Double storey side extension to replace existing single storey side extension, small rear infill extension, reconfiguration of ground and first floor to provide better layout

Appeal Decision Site visit made on 29 July 2026 by J Bell-Williamson MA MRTPI an Inspector appointed by the Secretary of State Decision date:08 September 2026 Appeal Ref: 6010603 17 Lyndon Mead, Sandridge, Hertfordshire AL4 9EX • 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 Connor Robertson against the decision of St Albans City & District Council. • The application Ref is 5/25/2222. • The development proposed is double storey side extension to replace existing single storey side extension, small rear infill extension, reconfiguration of ground and first floor to provide better layout. Decision 1. The appeal is allowed and planning permission is granted for double storey side extension to replace existing single storey side extension, small rear infill extension, reconfiguration of ground and first floor to provide better layout at 17 Lyndon Mead, Sandridge, Hertfordshire AL4 9EX. The permission is granted in accordance with the terms of the application Ref 5/25/2222, dated 5 December 2025, subject to the following conditions: 1) The development hereby permitted shall begin not later than three years from the date of this decision. 2) The development hereby permitted shall be carried out in accordance with the following approved drawings, all with the prefix 250021-PL-D: 0001 Rev P3 (block plan), 0002a Rev P3 (ground floor), 0003 Rev P3 (first floor), 0005 Rev P3 (roof), 0007 Rev P3 (section), 0008 Rev P3 (front elevation), 0009 Rev P3 (rear elevation), 0010 Rev P3 (side elevation) and 0011 Rev P3 (side elevation). 3) The materials to be used in the construction of the external surfaces of the extensions hereby permitted shall match those used in the existing building. 4) The two upper floor windows in the elevation facing Lyndon Mead shall be fitted with obscured glass and have fixed frames to a height of 1.7 metres above the floor of the room in which each window is installed and shall be permanently retained in that condition. Appeal Decision 6010603 2 Preliminary Matters 2. A new version of the National Planning Policy Framework (the Framework) was published on 17 August 2026. The content of the revised Framework has been considered but in light of the facts in this case it does not alter my conclusion. 3. The appellant responded to the Council’s first reason for refusal by providing a set of revised plans as part of the appeal submissions, with a reduced red line area excluding the amenity land outside No 17’s curtilage. A revised plan was also submitted with the appeal showing an increase in size of the upper floor windows to the extension’s side elevation facing Lyndon Mead1. 4. The Council has been consulted on these revised plans and indicates that the changes to the red line area overcome its first reason for refusal. It also comments that the change in window size would not raise any material planning concerns, subject to a condition requiring these to be fixed and obscure glazed below 1.7 metres from internal floor level, to protect neighbouring privacy. 5. The change to the red line area does not have any bearing on the proposed extension and does not otherwise result in any physical changes. As such, it does not involve a substantial difference or fundamental change to the application. Also, for the same reason, I consider that this change does not cause any unlawful procedural unfairness to anyone involved in the appeal2. Consequently, for this reason and the Council’s comments, I have taken account of the revised plans in determining the appeal and have not considered the first reason for refusal any further. 6. With regard to the revised window size and suggested condition, I note that one window would serve a bathroom, while the other would serve a bedroom with a dual aspect. On this basis, with the suggested condition in place, the revised window size would not be a substantial change and would not result in unfairness. I have, therefore, taken account of the revised plan. Main Issues 7. The main issues are: • whether the proposal would be inappropriate development in the Green Belt having regard to the Framework and relevant development plan policies; and • whether any harm by reason of inappropriateness would be clearly outweighed by other considerations, so as to amount to the very special circumstances required to justify the proposal. Reasons Whether the Proposal is Inappropriate Development 8. The appeal property is a two storey detached dwelling in a residential road of similar property types. The surrounding area is residential in character. 1 Ref 250021-PL-D 0010 Rev P3. 2 These substantive and procedural tests derive from the judgment in Holborn Studios Ltd v The Council of the London Borough of Hackney [2017] EWHC 2823 (Admin), which refined the established principles set out in Bernard Wheatcroft Ltd v SSE [JPL 1982 P37]. Appeal Decision 6010603 3 9. The Framework makes clear that development in the Green Belt is inappropriate unless it falls within one of the categories listed in policy GB7. With regard to an extension or alteration to an existing building, for development not to be inappropriate the Framework requires that the extension will not result in a disproportionate increase in size compared to the original building3. 10. The Council refers to Policies 1 and 13 of its District Local Plan Review 1994, and to Supplementary Planning Guidance, all of which concern development in the Green Belt. These policies and guidance considerably pre-date the Framework and with regard to extensions they require an assessment of scale, visual impact and effect on character. As such, they do not reflect the Framework’s approach to assessing whether or not a proposal is inappropriate development. 11. I note also that the Council has consulted recently on modifications to policies in its emerging local plan, which includes Policy LG9 to replace Policy 13 concerning extensions in the Green Belt. The principal changes to the policy result from the local plan Inspector’s recommendation that it should better reflect national policy in the Framework. Therefore, for these reasons, I consider that the more recent national policy should be the principal basis for assessing the proposal for the purposes of this issue. 12. The Council indicates that No 17’s original size in terms of floorspace was just under 149m2. Previous additions of just under 25m2 together with the proposed extension of just over 37m2 amount to a nearly 42% increase in floorspace above the size of the original dwelling, or an increase of 176m3 by volume. The appellant, however, disputes this and by their own calculation considers that the increase would be 39%. 13. The two storey extension would largely be positioned on the footprint of the existing single storey element to the side and it would be set down from the roof of the host dwelling and set back from the front elevation. Due to the lower height, set-back from the front and limited frontage width, the extension would not add substantive bulk or mass to the host dwelling. Moreover, the overall proportions of the dwelling would not be unbalanced as a result of the extension. 14. Taking these findings as a whole, the previous and proposed extensions result in a not insignificant change to the original building’s size in quantitative terms, whether the Council’s or appellant’s assessment is used. However, this must be balanced with the finding that the proposed extension would not alter the footprint or external dimensions of the dwelling to the extent that it would be disproportionate. 15. Therefore, on balance and for the reasons given, I find that the proposal would not result in a disproportionate addition over and above the size of the original building. Consequently, I conclude in accordance with the provisions of the Framework that the proposal would not be inappropriate development in the Green Belt. 16. Both parties refer to the effect of the proposal on the openness of the Green Belt. However, impact on openness is implicitly taken into account in the Framework’s exceptions unless there is a specific requirement to consider the actual effect on openness. Consequently, as it has been found that the proposal would not be 3 Policy GB7, 1b. Appeal Decision 6010603 4 inappropriate development, there is no requirement to assess the impact of the development on the openness of the Green Belt. Conclusion and Conditions 17. It has been found above that the proposal would not be inappropriate development in the Green Belt and so is not contrary to the Framework. Consequently, the appeal should succeed. 18. I have imposed the standard time condition and, to ensure the proper implementation of development in accordance with the submitted details, one requiring development to be carried out in accordance with the relevant plans, referred to above. 19. A condition requiring external materials to match those of the existing dwelling is also necessary in the interests of the character and appearance of the appeal property and surrounding area. Finally, a condition to require obscured glass in the new upper floor windows facing Lyndon Mead is necessary to maintain privacy, as referred to above. It is not necessary, however, to require the same for other new windows on the front and rear elevations as these are of similar depth and size to existing adjacent windows and will not affect privacy. J Bell-Williamson INSPECTOR