Basement extension and associated level changes to create indoor swimming pool

Appeal Decision Site visit made on 20 November 2018 by Lynne Evans BA MA MRTPI MRICS an Inspector appointed by the Secretary of State Decision date: 05 December 2018 Appeal Ref: APP/N5090/D/18/3210791 Edgehill Manor, Highwood Hill, London NW7 4HP  The appeal is made under section 78 of the Town and Country Planning Act 1990 against a refusal to grant planning permission.  The appeal is made by Mr & Mrs P Agarwal against the decision of the Council of the London Borough of Barnet.  The application Ref: 18/2929/HSE dated 14 May 2018, was refused by notice dated 12 July 2018.  The development proposed is basement extension and associated level changes to create indoor swimming pool. Decision 1. The appeal is allowed and planning permission is granted for basement extension and associated level changes to create indoor swimming pool at Edgehill Manor, Highwood Hill, London NW7 4HP in accordance with the terms of the application, Ref 18/2929/HSE dated 14 May 2018 subject to the following conditions: 1) The development hereby permitted shall begin not later than 3 years from the date of this decision. 2) The development hereby permitted shall be carried out in accordance with the following approved plans: 080908/02 B; 080908/03 C; 080908/ 04 B; 080908/05. 3) The materials to be used in the construction of the external surfaces of the development hereby permitted shall accord with those set out on the application form. 4) No site works or works on the development hereby permitted shall be commenced before arboricultural and construction method reports have been submitted to and approved in writing by the Local Planning Authority. The submitted details shall accord with BS 3998 British Standard for Tree Work and BS 5387 Trees in relation to Design, Demolition and Construction (or an equivalent British Standard if replaced) and shall include: i) the position of existing trees including in relation to existing and proposed ground levels, ii) any proposed pruning, felling or other works to these trees, iii) the siting of and details of temporary tree protection fencing, iv) construction method statements including construction routes. Appeal Decision APP/N5090//D/18/3210791 2 The works shall be undertaken in accordance with the approved details and the fencing shall be erected in accordance with the approved details before any equipment, machinery or materials are brought onto the site for the purposes of the development, and shall be maintained until all equipment, machinery and surplus materials have been removed from the site. Nothing shall be stored or placed within any fenced area, and the ground levels within those areas shall not be altered, nor shall any excavation be made, without the prior written consent of the Local Planning Authority. Preliminary Matters 2. The revised National Planning Policy Framework (Framework 2018) came into force on 24 July 2018 and from that date policies within the Framework 2018 are material considerations which should be taken into account in decision making. From reading all the information before me from the Appellant and the Council, I am satisfied that the revised Framework 2018 carries forward the main policy areas from the earlier Framework, as relevant to this appeal. 3. The Council’s questionnaire indicates that there are no tree preservation orders relating to the appeal property. However, the arboricultural report by Jonathan Mills which appears to have been undertaken on behalf of the Council refers to a number of tree preservation orders relating to the property. The Appellant has also submitted information in respect of the existing trees which I have taken into account in my decision. Main Issues 4. The main issues in this appeal are: a) Whether 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; b) Its effect on the character and appearance of the local area, with specific regard to its location within designated heritage asset of the Mill Hill Conservation Area. Reasons Issue a) Whether inappropriate development 5. The appeal property is a substantial detached house set in extensive grounds on the southern side of Highwood Hill (A5109). It is situated within the Metropolitan Green Belt (Green Belt) and within the Mill Hill Conservation Area. To the rear of the property is a large terrace, leading to a formal area of garden and onto a more informal garden and wooded area to the rear and to the side. The proposal relates to the provision of a basement indoor swimming pool under the existing terrace, with changes to the garden levels to the rear of the terrace. 6. The Framework 2018 sets out the government’s planning policies to secure sustainable development. Paragraph 133 sets out the great importance that the Government attaches to Green Belts and that the essential characteristics of Green Belts are their openness and their permanence. Paragraph 143 confirms that inappropriate development is by definition harmful to the Green Belt and Appeal Decision APP/N5090//D/18/3210791 3 should not be approved except in very special circumstances. Paragraph 145 sets out that the construction of new buildings is inappropriate except for a limited number of exceptions including the extension or alteration of a building providing that it does not result in disproportionate additions over and above the size of the original building. The Framework does not define further the term ‘disproportionate’. 7. Policy 7.16 of the London Plan relating to the Green Belt seeks to protect the Green Belt in accordance with national policy and Policy CS7 of Barnet’s Local Plan Core Strategy seeks to enhance and protect Barnet’s open spaces including the Green Belt. Policy DM15 of the Council’s Development Management Policies confirms that proposals in the Green Belt should accord with the National Planning Policy Framework. Paragraph 14.48 of the Council’s Supplementary Planning Document: Residential Design Guidance 2016 (SPD) states that in respect of proposals in the Green Belt and as a guiding principle the volume of the original dwelling should not be increased by more than 25% by external measurement in order to protect openness. 8. Although the detailed calculations are not before me, and no information provided on the floorspace and volume of the original dwelling, the Council has indicated that the proposed pool development would result in an additional 25% floorspace to the existing dwelling house. The Council has further set out that the property already benefits from several extensions and that the current proposal would lead to the property exceeding the 25% increase outlined as a rule of thumb under the SPD. The Appellant has contested these figures but has not provided any alternative calculations. I recognise that the volume of the proposed extension would be sizeable but there is no evidence before me as to how this would relate to the size of the original dwelling. 9. Furthermore, I agree with the Council that a mathematical calculation is not, on its own, conclusive. In this instance, the main bulk of the development would be underneath the existing hard landscaped terrace, with the garden terrace to the rear of the terrace further lowered to provide some access, light and ventilation to the pool area through the introduction of windows to the rear retaining wall. There would therefore be very limited external manifestations of the built development, and most of the visual changes would be to the levels of the garden area. The actual impact on openness through additional built development would therefore, in my view, be very small. 10. Taking all of these factors together, it is my conclusion that the proposed development would not be inappropriate development for the purposes of the Framework and development plan policy. There is therefore no need for the development to be justified by special circumstances. Issue b) Character and Appearance 11. Section 72 (1) of The Planning (Listed Buildings and Conservation Areas) Act 1990 requires me to pay special attention to the desirability of preserving or enhancing the character or appearance of conservation areas. The designated heritage asset of the Mill Hill Conservation Area is an extensive area encompassing a number of large institutional buildings in their own grounds together with a wide range of residential uses including large houses in extensive grounds giving the whole Conservation Area a semi-rural and very low density spacious character in verdant and wooded surroundings. I am Appeal Decision APP/N5090//D/18/3210791 4 advised by the Appellant that the appeal property is also a non-designated heritage asset in that it is locally listed. 12. The development would be largely screened from general view both because of the form of the development at basement level and being at the rear of the property. There are a number of mature trees in the vicinity of the proposal. A number of reports have been submitted in relation to the protection of the trees during construction, but these date back to 2010 and are therefore now significantly out of date. Although I am generally satisfied from the information before me and my site visit that the existing trees would not be materially affected by the proposed works, I consider that updated information is required in respect of the trees and tree protection measures given the contribution that the trees make to the character and appearance of the existing site and to the Conservation Area. This is a matter that can be addressed by condition. 13. Given the form of the proposal and its siting, I do not consider that the proposal would have a material effect on and would therefore preserve the character and appearance of both the locally listed building and the Mill Hill Conservation Area. There would be no conflict with Policy DM06 of the DMP Policies or Section 16 of the Framework 2018, all of which seek a high standard of design which respects the local context, including designated and non- designated heritage assets. Other Considerations 14. The Appellant has drawn my attention to the several previous decisions granted by the Council for a similar form of development at the appeal property, including under Reference 14/07720/FUL. These are listed in the Officer’s report, but not commented upon. I have taken them into account but my decision is based on the planning merits of the proposal before me. Conditions and Conclusion 15. In terms of conditions, the materials as specified on the application forms should be adhered to in the interests of protecting the character and appearance of the existing property and of the Conservation Area, as well as a condition to list the approved plans for the avoidance of doubt and in the interests of proper planning. As the proposal relates to a private garden area, there would be no planning justification, in my view, to require further landscaping details. 16. As indicated above and although the application is accompanied by a range of reports relating to the protection of trees on the site, these are now significantly out of date and require in my view to be reviewed and updated. In order to be effective, it is my view that the condition relating to the protection of the existing trees requires to be a pre-commencement condition. In accordance with Section 100ZA (5) of the Town and Country Planning Act 1990 and The Town and Country Planning (Pre-Commencement Conditions) Regulations 2018, I have therefore requested and received the Appellant’s written agreement to the imposition of this condition. Appeal Decision APP/N5090//D/18/3210791 5 17. For the reasons given above and having regard to all other matters raised, including in representations, I conclude that the appeal should be allowed. L J Evans INSPECTOR