Appeal 3364479

The appeal is dismissed.

The main issues are: (i) the effect of the proposed development on the character and appearance of the Holland Park Conservation Area; (ii) the depth of proposed basement and whether its construction would adversely impact on the living conditions of neighbours; and (iii) the effect of the proposal on trees of amenity value.

The appeal property is a two-storey detached dwelling with rear garden located on the southern side of [address]. The property has a double-fronted frontage elevation with a closet wing component projecting from the rear elevation. Due to the heights of buildings and curvature of the road there is some mutual overlooking from the appeal property into adjacent rear gardens and vice versa.

The appeal site is located within the Holland Park Conservation Area (CA). The duty under Section 72 (1) of the Planning (Listed Buildings and Conservation Areas) Act 1990 (the Act) requires that special attention shall be paid to the desirability of preserving or enhancing the character or appearance of Conservation Areas. The Holland Park Conservation Area Appraisal 2017 (CAA) identifies the significance of the CA as deriving from the historic origins of [address] and the many examples of speculative mid-Victorian architecture that were built around it. [address] is identified in the CAA as forming part of this historic evolution albeit recognised as having more variation than in some parts of the CA due to later additions.

The appeal site’s contribution to the CA is that it is a largely unaltered villa building within a group (Nos 2-11) that were all designed by [name] in the 1850s. These buildings were originally built identically but many since have been changed over the years. For the most part, these changes have been well-integrated; the overall quality and appearance of buildings remain and can still be recognised as a distinct group. The appeal building itself retains original detailing, form, scale, gaps to neighbouring buildings and decorative features.

The proposal would add an in-line third storey to the existing building, with its top section remaining lower than its neighbouring properties at [address] and [address]. The additional storey’s scale and form would be similar to No 69, which is a good example of a successful in-line extension. Whilst it sits on the corner with [address], No 69 still forms a prominent part of [address]'s street scene and helps frame the context for the site more so than Nos 9 and 10 due to the curvature of the road. The building's original dentil cornice would also be retained, aligning with the approach taken on both its neighbouring properties. For these reasons, I find that the overall form and scale of the proposed in-line extension would be acceptable and not unduly harm the character of the building, subject to consideration of the detailed design of the proposal overall.

In terms of detailed design, the third floor would include three windows on its frontage elevation. [name] understand that the appellant has sought to respond to the Council’s pre-application advice, the proposed windows would appear markedly at odds with those on the floors below by being notably smaller as well as having different detailing on the brick work and frames. The effect of this would be the third-floor frontage appearing as visually discordant with the floors below in terms of window design. This would prominently and unacceptably detract from the appeal property’s aesthetic contribution both individually and as part of its group value to Nos 2-11, where the general consistency of windows in style and size across floors is a notable character feature of the area.

Furthermore, a notable characteristic of the street is that properties generally only have small and infrequent openings on their side elevations. The proposal would markedly contrast with this by proposing an increase of windows on its flank walls, particularly on the north east elevation. The new openings would also be disproportionately large and uncharacteristically located between the chimney stacks. Overall, the approach to new windows throughout lacks the required coherence and consistency in contrast with the pattern of openings on other properties along the street. This would harm the historic appearance of the building and how it appears as part of its group.

The proposed walk on rooflight would not accord with the Council’s Basements Supplementary Planning Document 2016 (SPD) by being located some distance from the dwelling. [name] agree that this would not have any impact on the street scene, it would be prominently visible from neighbouring and nearby properties when looking from their upper floor windows across into the appeal site’s garden area. Given its detached location and size, the rooflight would appear as an isolated and incongruous feature when lit at night that would be out of keeping with the generally understated appearance of rear gardens within the CA.

I note the appellant suggests that this visual impact could be mitigated for with additional landscaping and agreement of further details such as opaque glazing, disguised with grilles and / or making it smaller. I agree that there appears potential for one or more of these options to reduce the impact albeit there are no specific details before me that explain how effective these might be. These options need to be explored further before planning permission is granted.

The approach to limiting demolition, the inclusion of chimney stacks and the scale of the proportionate and subordinate side and rear extensions is acceptable as these aspects would respect the historic form and appearance of the building and maintain a suitable gap to the adjoining properties. The parapet to the top of the extension is intended to be rendered, which could be secured by a suitably worded condition. The acceptability of these aspects, however, do not justify the harm to the character and appearance of the CA identified.

To conclude and for the reasons stated, the proposal would neither preserve or enhance the character or appearance of the CA and would result in less than substantial harm to its special significance. Whilst this impact would be at the lower end of less than substantial harm, there are no public benefits identified that would outweigh this harm. The proposal, therefore, does not accord with Policies CD1, CD2, CD4, CD10, CD11, CD12 and CD13 of the New Local Plan Review 2024 (LP), which require development to respect existing context, character and appearance including historic characteristics, be locally distinctive, preserve or enhance the character or appearance and significance of the CA, and for roof alterations to be appropriately designed to make a positive contribution to townscape and the detailed design to be in character with the existing building. The proposal is also not consistent with the guidance contained in the Council’s SPD or the heritage provisions of Chapter 16 of the National Planning Policy Framework (the Framework).

Policy CD11 of the LP sets out the parameters for new basements, with criterion (b) stating that, other than for exceptions on large sites, basements must not comprise more than one storey. Policy CD11 is supported by guidance on basement design in the SPD. Paragraph 6.95 of the supporting text to Policy CD11 sets out that a single storey would generally be about 3 to 4 metres (m) from floor to ceiling height but with a small extra allowance for proposals with a swimming pool possible.

The garage and plant room would have a total depth of 4m, which is consistent with paragraph 6.95 and acceptable in terms of Policy CD11. The floor to ceiling height of the basement would be 3.3m with then the section with the pool adding a further 1.5m to give a total depth of 4.8m. There is additional space in the pool area to provide plant and ventilation that would add a further 0.65m to have a maximum depth of 5.45m. The appellant has provided numerous detailed examples that demonstrate single storey basements with pools with very similar dimensions have been granted planning permission by the Council elsewhere.

I am aware that the Council has referenced one recent example where a basement depth of around 5.45m was found to be excessive by a separate Inspector in appeal decision [name]/K5600/D/24/3339045. However, no details have been provided for this other scheme to be able to reasonably compare it with this appeal proposal.

Moreover, when looking specifically at the merits of this application, it appears to me that the proposal would not readily lend itself to be converted into two floors due to the way it would be laid out internally with just under half of the space clearly within the parameters set out in paragraph 6.95 and the remaining section slightly deeper to accommodate the pool. On balance and given the various examples of very similar proposals granted elsewhere I conclude that there is no substantive evidence before me that demonstrates the basement with the pool remaining in place would be used for anything other than the single storey that is proposed.

Reason for refusal 2 is also focused on the impacts from the proposed basement depth on neighbour’s living conditions arising from its construction. The appellant has provided compelling evidence, with reference to other developments in the area, to demonstrate the proposed construction duration would not be materially different to others approved by the Council. This could also be reasonably controlled by a Construction Management Plan type condition were the appeal acceptable in all respects. I am satisfied, therefore, that with conditions to control construction method, the proposal’s basement depth would be acceptable and would not result in adverse impacts on living conditions to the extent it would justify refusing planning permission. Accordingly, I find that the proposal accords with Policies CS9 and CS11 of the LP and the related guidance in the SPD.

There are various trees within the site, some of which are subject to a Tree Preservation Order. The planning application was supported by a detailed Arboricultural Impact Assessment (AIA). The AIA considered the impacts of the proposal on trees of amenity value, and suggested a series of mitigation measures, all of which appears to be reasonable. I note the Council, however, query whether the extent of existing root protection areas should be modified due to proximity to existing structures. As such, it would ordinarily be necessary to consider at this stage whether the Council’s concerns could be addressed through suitably worded conditions or not. However, as the appeal proposal is unacceptable for other reasons I do not need to consider this matter further in this decision.

For the reasons given above and considering all matters raised, I conclude that the proposal does not accord with the development plan in terms of its impact on the special character and appearance of the Holland Park Conservation Area and the appeal is dismissed.