Appeal 3303747

The appeal is dismissed.

There was a discrepancy between the floor plan and elevation plan submitted with the application with the depth of the rear extension being 7.2m on the elevation but 6m on the floor plan. The appellant has confirmed that this was an error and has submitted a corrected elevation plan with the appeal to align with the floor plan. As the floor plan clearly annotated the depth at 6m, I am satisfied that no party has been prejudiced by the correction of the elevation plan in the appeal process.

The main issues are: • The effect of the proposal on the character and appearance of the surrounding area; • The effect of the proposal on the living conditions of the occupiers of No 39 and [address] with particular reference to outlook and light; and • Whether the proposed development would be likely to increase the likelihood of flooding in the area.

The appeal property is a two-storey semi-detached dwelling on a street containing a mix of bungalows, two storey, detached and semi-detached properties. Many have been extended already but others haven’t.

Along this part of the western side of the street there are small gaps between the pairs of semi-detached dwellings. Some of the gaps have already been eroded by two storey side extensions, such as that at the neighbouring property (No 43) which extends to the common boundary. The pairs of semi-detached dwellings do not follow a strict building line. Instead, they are stepped back progressively when moving north along the road. As such, gaps between pairs of properties are particularly important as the perception of space between the pairs is not easily distinguished when travelling along the street due to the stepped building line.

The proposed side extension would be forward of the front façade of No 43. As such, even with a 1m gap at the first floor, due to the forward positioning of the host dwelling, the proposal would appear very tight in relation to No 43. In this regard, the proposal would appear cramped in the street scene.

The rear extension would be single storey with a flat roof and a small lantern. As such, it would be subservient in height to the host dwelling. Moreover, whilst it would obscure all of the original ground floor of the host dwelling, the first floor and roof structure of the original property would remain entirely visible.

It would project would to the rear considerably, significantly increasing the ground floor area of the host dwelling. However, the appeal property has a particularly long rear garden, and, in this regard, overall, it would not appear a disproportionate addition to the rear. It would have matching materials and the extensive use of glazing on the ground floor would be compatible with the host dwelling. My findings, on the rear extension, however, do not overcome my concerns regarding the side extension.

I therefore find that the proposal would have a harmful effect on the character and appearance of the surrounding area. The proposal would therefore conflict with the requirements of Policies BE1 and HE1 of the Hillingdon Local Plan: [name] - [name] (2012) (LP1), Policies DMHB1, DMHB5, DMHB11, DMHB12 and DMHD1 of the Hillingdon Local Plan: [name] - Development Management Policies (2020) (LP2), Policy D3 of the London Plan (2021) and the National Planning Policy Framework (2021) (the Framework), insofar as they are relevant to this main issue. These require, amongst other things, that all development, including extensions be designed to the highest standards and, incorporate principles of good design including harmonising with the local context.

The neighbouring property at No 43 has a small side bedroom window which would face the proposed first floor extension. The Council has not referred me to any local definition of a habitable room. However, the London Plan (2021) defines a habitable room in its Glossary as any room used or intended to be used for sleeping, cooking, living or eating purposes. In this regard, the bedroom would constitute a habitable room.

The appellant advises that the side window is a secondary window, with the front much larger window providing the main outlook and light into the room. However, the Council dispute this, and advise that a partition wall has been installed creating a bedroom with the side window being the only source of light and outlook serving the room. I have no substantive evidence to consider otherwise.

At 1m to the boundary, the proposed side extension would be a dominant built form from this window and would likely result in a reduction in natural light within the room. I have no technical evidence before me to quantify the level of light within the room. However, at such close proximity, the level of change in both outlook and natural light would, in my view, be significantly harmful.

Even if this was a secondary window to a single room, there would still be a degree of harm due to the cumulative effects on the side window, and the positioning of the side extension forward of the front building line. This, at 1m from the boundary, would still be an imposing feature from both the side and front window.

The single storey rear extension would stretch across the full width of the host dwelling and would therefore be visible from both neighbouring properties either side. However, it would be single storey with a flat roof and despite its projection to the rear, it would not therefore be unduly dominant or obtrusive at the height proposed. Moreover, as the attached dwelling has an existing rear extension and as No 43 is positioned further back than the host property, the proposed rear projection would not result in an undue sense of enclosure to either neighbour. Overall, given its distinctly low profile, it would not create an oppressive outlook from either of the neighbouring properties or their respective rear gardens. This does not, however, overcome my concerns regarding the effects from the side extension.

I therefore find that the proposal would have an unacceptable effect on the living conditions of the occupiers of No 43 with particular reference to outlook and light. The proposal would therefore conflict with the requirements of Policies DMHD1 and DMHB11 of the LP2, Policy D3 of the London Plan and the Framework insofar as they relate to this main issue. These stipulate, amongst other things, that planning applications relating to alterations and extensions of dwellings will be required to ensure that a satisfactory relationship with adjacent dwellings is achieved.

The appeal site is located within [name] 2 and 3 according to the Environment Agency’s published flood risk mapping. A Flood Risk Assessment (FRA) was submitted with the application. The Council are concerned that the FRA does not provide a commitment towards a [name] with no details regarding walls, windows, finished floor levels and soils.

The FRA provides an overview of the ground levels and a commitment to ensure that the finished floor levels of the ground floor extension would be no less than 300mm above the predicted 100-year flood level plus an allowance for climate change. The FRA proposes a soakaway and advises that the soils are sufficiently permeable. However, this is based on a desktop appraisal, with no substantive site-specific evidence or firm details of the soakaway system.

Overall, the FRA provides a broad strategy rather than a detailed site-specific drainage scheme. For example, there are no firm details of any additional hardstanding within the rear garden, giving access to the bifold doors from the extension. Moreover, there are no firm details of the existing rates and volumes of surface water run-off generated by the site, or specific details of the proposed size and location of the soakaway.

Flood risk and drainage matters are a material planning consideration and it is important that such matters are robustly addressed at the planning stage to ensure compliance with policies of the development plan. Taken together, although the proposal is for an extension to the existing dwelling, I share the Council’s concerns, that the level of information within the FRA is not sufficiently site specific and robust.

Based on the evidence before me, I can not therefore conclude that the proposed development would not increase the likelihood of flooding in the area. As such, the proposal would not accord with the requirements of Policy EM6 of the LP1, Policy DMEI9 of the LP2, Policy SI12 of the London Plan and the Framework, insofar as they relate to this main issue. These stipulate, amongst other things, that development proposals should ensure that flood risk is minimised and mitigated, and that residual risk is addressed.

For all the reasons given above, the proposal would conflict with the development plan and there are no material considerations that would outweigh that conflict.

Therefore, I conclude that the appeal should be dismissed.