Appeal 3364845

The appeal is dismissed.

An application for costs was made by [name] against the Council of the London Borough of Lambeth. This is the subject of a separate decision.

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

The appeal relates to a two-storey, end of terrace dwelling with a two-storey rear return and which occupies a corner location with a side return boundary to [address]. This south side of [address], and its hinterland, is residential in character comprising mostly late 19th and early 20th century properties. The dwelling’s entrance is roughly central to its side elevation. There is an existing single-storey lean-to addition along part of the rear return and adjacent to the entrance door. This links to a single-storey flat roof element that spans the remaining depth of the side elevation. A further lean-to extension with a staggered depth projects to the rear with a very shallow pitched roof and extends across and links with the internal space within the side addition.

The proposal would comprise two distinct elements. The ground floor side and rear extensions would be removed in favour of a single-storey flat roof extension which would project with a uniform depth of 3m beyond the building’s original footprint along the boundary with No 206, and which would wrap around the side elevation of the rear return, extending up to the plot’s opposing side boundary. The second element would comprise a rear mansard extension with an L-shaped element projecting over the rear return.

The appellant asserts that the proposed single-storey extension would merely replace an already substantial extension and with limited visual impact due to the topography of the area and screening by the existing 1.8m high side boundary fence. I disagree.

The existing extensions are rather ad-hoc appearing either lightweight and somewhat temporary in nature, or otherwise low level and largely out of sight from the public domain. The proposed extension would be significantly more imposing. The plans show that it would be built to a 3m height when measured from the land level closest to the dwelling’s entrance door. This height would run more or less aligned with the decorative brick band course which can be clearly seen on the flank elevation of the dwelling. Furthermore, the ground floor plan, [name] P01 REV-A, shows the extension’s flank wall running along the side boundary line of the site. The existing side extensions do not. They are set behind the site’s boundary fence and away from it, even if only by a small margin. Even if the fence were to remain, in my judgement, a significant part of the extension’s long side elevation would be seen from [address] at extreme proximity along the adjoining pavement.

The Lambeth Design Guide Part 4: Building Alterations, Extensions and Retrofit was adopted as a Supplementary Planning Document (SPD) in 2023. Where addressing single-storey extensions, including wrap-around additions, subordination is identified as key. Despite the lower levels of the appeal site relative to the adjoining road and pavement, the side/rear extension would be visible on the approach along [address] from its raised vantage points. By extending wider than the existing dwelling and along the back edge of the pavement, I share the Council’s view that it would fail to be seen as an appropriately subordinate addition.

My impression overall is that the single-storey extension would replace some moderately inharmonious additions but which nevertheless are reasonably inconspicuous, with a disproportionately deep and horizontally proportioned addition that would appear overly large and out of keeping with the size and proportions of the original building. Its large and unrelieved mass of brickwork set along the plot’s side boundary would be seen along the adjoining pavement and in views approaching from further afield as both dominant and visually overbearing.

Turning to the proposed roof extension. The SPD advises that on traditional properties with double pitched roofs a rear mansard is the best option in terms of optimising space and headroom without altering the street facing roof pitch. Notwithstanding, subordination is still identified as a key design objective. It further advises that where a rear roof extension projects over a rear return, an integrated approach should be adopted along with a rear mansard. In these circumstances SPD paragraphs 4.102 and 4.103 list a number of design criteria.

The proposed roof extension complies with some, but not all of the SPD’s design criteria. I do not share the appellant’s view that the breaches are all minor technicalities. For example, the flat top of the proposed mansard would be equivalent in height to the dwelling’s main ridge eliminating the opportunity for flashing and retention of existing ridge tiles; the plans appear to show fascia at the joins between the steep lower pitched roof of the mansard and its top roof rather than lead flashing; and no extended brick upstand walls appear to be proposed along the party wall with No 206. These omissions run counter to the SPD guidance. The circumstances at the appeal site do not suggest to me that the guidance should merely be set aside without reason. By failing to follow the SPD guidelines, the roof extension would be openly seen in a prominent corner position as a large, dominant, and poorly detailed addition that would be neither sub-ordinate nor properly integrated with the roof form of the existing dwelling.

Both individually and cumulatively, I find the proposed ground floor extension and roof extension to be unsympathetic additions that would be harmful to the character and appearance of No [address] scene. By failing to respond positively to the built form of the existing dwelling and its surroundings, the proposal would not display the quality of design required by Policies Q5 and Q11 of the Lambeth Local Plan 2020–2035, adopted in 2021. For the same reason there would be conflict with the National Planning Policy Framework’s objectives for achieving well-designed places.

The appellant has pointed to L-shaped roof extensions to other properties within the existing terrace of which No 208 forms part. However, none of these properties occupy a prominent corner location where the rear roof slopes are on clear view along the vista of an open street scene.

I am mindful that a roof extension could be constructed as permitted development and that this offers a legitimate fallback position with a real prospect of being implemented. However, such an addition would have limitations placed upon it in terms of volume increase. I have not been presented with any details to show any comparison with the appeal proposal, which is large and covers the majority parts of the dwelling’s rear roof slopes. I am therefore unable to conclude that any legitimate fallback position would have a similar degree of harm and that any differences would be only minor. As such, the weight I attach to the fallback position is only slight and insufficient to outweigh the harm that I have identified.

For the reasons given, the appeal is dismissed.