East Sheen extension appeal allows 5.1m rear addition

The East Sheen extension appeal has succeeded, allowing a rear extension on Percival Road despite Richmond upon Thames Council’s concern about its effect on a neighbour’s outlook. Inspector SJ Desai granted planning permission on 9th October 2026 for a single-storey extension and roof alterations incorporating two roof lanterns. The approved scheme would create an overall rearward projection of about 5.1 metres.

The issue was whether the extra building would make the neighbouring home and garden feel unacceptably enclosed. Although the extension exceeds dimensions usually identified in the council’s guidance, the Inspector found that the gap between the houses and their angled relationship would soften its effect. This is permission for a particular design, not a change to extension rules across the borough.

I would look closely at that relationship before drawing conclusions from the headline dimensions. If you’re extending your home, the view from next door can matter as much as the measurements on your own plan. Here, the neighbouring property’s position meant that views towards its garden would remain, which helped the appeal succeed.

Why the East Sheen extension exceeded the usual guidance

The appeal property is a two-storey semi-detached home with an existing single-storey side and rear extension and a rear dormer. The proposal would add approximately 2.76 metres to the existing rear extension, taking the combined projection to around 5.1 metres. Its flat roof, including two roof lanterns, would be approximately 3.6 metres high.

Richmond’s House Extensions and External Alterations Supplementary Planning Document (SPD), published in 2015, advises that single-storey rear extensions to semi-detached properties projecting up to 3.5 metres will usually be acceptable. It also discusses limiting eaves heights for deeper infill extensions to reduce enclosure. This document provides detailed guidance alongside the council’s planning policies.

The East Sheen extension was deeper and higher than the dimensions generally identified in that guidance. The Inspector accepted that it would introduce more built form into the garden and would be noticeable from parts of the neighbouring property. He did not dismiss those effects or suggest that exceeding guidance was irrelevant.

But the guidance itself recognises that the final assessment depends on the particular site. Boundary distances, neighbouring layouts and the height of development all need to be considered. I would therefore avoid reading the usual 3.5-metre figure as either a guaranteed approval below it or an automatic refusal above it.

The bend in the road changed the neighbour relationship

The main concern related to the neighbouring property on the northern side, which has its own single-storey side extension. A physical gap separates the houses. Because Percival Road bends, that neighbour also sits at a slight angle to the appeal property, and the rear elevations are not aligned.

That arrangement meant the proposed extension would not sit directly across the neighbour’s principal view towards the back of its garden. Views beyond would remain available from its rear windows. The additional building would be apparent through the glazed rear opening in the neighbour’s side extension, but separation and orientation would moderate the impact.

The East Sheen extension decision therefore turns on more than the fact that there was already an extension next door. The Inspector examined which neighbour was affected, where its windows were and how the buildings faced one another. Those details explain why a relatively deep addition was acceptable here.

For anyone preparing a similar proposal, I would want drawings that make the neighbouring layout clear. A rear elevation alone can conceal an angled relationship, while an accurate site plan can show it immediately. The aim is to demonstrate what a person would actually experience from their home and garden.

A changed view was not unacceptable enclosure

The extension would also be visible from the neighbouring garden, especially near the boundary. However, much of that garden would retain an open aspect. The Inspector concluded that the single-storey building, combined with the houses’ separation and orientation, would not materially compromise its reasonable enjoyment.

Boundary vegetation offered some screening, but the Inspector gave that limited weight because it could be removed or altered. That matters if you’re relying heavily on a hedge to defend a design: the decision needs to consider what the relationship would be like if the vegetation changed.

The key conclusion was that the proposal would not create “an unacceptable sense of enclosure or an unduly overbearing relationship”. The East Sheen extension would change the outlook, but the Inspector found that the change would stay within acceptable limits.

I would keep that distinction in mind when responding to either an application or a refusal. Simply showing that an extension can be seen does not answer the planning question. The useful evidence concerns its scale, position and actual effect on the neighbouring rooms and outdoor space.

The policy assessment and the attached neighbour

The Inspector found no unacceptable harm to the northern neighbour’s living conditions, particularly its outlook. The proposal complied with Policy 46 of Richmond upon Thames’s Local Plan for 2024 to 2039, adopted in 2025, which seeks adequate outlook and avoids undue enclosure or overbearing effects.

It was also consistent with the underlying objectives of the council’s extension guidance. That conclusion followed a detailed assessment of the site, rather than a decision to set the guidance aside. The council had raised no objection to the effect on the attached house, taking account of that property’s existing rear extension.

The decision records that the National Planning Policy Framework published on 17th August 2026 was considered. The Inspector found that the relevant policy approach had not fundamentally changed and that neither party had been prejudiced. This appeal should not be described as succeeding because new national policy relaxed extension standards.

If you are comparing the East Sheen extension with your own proposal, make sure the comparison is fair. A house immediately alongside a neighbour’s principal rear windows may have a different effect from a separated house on a bend. Our planning appeals guide explains the appeal route, but each site’s evidence still needs its own assessment.

Conditions include a ban on using the roof as a terrace

The East Sheen extension permission requires development to begin within three years and to follow the approved plans. External materials must match those of the existing building. The extension’s roof cannot be used as a balcony, roof garden or similar outdoor amenity area, protecting neighbours from a different form of use above garden level.

A fire strategy plan is included in the approved documents. The Inspector considered a separate condition requiring compliance with it unnecessary because the approved-plans condition already secures that document. He also rejected a proposed condition about non-road mobile machinery as unnecessary and disproportionate for this limited development.

I would check the approved-plan list and conditions before agreeing the final construction specification. Permission for a flat-roofed extension does not mean you can later turn that roof into a terrace. Our planning conditions guidance explains how those requirements operate.

The full official appeal decision and Planning Inspectorate case record identify appeal 6014155 and application PA26/0566. The available record contains no separate costs decision, so this report makes no claim about a costs award.

For homeowners and neighbours, the useful next step is the same: establish the actual building relationship before arguing from a standard dimension. We can assess the planning issues and refusal reasons, helping you decide whether to revise the design or make an evidence-based appeal.