Appeal 3344942

The appeal is allowed and planning permission is granted for the erection of a rear mansard roof extension and the installation of two roof lights to the front roof slope at [site address] in accordance with the terms of the application, Ref 23/04065/FUL, 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: A-P-012, A-P-013, A-P-014, A-P-015, A-P- 016, A-P-017 and A-P-018

The rooflights to the front roof slope of the development hereby permitted will be set flush with the roof and have a black frame.

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

Subsequent to the decision made by the Council on the planning application to which this appeal relates, the National Planning Policy Framework was revised. I have therefore made my decision with regard to the National Planning Policy Framework (December 2024) (the Framework).

As the description of development varies in documents submitted, I have used that of the Council’s decision notice, as this is a full and accurate description that has also been used by the appellant for their statement.

The main issue is the effect on the character and appearance of the appeal dwelling and that of the local area, with reference to The Chase Conservation Area (the CA)

The appeal dwelling is a three storey plus basement semi-detached house. It is located on a street, which in this part, is made up of similar generously proportioned Victorian semi-detached houses with shared Dutch feature gable. These sit at the centre of the CA, a small CA that includes houses on either side of the street.

The significance of the CA rests in it originally being a driveway from [address] to [name], which was later developed as a residential street in the late 19th century, in a variety of different architectural styles that creates a diversity of character. In this regard the appeal dwelling makes a positive contribution to the significance of the CA.

In line with the duty imposed on me by section 72(1) of the Planning (Listed Buildings and Conservation Areas) Act 1990, I have given considerable importance and weight to the desirability of preserving or enhancing the character or appearance of the CA.

The proposed rear mansard extension with two rear dormer windows would be set slightly below the existing roof ridge tile, with a front roof slope at 70 degrees. The proposed mansard would be slate clad to match the existing roof, and the proposed dormers would be lead clad with traditional window detailing to match existing. The proposal also includes the enlargement to the rear part of the existing flank gable and party wall with its semi-detached pair to accommodate this mansard roof form.

Two small roof lights are proposed for the front roof slope, although it is not clear from the submitted drawings whether these would be set flush into the roof with a black frame and would accord with the guidance set out in the [name] 4 (2023) (the LDG). However, to ensure that they reflect the design of the appeal dwelling and the character and appearance of the streetscape, the detailed design of these can be made the subject of a suitably worded condition.

The Council officer’s report makes mention of the proposed interior floor to ceiling heights being 2 metres rather than 2.1 metres set out in the LDG. Although it is not clear to me from where the where the Council have obtained this measurement, where the external maximum height given for the proposed mansard is 2.44 metres. However, the Council’s decision notice does not include the proposal not being habitable as a reason for refusal, and as I find that from the submitted drawings the proposal would appear to be in excess of 2m in height over more than 50% of the proposed floor area of the proposal, it would create habitable space.

The proposal includes a transition point of approximately 2.4 metres high between the 70 degree front slope and the flat roof of the mansard. The LDG recommends that this should be 2.3 metres if all the mansards in a row are to link up. However, there is currently no mansard on the appeal dwellings semi-detached pair for it to match to, and a future proposal for a mansard on this property can be designed to match the proposed 2.4 metre transition point.

The LDG also recommends that the sill level of dormer windows should be a minimum of 1 metre above floor level and the proposal is for a dormer sill of approximately 0.65 metres. However, submitted drawings indicate traditionally formed dormer windows that reflects the proportions and design of the existing fenestration of the appeal dwelling.

Whilst the proposal does not accord with the LDG in terms of the exact dimensions given for the 70 degree to flat roof transition and sill levels for dormer windows, this is guidance to be applied with regard to individual context and circumstances. In this regard, I find that the scale, massing, proportions and detailed design of both the proposed traditionally designed rear mansard with dormers would result in a subordinate addition to the appeal dwelling that would respect its architectural integrity and that it would not, therefore appear as an incongruous addition.

The LDG further states that rear mansards on double pitched roofs would generally not be considered appropriate in conservation areas. However, there are a substantial number of similar extensions that appear to be of varying age to properties in the street, including to the neighbouring house at 55 The Chase. These rear mansard extensions form part of the existing roofscape that appear to complement their host properties as traditionally designed additions and these appear to provide a reasonable design exemplar for the proposal, which would allow it to blend into the existing streetscape in views of the rear of properties on this side of the street. As such, I find that the proposal would not be detrimental to the significance of the CA and would preserve its character and appearance.

Other interested parties have raised concerns with regard to the effect of the construction phase of the proposal on the occupiers of neighbouring properties. These are substantially covered by other legislation and the scale of the proposal would not justify unnecessary restrictive conditions on an approval beyond what this legislation allows for.

For these reasons, I find that the proposal would result in no harm to the character and appearance of the appeal dwelling and would preserve that of the CA. As such, it would accord with Policies Q2, Q5, Q8, Q11 and Q22 of the Lambeth Local Plan (2021). Collectively, these seek to ensure that development, including extension, is of high design quality, visually attractive, does not compromise visual amenity from adjoining sites and the public realm, sustains local distinctiveness and preserve or enhances the character or appearance of conservation areas.

Along with the standard condition relating to the timing of implementation, I have attached conditions to ensure design quality that require compliance with the approved drawings, materials that match existing and the flush setting in and dark colour of the proposed front roof lights.

For the reasons given, the appeal is allowed.