Two storey side and rear extension with new dormers and fenestration changes

Appeal Decision Site visit made on 17 June 2025 by O Marigold BSc DipTP MRTPI an Inspector appointed by the Secretary of State Decision date: 09 July 2025 Appeal Ref: 6000203 29 Hertford Avenue, East Sheen, Richmond Upon Thames, London SW14 8EF • 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 Robert Logan against the decision of the Council of the London Borough of Richmond Upon Thames. • The application Ref is 25/0187/HOT. • The development proposed is two storey side and rear extension with new dormers and fenestration changes. Decision 1. The appeal is dismissed. Main Issues 2. The main issues are the effect of the proposal on (1) the character and appearance of the area, and (2) flood risk. Reasons Character and Appearance 3. The site consists of a two-storey detached dwelling. It lies within a street of suburban houses with a wide variety of designs and a strong Arts and Crafts influence. The proposal includes replacing an existing single-storey rear extension with one of two stories. Also proposed are new dormers to the front and rear, and extensive elevational changes, such as the use of timber framing and a front gabled feature. However, the main structural elements, roof and walls of the existing dwelling would be retained. 4. The Council’s House Extensions and External Alterations Supplementary Planning Document (SPD), adopted May 2015, advises that side and rear extensions should not dominate the existing house and should harmonise with its original appearance. It states that one way to achieve this, particularly for detached properties, is by integrating the extension with the house. 5. The proposed rear extension would have an integrated design that seeks to replicate the barn style and quad-pitch roofline of the original house. It would not obscure any notable existing views, and would increase the size of the existing building by around a third. 6. Even so, because of its overall height, length and bulk, the rear extension would have a large mass and scale. It would extend two-storey development deep into the rear garden, with a ridgeline only very slightly below that of the existing Appeal Decision 6000203 2 dwelling. Consequently, the rear extension would appear overly dominant and excessive, harming the appearance of the host property, including when viewed from Hertford Avenue. 7. Examples of other extensions nearby have been cited. Few of these appeared to have a design or form directly comparable to the proposal. Nor are the planning histories of these examples before me. In respect of extensions at 27 Hertford Avenue, I do not find the existence of what the appellant calls a ‘large and incongruous’ addition to be a convincing reason to justify further harm. 8. The proposal includes a new rear dormer, intended to balance the overall composition including the two-storey extension and another dormer. That said, in joining with the window below, it would have an incongruous vertical emphasis. This would disrupt the usual window hierarchy, where dormer windows are smaller than those below. In these respects, the proposal would conflict with the advice of the SPD. 9. As identified in the East Sheen Village Planning Guidance, adopted December 2015, key features of Hertford Avenue and the surrounding area include external materials of applied timbering, as part of the Arts and Crafts influence. However, the panelling proposed, being focused into solid areas of mass, would not reflect the style of timber framing of properties locally, where it is formed around open areas of render in a ‘mock-Tudor’ fashion. As such, this feature would appear incongruous. 10. For the reasons given above, the proposal would harm the character and appearance of the area. It would therefore conflict with Policy LP1 of the Council’s Local Plan, adopted July 2018, which requires development to have an acceptable form, scale and massing, and be assessed against the SPD. For the same reasons, it would conflict with the similar requirements of Policy 28 of the emerging Publication Local Plan, and with the National Planning Policy Framework which seeks development that is visually attractive and sympathetic to local character. Flood Risk 11. The proposal would increase built form and hard surfacing at the site. It is located within Flood Zone 1 but also within an area susceptible to elevated groundwater flooding. In such circumstances, Local Plan policy 21 makes clear that a Flood Risk Assessment (FRA) must be provided. No FRA was submitted during the application stage. 12. At appeal, the appellant has stated that the proposal would be minor in size, have floor levels no lower than existing, and that flood proofing will be incorporated ‘where appropriate’. However, I have few details of the potential for flood proofing here, or its effects on the proposal. This contrasts with 51 Hertford Avenue1, where some technical construction details were provided as part of an FRA. 13. Consequently, the information provided is not sufficiently detailed to show that acceptable flood proofing measures can be achieved. Nor can this matter be left to a planning condition, because the measures may necessitate alterations to the scheme. As a result, in the absence of substantive evidence to the contrary, I must conclude that the proposal would increase flood risk on the site or beyond. It would 1 LPA reference 24/3156/HOT Appeal Decision 6000203 3 therefore conflict with Local Plan policy 21 and the similar requirement of emerging Publication Plan policy 8. Other Matters 14. The proposal would improve the internal accommodation within the dwelling, resulting in a more efficient use of land. It would also result in environmental enhancements. However, as these benefits relate to just one dwelling, I give them limited positive weight, and they do not overcome the concerns that I have identified. Planning Balance and Conclusion 15. For the reasons given, I have found conflict with the Development Plan as a whole. The material considerations in this case, and the weight I give to them, do not indicate a decision other than in accordance with the Development Plan. This leads me to conclude that the appeal should be dismissed. O Marigold INSPECTOR