Appeal 3364909

The appeal is allowed and planning permission is granted for the erection of a mansard roof extension to provide second floor accommodation at [site address] , Lambeth, London [postcode] in accordance with the terms of the application, Ref 25/00454/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 approved plans: Site Location Plan at scale 1:1250 and [name] 22.01.100 Rev 02, 22.01.160 Rev 02, 22.01.200 Rev 07, 22.01.260 Rev 08 and 22.01.261 Rev 04.

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.

The main issue is the effect of the proposal upon the character and appearance of the appeal property and wider street scene.

The appeal property is a two-storey dwelling with a traditional London (butterfly) roof with two pitches aligned front to rear sloping into a central valley and concealed behind a front parapet. Together with its neighbour at No 173 it forms one half of a pair. No 173 is attached to a public house of markedly different appearance with a steep hipped roof and which in turn is attached to a terrace at Nos 167-143 (odd) where individual roof forms are hidden behind front parapets. The proposal is to add a mansard roof extension with dormers front and rear to create additional living accommodation at second floor level.

The Lambeth Design Guide Part 4: Building Alterations, Extensions and Retrofit was adopted as a Supplementary Planning Document (SPD) in 2023. The Council’s officer’s report quotes from SPD paragraph 4.99 which offers support in principle for roof extensions to optimise accommodation subject to subordination and protection of the building’s design integrity. Where dealing specifically with new mansards on traditional buildings, paragraph 4.106 of the guidance offers unequivocal support for the replacement of London roofs with a traditional full mansard except on heritage assets and buildings in conservation areas, subject to full accordance with ten set criteria. It is clear that changes to a dwelling’s appearance, roof profile and height are clearly accepted by the SPD as inevitable consequences, including where there are no adjoining historic examples, which is where the guiding criteria are intended to apply, as is the case at No 175.

The appeal property is neither a heritage asset nor located within a conservation area. The proposed mansard addition would be traditional in form, set back front and rear with the front parapet retained, appropriate materials, raised party walls and modest dormers evenly spaced and restricted in size to the lower roof pitch. There would be some deviation from the SPD criteria on two counts. The upper roof would be pitched at 15 degrees rather than the 30 degrees required by the guidance and, as an end property, no half-hip is proposed for the new roof. However, I share the appellants’ view that the shallow pitch would successfully reduce the proposed roof’s mass appropriate to the modest proportions of the dwelling whilst maintaining a traditional mansard form. By so doing, the omission of the hip-end and the building up of the flank wall over the height of the lower slope, would not, in my judgement, result in an overly dominant addition. As such, the SPD’s objectives for the approach to be taken for a new mansard on a traditional building would be met.

The Council has described a well-defined roof line for the terrace when looking south and an appreciation of their strong parapets. However, the appeal property is not directly an associated part of the terrace and in any event, I observed for myself a distinct lack of uniformity and regimentation to the appearance of the terrace in this regard. The parapets vary in detail, height, and alignment, as do the details of the dwelling’s elevations themselves. In addition, the roof profile of the terrace is already broken by the abrupt change at one end that is introduced by the attached public house. Further still, they sit within a wider street scene which displays other alternative pitched roof forms, including some with obvious accommodation at second floor level with forward facing dormers.

When all of this is considered, as an appropriately subordinate and sympathetic change that would retain the architectural integrity of No 175, I am not persuaded that there would be any significant impact from the proposal upon the wider character or appearance of the street scene that would be harmful. Overall, I am satisfied that the proposed roof extension would respond positively to the built form of the existing dwelling and its surroundings and as such would display the quality of design required by Policies Q5, Q8 and Q11 of the Lambeth Local Plan 2020– 2035, adopted in 2021.

In the event of the appeal succeeding, the Council has suggested three conditions. In addition to the standard time limit condition, a condition requiring the development to be carried out in accordance with the approved plans is necessary for the avoidance of doubt and in the interests of proper planning. I agree that a condition is also necessary to ensure that the development is carried out in materials to match the existing, in order to safeguard the character and appearance of the area.

For the reasons given above, the appeal is allowed.