind the dwelling. The proposed roof would be relatively low but would nevertheless project well above ground level and would be a noticeable addition changing the profile of the sloping ground, even with the blending effect of the proposed green roof. Consequently, it would add to the bulk and amount of built form on the site. Overall, therefore, considering various factors the proposal would amount to a disproportionate addition over and above the size of the original dwelling. 10. The appellant has suggested that the swimming pool is a structure in its own right. Even if the swimming pool is considered as the original building, the addition of a roof over the entirety of the structure would result in a significant and disproportionate increase in its size and bulk. Consequently, even on that basis it would not fall within the exception in Framework paragraph 154c). 11. I note the examples of other extensions approved by the Council in the local area. However, these date from 2005 and 2011 respectively and were considered under a different policy context. The Council found them to be disproportionate additions in both cases. The reports provided also demonstrate that the relevant policy allowed for small extensions in some circumstances even where dwellings had previously been extended. The scale of extensions proposed in both cases was small, significantly less in percentage terms than is proposed here. Consequently, Appeal Decision 6006271 3 those examples are not comparable in effect or circumstances to the scheme before me and do not justify the scale of additions proposed here. 12. There is some dispute whether the proposal would constitute an engineering operation within paragraph 154h). There is nothing before me to suggest that the internal level of the pool is to be lowered, or that any new retaining structure or other engineering operations would be required to construct the proposal. I note that the uncertainty in a previous officer report related to a lawful development application where the plans appear to have been less detailed than what is currently before me. 13. The Town and Country Planning Act 1990 (as amended) defines a building operation as including demolition, rebuilding, structural alterations or additions to buildings and other operations normally carried on by a person in business as a builder. From the evidence before me it appears that the construction of a roof structure would be a building operation. Therefore, the proposal would not fall within the exception in Framework paragraph 154h). 14. Therefore, the proposal would not fall within any of the exceptions listed in paragraph 154 of the Framework. As such, the development would constitute inappropriate development in the Green Belt and would therefore be harmful, which is a matter to which I must afford substantial weight in the planning balance. Openness 15. The Framework outlines that one of the essential characteristics of Green Belts is their openness. Openness has both a spatial and a visual aspect. By its very nature of placing built development where there is currently none, the proposed development cannot fail but to have a greater impact on the openness of the Green Belt in spatial terms. I find that considering the overall size and scale of the development, and despite its limited height, the harm to the openness of the Green Belt from a spatial aspect would be moderate. 16. The proposal comprises a structure measuring approximately 1.73 metres (m) above ground level, 5.68 metres in width and around 12 metres in length, a matter which is not disputed between the parties. Whilst it would incorporate a long, curved living green roof which, from certain viewpoints, would present as a vegetated slope assimilating with the site’s topography, from other aspects it would appear as a domestic structure due to the presence of windows. As such, the development would introduce a discernible increase in size, scale, and bulk, adding to the overall extent of built form on the appeal site and materially affecting its visual perception. 17. The proposed structure would appear to encroach further into the open countryside, despite its sub-terranean design, rear garden location with limited public viewpoints, the use of high quality materials and an eco-roof. This scenario would be more harmful than already exists. I therefore find that there would be moderate harm to the openness of the Green Belt from a visual point of view. 18. I consider that the effect on the openness of the green Belt would be moderate, and I therefore give this harm moderate weight. Appeal Decision 6006271 4 Other Considerations 19. Paragraph 153 of the Framework states that inappropriate development is, by definition, harmful to the Green Belt and should not be approved except in very special circumstances. Stating that very special circumstances will not exist unless the harm to the Green Belt by way of inappropriateness, and any other harm, is clearly outweighed by other considerations. 20. The development in this case amounts to inappropriate development in the Green Belt and the Framework requires that substantial weight be attached to the harm in that regard. It would also cause moderate harm to the openness of the Green Belt. 21. I acknowledge that the development would provide year round opportunity to grow plants for the occupants of the property. However, such personal circumstances seldom outweigh general planning considerations, and I therefore give them limited weight in the appeal. 22. I acknowledge that the proposal would have no adverse impact on neighbouring occupiers; would support biodiversity and sustainable design principles; and would preserve the character of the site, the wider landscape, and the National Landscape and AGLV setting. However, these are neutral factors that would not outweigh the harm I have identified. 23. Whilst there were no objections from interested parties or the Parish Council, this does not amount to support for the scheme, and I afford this matter little weight. Green Belt and Planning Balance 24. The proposal would constitute inappropriate development in the Green Belt. When considered as a whole, moderate harm would be caused to the openness of the Green Belt. The substantial weight to be given to the cumulative Green Belt harm arising from the proposal would not be clearly outweighed by the other considerations as outlined above. Consequently, the very special circumstances necessary to justify the development do not exist. 25. Therefore, the proposed development would not accord with Policy P2 of the Local Plan, the Green Belt aims of the Framework, or the guidance in the Green Belt Supplementary Planning Document. 26. There are no other material considerations that justify granting permission for development contrary to the development plan. Conclusion and Recommendation 27. For the reasons given above and having had regard to all other matters raised, I recommend that the appeal should be dismissed. Scott Wilson APPEAL PLANNING OFFICER Appeal Decision 6006271 5 Inspector’s Decision 28. I have considered all the submitted evidence and my representative’s report and on that basis the appeal is dismissed. L McKay INSPECTOR