Appeal 3373025

The appeal is allowed and planning permission is granted for front facing mansard roof with 3 number round topped dormer windows and a side facing stair window at [site address] , Wandsworth, London [postcode] in accordance with the terms of the application, Reference 2025/1253 and the plans submitted with it, subject to the following conditions:

The development hereby permitted shall begin not later than 3 years from the date of this decision.

The development hereby permitted shall be carried out in accordance with the following approved plans: 001A, 010; 011; 020; 021.

The materials to be used in the construction of the external surfaces of the development hereby permitted shall match those used in the existing building.

Prior to the submission of this appeal, planning permission had been granted at the site for the erection of three dormer windows within the front roof slope1. This permission did not appear to have been implemented at the time of my site visit.

The main issue is the effect of the proposed development on the character and appearance of the host dwelling and the surrounding area, including whether it would preserve or enhance the character or appearance of the Wandsworth Common Conservation Area (CA). 1 Application Ref 2025/1201

The appeal property is one half of a semi-detached pair within a predominantly residential area. It is a well-preserved mid-19th-century villa. The adjoining dwelling, [address] (No. 29), has been altered by the addition of a front mansard roof, which is now an established component of the streetscape.

[address] is characterised by an eclectic mix of detached, semi-detached and terraced dwellings displaying a variety of scales, heights and architectural forms. Several properties incorporate dormers, mansards and other roof alterations that are visible from the public realm. This variety of roof forms, materials and detailing contribute to a visually rich and engaging streetscape, one defined by architectural diversity rather than uniformity.

The appeal site is also located in the CA. The terms of Section 72 of the Planning (Listed Buildings and Conservation Areas) Act 1990 require me to pay special attention to the desirability of preserving or enhancing the character or appearance of conservation areas.

The Wandsworth Common Conservation Area Appraisal (CAA) identifies Character Area H ([name]) as having the appearance of a village adjacent to the Common, notable for its mix of richly detailed, individually designed houses and the visual interplay between the built form and open space. The significance of this part of the CA lies in its diversity of architectural expression and its fine-grained urban form. The area thereby has both architectural and historic interest. The appeal dwelling makes a modest contribution to the character and appearance of the CA, with the mansard at No.29 disrupting the original symmetry of the pair and diminishing their collective contribution to the streetscape.

The proposal would introduce a mansard roof across the front roof slope, containing three arched dormer windows. The design takes reference from the host dwelling’s architectural vocabulary, in particular, the arched window forms of the lower facade and proposes the use of traditional materials.

Taken in isolation, a front mansard of this scale could risk undermining the integrity of the original roof form. However, in this instance, the principal visual outcome would be the reinstatement of balance within the semi-detached pair. The proposal would diminish the visual dominance of the existing mansard at No. 29 and reinstate a degree of symmetry and compositional integrity to the pair, contributing positively to the rhythm of the street scene. The mansard would be set behind the existing projecting gable and side parapets ensuring these key elements in the architectural hierarchy of the roofscape remain clearly legible. Chimney stacks would also be retained.

The three dormers, by virtue of their modest proportions, sympathetic detailing, and rhythm across the roof plane, would effectively break down the perceived bulk of the mansard. In this respect, the design quality would represent a clear enhancement over the adjoining example and respond positively to the design and architecture of the host dwelling.

Roof variation and alterations, including dormers and mansard forms, are not uncommon along [address]. Their cumulative presence reflects a process of gradual architectural evolution that contributes to the street’s layered historic character. Against this backdrop, the proposal, where visible in oblique views, would not appear incongruous but would form a natural continuation of that established pattern. The proposal would thereby reinforce the prevailing local character and the area’s architectural diversity, which the CAA itself identifies as a defining feature of this part of the CA.

The Wandsworth Housing Supplementary Planning Document (2016) (the SPD) advises that in conservation areas, original building appearances should be preserved, and front mansard roofs are generally unacceptable where visible. In this case, the site’s specific circumstances and the absence of visual harm are material considerations that outweigh that guidance of the SPD.

Taking these factors together, the proposal would have a neutral effect on the significance of the CA, preserving its overall character and appearance. The alteration to the host dwelling would read as a proportionate response to its context, forming part of the area’s ongoing architectural evolution rather than representing an erosion of its heritage value.

Overall, I conclude that the proposal would not harm the character or appearance of the host dwelling or the surrounding area. It would also preserve the character and appearance of the CA as a whole and there would be no harm to its significance as a designated heritage asset. As such, the proposal would accord with Policies HC1 of the London Plan (2021) and Policies LP1, LP3 and LP5 of the Wandsworth Local Plan 2023-2038 (2023), which amongst other things, seek to protect heritage assets and deliver design that protects the character of existing buildings. For the same reasons, the proposal accords with section 16 of the National Planning Policy Framework (2024) (the Framework) relating to conserving the historic environment.

[address] (No.26) is an early 19th [name] listed building, valued for its architectural detailing, materials, and contribution to the historic character of the area. Its setting comprises the immediate curtilage and surrounding residential plots within the street scene.

While the appeal site lies within the wider setting, it is separated from the listed building by distance, other dwellings and boundaries, such that it makes only a limited contribution to its significance. The proposed development, by virtue of its location, scale and siting, would not intrude upon or diminish the elements of the setting that contribute to that significance. I find that the proposal would preserve the significance of No.26, causing no harm to its architectural or historic interest.

I have considered the conditions suggested by the Council against the tests of paragraph 57 of the Framework and advice in the Planning Practice Guidance. In addition to the statutory time limit condition, I agree that a condition specifying the relevant plans is necessary to provide certainty. A condition relating to materials is also reasonable and necessary in the interests of safeguarding the character and appearance of the area.

A condition requiring obscure glazing to the side-facing window is unnecessary, as the window would serve only a stairwell and would not give rise to any material loss of privacy. Furthermore, the limited fenestration within the flank elevation of the adjoining property ensures that no overlooking or perception of overlooking would occur.

For the reasons given above, having taken account of the development plan as a whole, along with all other relevant material considerations, the appeal should be allowed.