Appeal 3359746

The appeal is dismissed.

At the time of my visit I saw that the development had already been carried out and was substantially complete. I observed the size and form of the extensions to the side and rear of the original dwelling generally conform to that which is shown on the planning application’s drawings although there were some noticeable differences to the fenestration pattern between the plans and the works that have been undertaken.

The application form described the proposed works as a ‘Single storey infill extension’. My description in the banner heading above uses that which was given by the Council on their decision notice and which was repeated by the appellant on the appeal form. This gives a more complete and accurate description of the entirety of the works.

The main issues are the effects of the development upon the living conditions at [address] with particular regard to visual impact and privacy, and its effects upon flood risk.

The appeal property is a two-storey, semi-detached dwelling occupying a wedge-shaped plot to one side of a hammerhead turning at the end of a short residential cul-de-sac. Land levels to the rear of the dwelling fall away towards the rear of the site. The dwelling has been extended with a two-storey side and rear addition which is set away from the shared common boundary with the attached property at [address] and with a deeper single-storey rear element that spans the full width of the original dwelling and which projects beyond, and marginally wraps around, the extended dwelling’s side elevation. Beyond the single-storey projection is a raised patio. The finished floor levels of the patio and extensions run contiguous with the ground floor level of the original building. The single-storey extension projects 6m beyond the original rear wall of the dwelling adjacent to the shared boundary with No 6. It measures just over 2.7m in height above the finished floor level of the extension and original dwelling and, together with the patio, a further 900mm above the levels of the garden according to the figures given on the planning application drawings.

The Council’s Residential Design Guide Supplementary Planning Document (SPD), adopted in 2010, deals with single-storey rear extensions at paragraphs 6.59 – 6.63. It advises that the depth of extensions beyond the 3m that would normally be permitted development for a semi-detached dwelling will be considered having regard to, amongst other things, the scale of development and impact on the amenity of neighbouring residents. It goes on to say that depths greater than 3m may be allowed where either the extension would be sited away from an adjacent side boundary; the rear building line is staggered; an adjacent dwelling is sited away from such a boundary; or where the neighbouring dwelling has a deeper extension. It further advises that the finished height of a flat roof extension abutting a residential property should be a maximum of 3m high on the boundary.

During my visit I was able to stand on the raised patio to the rear of the extended dwelling and observe the relationship between the single-storey rear extension and patio and No 6. These elements of the development appear consistent with the planning application drawings. I observed that the attached property at No 6 is unextended to the rear. The height of the extension, at 3.6m above natural ground level, exceeds the SPD’s guidelines. Neither the site-specific circumstances nor the relationship between the appeal property and the attached dwelling at No 6 suggest to me that the single-storey part of the extension reflects a size of development that is supported by the SPD.

The flank wall of the extension rises significantly above the height of the approximate 1.8m high fence which runs along the boundary at ground level between both properties. Its overall height extends well above the height of any conventional residential boundary enclosure. I do not share the appellant’s view that the extension is no more dominant than the existing boundary treatment. On the contrary, I find that due to its proximity, height and depth, the extension has imposed itself upon the outlook from the nearest ground floor living space at No 6, and upon the immediately adjoining outdoor amenity space, as an overbearing and visually intrusive solid built form which has created an unacceptable sense of enclosure within the neighbours’ back garden setting.

When standing on the patio, the existing boundary fence between the appeal property and No 6 extends approximately to waist height. From this elevated position there is direct sight into the neighbours’ rear garden, including looking back towards the rear elevation and into the more private parts of the adjoining outdoor amenity space. This is highly intrusive and significantly detrimental to the levels of privacy the neighbours may reasonably expect to enjoy. The appellant has suggested that a 1.8m high privacy screen could be erected running along the side of the patio to address the problem of overlooking. No such details have been submitted to demonstrate how this may be achieved. Whilst it may be reasonable to secure such screening by condition, the result would be further enclosure deep along the boundary shared with No 6 and well above the height of a conventional fence. This would have the potential to appear visually intrusive and overbearing in its own right. It would not be an acceptable way to mitigate the harm that has arisen from the height and position of the raised patio that has been constructed.

Overall, for the reasons given, I find the development to be significantly harmful to the living conditions at [address]. By failing to achieve a high standard of privacy and amenity of neighbouring occupiers the development directly conflicts with Policy DM1 of the Harrow Development Management Policies, adopted in

There would also be conflict with the similar aims included within Policy GR1 of the emerging Harrow Local Plan 2021-2041, which I note is at an advanced stage of preparation.

I am mindful that planning permission was granted in April 2024 for development described as ‘Two storey side to rear extension; single storey rear extension; rooflights in front and rear roofslopes; external alterations (part demolition of detached garage and canopy at rear)’ ([name]/2576/23). The approved scheme is similar to the development that has been constructed. Crucially however, the maximum height of the single-storey extension above ground level was shown on the approved plans to be 3.15m. Furthermore, the approved scheme did not include a raised patio beyond the single-storey extension. The weight I attach to the past planning permission does not outweigh the harm that I have identified.

The site lies within a Critical Drainage Area. The appellant has submitted a Flood Risk Assessment and Sustainable Urban Drainage Assessment Report (the report) dated 29 January 2025 which states that following a review of the [name] Assessment GIS mapping, the only source of flood risk at the site is surface water. The flood risk assessment sets out proposals for managing surface water drainage at the development in the form of attenuation in rain planters using SuDS techniques. It concludes that the proposed surface water strategy would achieve a positive reduction in flood risk.

I have no reason to doubt the contents and findings of the report. [name] been minded to allow the appeal, I am satisfied that the provision of rain planters could have been secured within a specified timeframe by condition. In these circumstances there would be no conflict with local, London Plan, or national policy requirements as far as they relate to flood risk and mitigation.

Notwithstanding my findings on the second main issue, for the reasons given above, the appeal is dismissed.