Appeal 6000389

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.

Prior to the consideration of this appeal, the Council adopted the Richmond upon Thames Local Plan (2025) (LP). The main parties were aware of what the emerging policies were at the time of the Council's decision, and they have not materially changed since their formal adoption. Therefore, I have had regard to the most up to date development plan.

The appellants have submitted an amended Flood Risk Assessment (FRA) with the appeal, which proposes a new surface water mitigation strategy. [name] appreciate that it was submitted in response to the Council’s comments on lack of information, the appeal process is not a means by which to evolve or amend a scheme. [name] is a significant change to the scheme and accepting it would prejudice the Council, technical consultees and other interested parties who have not had the opportunity to consider it. Therefore, I have not taken the amended FRA into account when making my recommendation.

The main issues of the appeal are the effect of the proposal on: • the character and appearance of the area; and • flood risk

[site address] is a unique property in terms of its layout, scale and historical context. Originally functioning as a coach house, as evidenced on an 1890 plan, it differs markedly from the surrounding residential form. Unlike the surrounding residential properties, the largely single storey [address] is positioned significantly further back from the highway, with a driveway separating it from the street.

The surrounding built form is varied, comprising three‐storey terraced properties with red brick, white render and mansard roofs. In addition to these, there are more traditionally designed semi‐detached dwellings opposite, and, further along, modern functional buildings and blocks of flats. Adjacent to the appeal site is a community fitness and swimming centre, which uses contemporary form and materials. There is therefore diversity of form and character in the area. In terms of residential properties, the distinctly different appearance of [site address] makes it an outlier within the street scene.

The proposed alterations, including the materials, increased ridge height, dormer additions and revised fenestration, would introduce a more contemporary appearance. Nevertheless, the scale of the dwelling would remain much smaller than the frontage houses. The differences in the two dormer designs would only readily be seen from the adjacent car park, and the use of glazing would limit the visual impact of these features. The cladding proposed would reflect the red tones of local brickwork and vertical emphasis characteristic of the traditional dwellings. Accordingly, the proposal would create a clear difference between the old and new parts of the building while retention of the original front rendered section and the single‐storey element would ensure that the building’s historic core remains legible.

Given the property’s existing distinctiveness and its limited visual relationship with the main street frontage, these changes would not appear discordant. The surrounding area already contains a mixture of traditional and modern development, and the proposal would sit within this broader pattern of architectural evolution. Consequently, in this context the increased scale and contemporary design proposed would not harmfully disrupt or erode the rhythm or character of the street scene or the existing dwelling. Taken as a whole, the scheme would not harm the character or appearance of the area and would sit comfortably within the varied architectural context of [site address] .

Consequently, the scheme accords with Policy 28 of the LP (2025), which, amongst other matters, requires that proposals are compatible with the local character and demonstrate a sympathetic upgrading and reuse of existing buildings.

The Council’s ‘[name] and External Alterations’ Supplementary Planning Document (SPD) (2015) provides general guidance for typical suburban house types. The appeal property does not share the characteristics of those dwellings, and therefore the relevance of the SPD is limited in this case.

The site is in a critical drainage area. The proposal would increase the roof area of the building, which has the potential to increase surface water run-off and increase flood risk on site or elsewhere. The site is also identified as being at high risk of groundwater flooding.

LP Policy 8 requires all developments to clearly demonstrate that they will avoid or reduce contributing to all sources of flooding, including surface water. It requires use of sustainable drainage systems (SuDS) in all development proposals and sets out a series of criteria to be met. These state that surface water should ideally be managed on site and schemes must demonstrate a reduction in surface water discharge to greenfield runoff rates wherever feasible. If that is not feasible, this must be justified and then schemes must achieve one of two criteria. [name] 12 and SI 13 of the London Plan (2021) take a similar approach, with SI 13 setting out a clear drainage hierarchy for dealing with surface water, with preference for green over grey features.

The evidence submitted with the application seeks to address surface water runoff and flood risk through changes in permeable surfacing. However, the information provided does not assess the greenfield runoff rate or set out why it cannot be met. Nor does it follow the criteria or drainage hierarchy required by policy. Moreover, it does not demonstrate how the measures proposed are appropriate in an area at high risk of groundwater flooding.

Consequently, there is insufficient information before me to demonstrate that the proposal would satisfactorily address surface water drainage, such that there would be no increase in flood risk on site or elsewhere. Nor has it been demonstrated that there is a technical solution available that could be secured by planning condition. Accordingly, the proposal would conflict with LP Policy 8, London Plan Policies SI 12 and SI 13 and the drainage provisions in the National Planning Policy Framework.

I have found that the proposal would have an acceptable effect on the character and appearance of the area. Whilst this weighs in favour of the scheme, it does not outweigh the unacceptable harm in respect of flood risk.

For the reasons given above and having had regard to all other matters raised, I recommend that the appeal should be dismissed.

I have considered all the submitted evidence and my representative’s report and agree with the reasoning and recommendation. On that basis the appeal is dismissed.