Construction of garden room (RETROSPECTIVE)

Appeal Decision Site visit made on 12 March 2026 by F BA (Hons) MRTPI Decision by A Edgington BSc (Hons) MA CMLI an Inspector appointed by the Secretary of State Decision date: 21 July 2026 Appeal Ref: 6002612 Mackleys, Oakley Road, Bromley BR2 8HG • 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 Mrs J Cao against the decision of the Council of the London Borough of Bromley. • The application Ref is 25/01739/FULL6. • The development proposed is described as the “construction of garden room (RETROSPECTIVE)”. 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. Preliminary Matters 3. The other appeal on the site regarding an “outbuilding to rear garden (RETROSPECTIVE)”, reference 6002641, is the subject of a separate decision. 4. The development has been completed, and in the interests of clarity this appeal has been considered on the basis of plan no. 2025/20. It is noted that there is a discrepancy between the application form, which refers to a 27sqm increase in gross floor area, and the submitted plans, which show an increase from approximately 27sqm to 34sqm. The Council has assessed the application on the basis of the plans, and I see no reason to do otherwise. Main Issue 5. The main issues are: • Whether the proposal would be inappropriate development in the Green Belt having regard to the National Planning Policy Framework (the Framework) and any relevant development plan policies; • The effect of the development on the openness of the Green Belt; and, • Whether any harm by reason of inappropriateness, and any other harm, would be clearly outweighed by other considerations, so as to amount to the very Appeal Decision 6002612 2 special circumstances required to justify the proposal. Reasons for the Recommendation Inappropriate development 6. The plans show that the development comprises two small outbuildings that have been combined to form one garden room. The Framework establishes that development within the Green Belt should be regarded as inappropriate unless one of the specified exceptions applies. The appellant and Council refer to the development in the context of the exceptions set out in Paragraph 154 (c) and (d), which are concerned with extensions and alterations to a building, and replacement buildings respectively. Policy 49 of the Bromley Local Plan (2019) (the LP) sets out the same criteria and overall approach to development in the Green Belt. Paragraph 154 c) – Extension and alteration of a building 7. Paragraph 154 c) of the Framework states that development is not inappropriate if it is 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. The Framework is silent as to what disproportionate means and it is therefore a matter of judgement. The courts have held that a detached outbuilding should not be excluded from being an extension to a dwelling, and this should be considered in terms of its “normal domestic adjunct” to the host dwelling which could include its purpose, use, relationship to the building, and its size. It is again therefore a matter of judgement as to whether development should be considered as an extension of the host dwelling. 8. The appellant has stated that the garden room is an extension of the host dwelling. The plans indicate that the pre-existing structures were set in close proximity to the associated dwelling. As such, given their use as domestically adjunct to the host dwelling, I conclude that the development can be considered an extension of the host dwelling for the purposes of Paragraph 154 c) of the Framework. 9. However, the Framework sets out that the original building is taken to be the size of the building on 1 July 1948, or, if constructed after that date, as it was built originally. The dwelling’s planning history lists a series of extensions to the host dwelling. These include “front and rear dormer extensions” and a “two storey rear extension and single storey side extension”. From my visit, it appeared these works had been carried albeit with the latter replacing the single storey rear extension. The extensions represent considerable additions to the original host dwelling in terms of their volume and floor space. The original dwelling has already been significantly extended. As such, extending and altering the two former outbuildings to form a garden room, which in itself increases the floor area of those two outbuildings by some 30 per cent, amounts to disproportionate additions over and above the size of the original building. The development does not meet the criterion set out in Paragraph 154 c) and is inappropriate development. 154 d) – Replacement building 10. Paragraph 154 d) sets out that development is not inappropriate if it is the replacement of a building, provided the new building is in the same use and not materially larger than the one it replaces. The former outbuildings were separated Appeal Decision 6002612 3 by a modest gap. Given their proximity to each other it seems reasonable to consider them as one building for the purposes of this exception. 11. However, the total footprint has increased by around 30 per cent. Furthermore, the plans before me indicate that the two buildings had been used as stores, whereas what is before me is a garden room. Accordingly, the garden room is not in the same use and is materially larger than the buildings it replaced. The exception criterion set out in Paragraph 154 d) is therefore not met and the outbuilding is inappropriate development. Openness 12. As set out in the Framework, the fundamental aim of Green Belt policy is to prevent urban sprawl by keeping land permanently open. The development has increased built development by enlarging one of the outbuildings and filling a narrow gap between the two former structures. The development would largely be perceived as a consolidation of existing built form. Consequently, whilst there would be some erosion of openness arising from the increased footprint and slightly greater visual presence of the buildings, I consider that minor weight should be given to harm to openness. 13. Nonetheless, the garden room is inappropriate development in the Green Belt and would have an adverse effect on openness. There would be conflict with Policies 49 and 51 of the Local Plan (LP), Policy G2 of the London Plan (2021), and the approach of the Framework which, amongst other things, seek to protect the Green Belt from inappropriate development. Moreover, the development would conflict with the purposes of the Green Belt, in its openness and permanence. 14. The Council cites LP Policy 37 within the decision notice. However, this policy appears to relate primarily to the general design of development, and such is not determinative to the main issue within this appeal. Other considerations 15. The appellant notes that the site has been the subject of a number of Certificates of Lawful Development (CLD). Whilst this may be the case, there is nothing before me to indicate that the garden room has a CLD or that the combined outbuildings that now form the garden room are permitted development. As such, there is no realistic fall-back before me. Other matters 16. The loss of openness arising from a development is not based on the character and appearance of surrounding land and in any case the identified harm has been given minor weight only. 17. Soft landscape features can change over time, and the inappropriateness of development in the Green Belt and accompanying harm to openness is based on the requirements set out in the Framework, not views. Similarly, the diversity of the garden hinterland is not determinative. Green Belt Balance, Conclusion and Recommendation 18. 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 Appeal Decision 6002612 4 special circumstances. It further requires that substantial weight be given to any Green Belt harm. “Very special circumstances” will not exist unless the harm to the Green Belt by reason of inappropriateness, and any other identified harm, is clearly outweighed by other considerations. 19. There are no other considerations that would clearly outweigh the harm to the Green Belt by reason of inappropriateness and loss of openness. Consequently, the very special circumstances necessary to justify the proposed development do not exist. As such, the development would be contrary to the development plan. I therefore recommend that the appeal is dismissed. Finlay Bradford APPEAL PLANNING OFFICER Inspector’s Decision 20. I have considered all the submitted evidence and my representative’s report and on that basis the appeal is dismissed. A Edgington INSPECTOR