Appeal 6003971

The appeal is dismissed.

The Council raises no objection to the single-storey rear element of the scheme, and I agree that it is acceptable. My assessment therefore focuses on the proposed two-storey side extension.

The main issues are: • The effect of the two-storey side extension on the living conditions of the occupiers of 1 and [address], with particular regard to outlook and light; • Whether it has been satisfactorily demonstrated that the development would be safe from flooding and would not increase flood risk elsewhere; • The effect of the two-storey side extension on the character and appearance of the host building and surrounding area.

The appeal property is a two-storey end-of-terrace dwelling. To the north-west are 1 and [address] (Nos 1 and 3), a pair of semi-detached bungalows oriented perpendicular to the appeal terrace.

The rear elevation of No 3 contains ground floor living accommodation windows and a first floor dormer bedroom window that face directly towards the gable end of the appeal dwelling. The garden is short and the dividing boundary fence is modest in height.

The full-height flank wall of the two-storey side extension would rise substantially above the boundary fence. Owing to its proximity, height and massing, the extension would form a visually dominant feature that would materially increase the sense of enclosure experienced from the principal rooms and small garden at No 3. I therefore find that the two-storey side extension would result in a significant overbearing impact to the detriment of the living conditions of occupiers of No 3, notwithstanding the lack of objection from that neighbour.

I acknowledge that the removal of side-facing windows in the gable of the appeal property could improve privacy for No 3. However, this benefit does not negate or outweigh the harm that would arise from the increased sense of enclosure and harm to outlook identified above.

In terms of overshadowing, the appeal dwelling lies to the south-east of No 3. Although the two-storey side extension would be positioned close to the boundary, it would be no higher than the existing terrace, and the sun’s path means that any additional shadowing would be minor and limited to the morning. For most of the day the rear windows and garden of No 3 would continue to benefit from unobstructed daylight. I therefore do not share the Council’s view that there would be harmful overshadowing.

As the rear elevation of No 1 faces the open rear garden of the appeal property, the extension would not intrude materially into the primary outlook from its principal rooms, nor would it appreciably affect daylight or sunlight. I therefore find no unacceptable harm to the living conditions of the occupiers of No 1.

For these reasons, I conclude that the two-storey side extension would unacceptably harm the living conditions of the occupiers of [address] in terms of outlook, but not those at No 1. The proposal therefore conflicts with Policies CP4 and CP30 of the [name] 2010 (the CS), and Policies DMD8, DMD 11 and DMD 14 of the Enfield Development Management Document 2014 (the DMD), which collectively seek to safeguard the amenity of neighbouring occupiers.

The evidence before me indicates that [address] lies within [name] 2, with [name] to the rear forming part of a wider [name] 3 corridor. The Council’s SuDS Highway Services identify that the site is at risk from both surface water and fluvial flooding in the 1 in 100 year event including a +17% climate change allowance. This is consistent with the Strategic Flood Risk Assessment (SFRA), which records that the [name] catchment responds rapidly to rainfall and is affected by engineered channel constraints that heighten the sensitivity to extreme events. In such circumstances, a site-specific Flood Risk Assessment (FRA) is required to demonstrate that the development would be safe for its lifetime and that it would not increase flood risk elsewhere.

Although a FRA was submitted with the application, it does not address the specific sources of flood risk affecting the site. It provides no assessment of overland flow routes, nor does it quantify flood depths or hazards for the 1 in 100 year plus climate change scenario identified by both the consultee and the SFRA. The FRA also omits any proposal for level-for-level flood storage compensation.

The appellant’s SuDS pro-forma identifies an attenuation target of 6.97m3 for the 1 in 100-year event plus climate change, whereas only 2.55m3 would be provided. This is a substantial shortfall in provision, and no justification or alternative mitigation is advanced. A single SuDS feature of insufficient capacity would not ensure that runoff is managed close to source or maintain discharge rates at acceptable levels.

Policies SI12 and SI13 of the London Plan 2021 (the LP), together with [name] 21 and CP 28 of the CS and [name] 59–61 of the DMD, require development to be safe from flooding, avoid increasing flood risk elsewhere, and to incorporate SuDS in accordance with the established hierarchy. The SFRA emphasises the need for robust site-specific FRAs in locations subject to fluvial and surface water interaction, including ensuring no loss of flood storage and the provision of attenuation that accounts for climate change. In the absence of a reliable assessment of flood hazards, compensatory storage or a SuDS strategy capable of attenuating runoff for the critical storm events, I cannot be satisfied that the development would satisfy these requirements.

Although the appellant suggests that the Council could have requested further details, it is the responsibility of the applicant to provide sufficient information at the point of determination to demonstrate that the proposal satisfies the relevant flood-risk and drainage requirements. Given the importance of the deficiencies identified, which relate to the fundamental question of whether the development can operate safely and without increasing flood risk, it would not be appropriate to leave such matters to planning conditions.

For these reasons, it has not been demonstrated that the development would be safe from flooding and that it would not increase flood risk elsewhere. The proposal is therefore contrary to the flood-risk and drainage objectives of the policies listed above, and section 14 of the National Planning Policy Framework.

The Council expresses concern that the two-storey side extension’s width, height and proximity to the boundary would create an impression of a terracing effect with [address].

However, No 3 is a single-storey dwelling (with dormer), oriented at a right angle to the appeal terrace and separated by its rear garden. Given this geometry, the proposed extension would not read as part of a continuous facade and no realistic terracing effect would arise. Even in the absence of a 1-metre gap from the boundary, a clear spatial break would remain, preventing any perception of the dwellings merging visually.

Furthermore, I do not consider that a set-down or set-back at first floor would be appropriate in this case as it would introduce an awkward and visually disruptive step into the otherwise simple roof form of the terrace. By maintaining the established roofline, the extension would sit comfortably with the form and proportions of the host building.

I therefore conclude that the two-storey side extension would not harm the character or appearance of the host building and surrounding area, and so, complies with the design objectives of Policies D3 and D4 of the LP; Policies CP4 and CP30 of the CS; and Policies DMD6, DMD8, DMD14 and DMD37 of the DMD.

The appellant refers to several extensions that have been built in the surrounding area. However, each proposal must be assessed on its own merits. Here, the specific relationship between the appeal dwelling and [address], together with the site-specific flood-risk and drainage considerations, are determinative factors. These circumstances are not shown to be replicated in the examples cited, which consequently carry little weight.

I recognise that the proposal would improve the internal accommodation available to the occupiers of the appeal property. However, this benefit does not outweigh the harms identified in respect of neighbouring living conditions and flood-risk.

While the single-storey element is acceptable, the development as a whole would cause unacceptable harm to neighbouring living conditions and fails to demonstrate compliance with flood-risk and drainage policy requirements. These harms are decisive. The proposal therefore conflicts with the development plan taken as a whole and there are no material considerations to justify a decision otherwise. Accordingly, the appeal should be dismissed.