Loft conversion with rear dormer to accommodate an additional bedroom and en-suite

Appeal Decision Site visit made on 25 February 2026 by E Everitt BA (Hons) MSc MRTPI an Inspector appointed by the Secretary of State Decision date: 20 March 2026 Appeal Ref: 6002070 135 Cotterill Road, Tolworth, Kingston Upon Thames KT6 7UJ • 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 Luke & Philippa Beetlestone & Franklin against the decision of the Council of the Royal Borough of Kingston Upon Thames. • The application Ref is 25/02042/HOU. • The development proposed is loft conversion with rear dormer to accommodate an additional bedroom and en-suite. Decision 1. The appeal is dismissed. Preliminary Matter 2. Within their appeal submission, the appellant provided an assessment of the impact of the proposed development on the sunlight reaching 133 Cotterill Road. The main parties have been given the opportunity to provide comments on this assessment. I have had regard to the comments received and have considered the proposal in light of the submitted assessment. Main Issues 3. The main issues are: • the effect of the proposed development on the character and appearance of the host building and surrounding area; and • the effect of the proposed development on the solar panel on the roof of No 133. Reasons Character and appearance 4. The appeal property is an end-of-terrace dwelling located within an area characterised by residential properties. A variety of architectural styles is present within the surrounding area and a number of properties have been altered from their historic forms, including through rear dormer extensions. Consequently, the surrounding built form appears varied with limited consistency in respect of the siting and size of buildings as well as colours, materials and design features. This is particularly the case when viewed from the rear. Despite this variation in the surrounding area, the terrace of which the appeal property forms part has a Appeal Decision 6002070 2 broadly uniform roofscape, with the roofs to the main buildings and rear outriggers having a simple pitched form. 5. The proposed rear dormer would extend across the majority of the main roof of the appeal property and part of the roof of the outrigger. The dormer would be set down from the ridge height, set off from the flank elevation and set back from the eaves. Nevertheless, as a result of its projection onto the outrigger, it would appear as a bulky, dominant and overwhelming addition to the appeal property. 6. Moreover, notwithstanding that it would be clad in tiles matching the existing roof, the proposed dormer would appear at odds with the host building by reason of its contemporary design which would contrast starkly with the traditional design of the existing building. In this regard, whilst its design may respond to the geometry of the outrigger, the dormer would appear incongruous in the context of the existing built form of the dwelling and the terrace of which it forms part. 7. I acknowledge that there would be limited visibility of the proposed dormer by reason of its siting to the rear of the property. I also accept that it would be viewed in the context of the varied built form visible to the rear of the property, including some examples of existing rear dormers. Nevertheless, the existing rear dormers in the vicinity of the appeal site are not dominant features of the area. Additionally, they are predominantly confined to the main roofs of properties, appearing subservient due to their siting and scale. In contrast, by reason of its projection onto the outrigger, the appeal proposal would appear unduly prominent and incongruous. In this context, the presence of nearby rear dormers does not, ultimately, lessen the harm that the appeal proposal would result in. 8. The appellant has drawn 3 appeal decisions to my attention at 79 Mayfair Avenue, Worcester Park, 33 Merritt Gardens and 54 Amberwood Rise1. I do not have full details of these cases, or plans showing the proposals, before me. Nevertheless, it is evident that the cases differ from the appeal case in several respects. For example, the dormers proposed at 79 Mayfair Avenue, Worcester Park and 33 Merritt Gardens were located on the main roof slope of the properties whereas the appeal proposal would also extend onto the rear outrigger. Moreover, in the former case, the dormer was considered to be appropriately scaled in relation to the remainder of the dwelling. Similarly, in the latter case, the dormer was found not to appear overly dominant or as a disproportionate addition to the main dwelling. In contrast, for the reasons set out above, the appeal proposal would represent a bulky, dominant and overwhelming addition to the appeal property. 9. In the case of 54 Amberwood Rise, the dormer was found to have a rebalancing effect on the terrace, taking into account an existing roof extension of broadly the same design at the other end of the terrace. As such, the context within which the proposal was considered differed substantially to that of the appeal proposal, which would unbalance the existing broadly uniform roofscape of the terrace. Consequently, the conclusions reached in respect of these cases, which are also located elsewhere within the Borough, do not alter my findings in relation to the appeal scheme. 10. For these reasons, I conclude that the proposed development would have a harmful effect on the character and appearance of the host building and surrounding area. As such, the proposal is contrary to the relevant provisions of 1 APP/Z5630/D/25/3366503, APP/Z5630/D/22/3303318 and APP/Z5630/D/23/3314899 Formatted: Polish Appeal Decision 6002070 3 Policies CS8, DM10 and DM11 of the Royal Borough of Kingston Upon Thames Local Development Framework Core Strategy 2012 (the Core Strategy) and Policy D3 of the London Plan 2021 (the London Plan). These policies seek, among other things, development which relates well and connects to its surroundings, respects the prevailing development typology, scale, height, form and massing and enhances the local context. Effect on the solar panel on the roof of No 133 11. The proposed dormer would be located close to a solar panel on the roof of No 133. The Council raises concerns about the impact of the proposal on the performance of this solar panel due to overshadowing, in the context of McLennan, R (on the application of) v. Medway Council & Anor (2019) EWHC 1738 (Admin). 12. Within their appeal submission, the appellant has provided a Sunlight & Daylight Assessments Impact Assessment. This report concludes that the proposal would lead to a modest reduction in the Annual Probable Sunlight Hours (APSH) received by the solar panel at No 133. This retained value would be above the threshold of 0.85 identified in the Building Research Establishment’s BRE 209 guidance document (2022), below which a more detailed calculation of the loss of solar radiation is recommended to be undertaken. 13. I note the Council’s comments in respect of the limited detail provided within the submitted report, the inputs to the assessment and the presentation of an annual average figure only. However, there is no credible evidence before me that would lead me to conclude that requiring further assessment would be justified in this case, given that the APSH retained value would exceed the threshold for more detailed assessment set out in BRE 209. 14. Accordingly, I conclude that the proposed development would not have a harmful effect on the solar panel on the roof of No 133. As such, the proposal accords with the relevant provisions of Policy D3 of the London Plan. Among other things, this policy seeks development which aims for high sustainability standards. Other Matters 15. The appellant has put to me that the appeal property is unusually restricted, compared to neighbouring properties, in that it does not benefit from Permitted Development (PD) rights relating to rear dormer extensions. Nevertheless, I am assessing the proposal before me and have reasoned above why I have identified harm arising from it. 16. My attention is drawn to comparative improvements made as part of the appeal proposal relative to a previous planning application at the property. Nonetheless, I must make my decision on the basis of what is before me not the respective merits of any alternative scheme. 17. I acknowledge that no concerns are raised by the Council in respect of the extension of the property in principle, the proposed front rooflight or the effect of the proposal on the living conditions of occupiers of neighbouring properties with regard to light, outlook or privacy. Nevertheless, these matters do not lessen the harm I have identified above. As such, they do not lead me to an alternative conclusion on the first main issue. Appeal Decision 6002070 4 18. The absence of objections from neighbours or other third parties does not render the scheme acceptable and is a neutral factor in my decision. 19. I acknowledge that the proposal would provide additional internal space to support family living. I have had due regard to the Public Sector Equality Duty contained in section 149 of the Equality Act 2010 and appreciate that in dismissing the appeal individuals would be unable to derive the benefits associated with the proposal, having the potential to disproportionately affect them. However, it has not been demonstrated that the proposal before me is the only way in which the desired benefits could be achieved. Planning Balance and Conclusion 20. The proposed development would provide benefits for the appellant in terms of their living accommodation. However, I do not consider that these personal circumstances outweigh the harm I have identified from the proposal. 21. In conclusion, therefore, the proposal conflicts with the development plan and the material considerations do not indicate that the appeal should be decided other than in accordance with it. Consequently, I conclude that the appeal should be dismissed. E Everitt INSPECTOR