Appeal 3372676

The appeal is dismissed.

The site visit was undertaken by a representative of the Inspector whose recommendation is set out below and to which the Inspector has had regard before deciding the appeal.

The description of development above is as entered on the appeal form, as the appellant has indicated that it has changed from that stated originally on the application form in order to more accurately reflect the proposal.

The statutory duty set out in Section 72 of the Planning (Listed Buildings and Conservation Areas) Act 1990 (the Act) requires special attention to be paid to the desirability of preserving or enhancing the character or appearance of a Conservation Area.

The main issue is the effect of the proposed development on the character and appearance of the host dwelling and area, including whether it would preserve or enhance the character or appearance of the Cheyne Conservation Area (the CA).

The appeal property is a three-storey plus lower ground floor dwelling which forms one end of a short residential terrace. In as far as it relates to this appeal, the significance of the CA, within which the site is located, derives from its formal uniform Victorian terraces possessing of corresponding traditional features. A key element of this heritage significance is the buildings’ original butterfly roof form, notwithstanding that these are often hidden from public view behind parapet walls to front and side elevations. The Cheyne Conservation Area Appraisal (the CCAA) states that these valley roofs have become rarer and therefore are particularly valuable where they remain and includes a photograph of the appeal site’s butterfly shape to its rear, as is seen from the road. [name] recognise that the adjoining dwelling has been altered to a flat roof, this is one of the few properties across [address] that does not retain its historic roof profile.

The appeal dwelling is constructed in stucco and brick in common with the prevailing materials in the locality. Although there are some aesthetic differences across each house within the terrace of which it is a part, these variations do not undermine the strong regularity of its essential design and height, such that all have a similar appearance. My observation of this harmonious character included on approach from [address] to the west, this being a view highlighted in the CCAA, from which the terrace’s consistent three storey scale and chimney stack heights are apparent. This prevailing uniformity is furthermore characteristic of surrounding terraces within this part of the CA, and I agree with the CCAA in its identification of the appeal site together with the entirety of [address] as buildings that positively contribute to its significance.

Despite its positioning back from the street-facing parapet walls and the retention of the rearmost part of the existing roof, the proposed mansard roof addition would result in the substantial loss of the property’s valuable distinctive original valley roof form. In doing so, it would introduce a feature at the top of the building that would fail to respect, and harmfully contrast with, the appearance of both the host property and wider terrace. The mansard’s height, in combination with the associated raising of the existing chimney stacks, would also extend well above the existing parapet wall. As a result, even though it would be recessed from the edges of the building’s roof, the additional storey would be plainly discordant to the rhythmical vertical scale of the existing building as a whole.

The CCAA states that whilst the CA is generally in very good condition, the harmful alteration of rooflines through the addition of mansards in arbitrary designs has failed to preserve the unity of the groups of houses as is therefore a negative element. By paying scant regard to the basic uniformity of terrace’s height and traditional roofscape, the proposal would constitute the type of contextually incongruous negative feature that the CCAA seeks to avoid.

I appreciate that the proposal would be of limited visibility from street level within [address] and that it would not directly disturb the building’s parapet roof line, however this does in itself justify design that fails to reflect local distinctiveness. In any event, its awkward projection behind and above the parapet wall would still be partially evident in certain views from this street scene, in particular during months of the year when the site’s frontage trees are not in leaf. In addition, the scheme’s protruding bulk would be noticeable to a greater extent from adjacent [address], from which the raised chimney upstand and mansard would collectively appear as a conspicuously jarring mass atop one end of the terrace. Moreover, conservation areas are to be experienced from both the public and the private realm, and in this regard, there would be views of the proposed addition from the upper floors of many neighbouring properties.

I note that the proposal would retain the roof’s valley shape as expressed to the rear, that the mansard would be subservient in some respects and constructed of suitable materials, and that its dormer window has been centrally positioned between those windows below. These elements of the design do not however outweigh the harm identified above. By virtue of its unsympathetic scale and design to the form and character of the existing dwelling and locality, I find that the proposal would fail to preserve the character and appearance of the CA, thereby harming its significance as a designated heritage asset.

It is acknowledged that the National Planning Policy Framework (the Framework) supports the use of airspace above existing residential premises, including for mansard roofs where the development would be consistent with the prevailing form of neighbouring properties and the overall street scene. In this case, there are no mansards within the existing terrace, and such features are also not characteristic of [address] more broadly. Through its appearance and scale and the partial loss of the historic butterfly roof, the proposal would be at odds with the dominant character of the street scene. Accordingly, I find that this provision within the Framework does not provide support for the proposal.

The appellant has drawn attention to what it describes as a fall-back position having been established through the permitted development (PD) process. Specifically, details have been provided of a scheme that would lead to the loss of the butterfly profile across the whole roof through its replacement with a flat roof with rooflights1, whereas the appeal proposal retains its rearmost section. In both scenarios, the characteristic valley shape on the rear elevation would be retained.

The Courts have held that in considering the concept of a fall-back development as a material consideration, there should be a “real prospect” of it being implemented, and not just a theoretical possibility that the development might take place. It is also held that it is for the decision-maker to exercise their planning judgement on this matter and to ascribe the appropriate weight.

The PD scheme would not involve the extension of the roof to form an additional storey and would not therefore provide the additional bedroom and ensuite to be created through the appeal proposal. It is therefore not of a similar nature and consequently would not give rise to a comparable level of harm, which as identified above, principally arises from the mansard enlargement. Furthermore, given that the rooflights would serve a bedroom with an existing window, the PD scheme would ostensibly result in minimal benefits and so this lessens the likelihood that it would be delivered in any event. For these reasons, I have attached only very limited weight to the fall-back position as a material consideration.

The Framework stipulates that when considering the impact of development on the significance of designated heritage assets, great weight should be given to the asset’s conservation. Taking into account its scale and localised effect in the context of the extent of the CA, I find the harm that would arise from the proposal would be at the lower end of less than substantial having regard to the Framework, but nevertheless of considerable importance and weight in the planning balance of the appeal. Paragraph 215 of the Framework requires that less than substantial harm should be weighed against the public benefits of the proposal.

I acknowledge that the additional accommodation would be a desirable benefit of the scheme for the occupiers of the property. However, this would be of private benefit to the appellant and would not offer wider public benefits. Given the limited scale of the works, there would be some, albeit small economic benefits associated with the construction process. Accordingly, the public benefits of the scheme would 1 Council’s reference: CL/25/04737 be only minor and do not outweigh the harm identified to the significance of the designated heritage asset, and the great weight to be given to its conservation.

For the above reasons, I conclude that the proposal would have a harmful effect on the character and appearance of the host dwelling and area, including the Cheyne Conservation Area. As such, it would fail to satisfy the requirements of the Act and would conflict with Policies CD1, CD2 and CD12 of the Royal Borough of Kensington and Chelsea New Local Plan Review, July 2024 (LP). These policies require, amongst other things, that development is of a high standard of design including by respecting context and character and appearance, including historic characteristics, and with specific regard to roof alterations and additional storeys, that proposals be sympathetic to the form and character of the building or group of buildings. In addition, the proposal would conflict with [name] CD4 and CD15, which state that development is required to preserve or enhance the character or appearance and significance of the conservation area and to preserve or enhance views identified in conservation area appraisals.

The appellant has provided details of three other properties within the Council’s jurisdiction where mansard extensions have been approved. Though other examples of similar schemes can be a factor in determining the compatibility of a proposal with an area’s character and context, each case must be considered on its own merits based on the specific circumstances at each site. These circumstances will rarely, if ever, be identical.

A mansard scheme at [address] was approved by the Council in 20252. The context to that site is however dissimilar to the one before me, as the Council’s delegated report sets out that the majority of houses within the grouping concerned no longer retained their original butterfly roof, with a variety of consented alterations and additions built out to the roofs. The Council exercised its planning judgement in granting permission in this specific situation, which markedly differs from the prevailing original uniformity that characterises [address]’ roofscape.

My attention has been drawn to extensions at 22 Bonchurch Road3 and 18 Gordon Place4 allowed upon appeal in 2021 and 2024 respectively. In both cases, the Inspectors noted the presence or approval of multiple surrounding mansards and dormers as providing context for the respective schemes. Although, like the appeal proposal, [address] formed one end of a terrace with an unbroken roof line, the Inspector observed that due to its location and orientation, the dwelling reads more so as part of [address], a street scene in which roof extensions are commonplace. In contrast, the evidence before me and my own observations on site lead me to conclude that extensions or alterations to the original roof form are rare exceptions to the prevailing historic butterfly profile on both the terrace of which the appeal property is a part, and the adjacent terrace to its east.

Consequently, these examples do not lead me to a different conclusion on the main issue in this appeal. 2 Council’s reference: PP/25/00066 3 Appeal reference: APP/K5600/W/21/3279674 4 Appeal reference: APP/K5600/D/24/3337082

The proposal conflicts with the development plan and there are no material considerations, including the fall-back position, to which I attribute very limited weight, which indicate that permission should be granted. For the reasons given above and having had regard to all other matters raised, I recommend that the appeal be dismissed.

I have considered all the submitted evidence and my representative’s report and on that basis the appeal is dismissed.