Appeal 6002559

The appeal is dismissed.

The Council has indicated that there is an ongoing Local Plan review. I am not aware of the exact stage it has reached, the extent of unresolved objections or whether the policies concerned will be considered consistent with the National Planning Policy Framework (the Framework). Consequently, in accordance with Paragraph 48 of the Framework, I give it limited weight.

The main issue is the effect of the proposed development on the character and appearance of the host property and surrounding area with particular regard to whether it would preserve or enhance the character or appearance of the Strand on the Green Conservation Area.

The appeal site comprises a two-storey, mid-terraced dwelling, which has a two-storey rear outrigger. It is located within a short row of four similarly designed terraced properties.

The appeal site is located with the Strand on the Green Conservation Area (the SGCA). As the proposal is in a conservation area, I have paid special attention to the desirability of preserving or enhancing the character or appearance of that area, as set out in Section 72(1) of the Planning (Listed Buildings and Conservation Areas) Act 1990 (the Act).

The significance of the SGCA is derived from its intrinsically tranquil setting beside the water’s edge, with fishermen’s cottages, boat builders’ sheds, public houses, maltings and larger and more elegant private houses added in the late eighteenth century. The conservation area also includes the various modest but attractively detailed Victorian and Edwardian terraced housing. The appeal site is an example of an early [postcode] terraced property which contributes positively to the significance of the SGCA.

The proposed development includes a single storey wrap around extension, dormer extension to the rear roof slope and outrigger, the insertion of two rooflights within the front elevation. The Council has not raised any specific concerns in respect of the single storey extensions, rooflights or dormer extension to the original rear roof slope. Based on the evidence before me and my own observations, I see no reason to disagree with these conclusions. Therefore, this decision will focus on the effect of the proposal in relation to the dormer extension to the existing two-storey outrigger.

Policy CC1 of the Hounslow Local Plan 2015-203, adopted 2015 (the HLP), recognises the varied character of the Borough and states that all new development should seek to ensure that it conserves and takes opportunities to enhance the special qualities and heritage. Policy CC4 of the HLP also states that development should ensure that alterations and extensions respect the character of the building and surrounding area.

The Strand on the Green Conservation Area Appraisal (the [name]) identifies the inappropriate scale and character of roof, side and rear extensions, to maintain quality, skylines and sympathetic treatment as a threat to the SGCA. The Hounslow Character and Design Codes Supplementary Planning Document (the SPD) sets out that roof extensions over rear outriggers will normally be refused. It further states that dormer window extensions should be of modest size and not dominate the roof, as a rule they should be less than half the width of the original roof, set down from the ridge by 1 metre and set above the eaves by 1 metre.

The properties on this part of [address] all retain an original two-storey outrigger. Whilst most of the properties have been extended or altered, this feature is retained. The outriggers all have flat roofs and are set below the ridge height of the main roof slope, appearing subservient to the main part of the properties. I observed that these are typical features of many terraced dwellings within this part of the SGCA.

The proposed extension to the rear outrigger would extend this part of the property upwards to be the same height as the ridge height of the main roof slope, forming an l-shaped dormer extension, which would be largely viewed as a single addition to the roof slope. Whilst in isolation the extended part of outrigger would be a relatively modest addition in terms of floorspace, the height and bulk of the proposed addition alongside the main roof slope dormer would represent a bulky addition which would overwhelm the original form and proportions of the existing outrigger, host property and wider terrace. As a result, it would not be a subordinate addition.

I acknowledge that there are no residential properties immediately to the rear of the appeal site with the rear elevation of the property facing the railway embankment and being enclosed by some mature tree planting. However, whilst I accept that views of the rear elevation are limited from the wider public realm, it is visible from a pedestrian bridge over the railway, where it would be viewed as a bulky and discordant addition.

My attention has been drawn to an appeal decision1 at [address], where a dormer extension to an existing outrigger within the SGCA was allowed. However, I do not have the full details of that scheme, and the aerial image provided suggests a greater degree of variation in the roofscape, particularly in relation to the outriggers. On this basis, I do not consider it directly comparable to the appeal proposal, and I attribute it only limited weight.

Reference has also been made to [address], which lies within the SGCA and features a dormer extension above an outrigger that is not replicated on neighbouring properties. I have no details to confirm whether planning permission was granted for this addition. The Council advises that it predates the designation of the SGCA. Accordingly, it carries limited weight.

Further examples have been provided at 68–[address]. The appellant states that these properties were only recently included within an extension to the SGCA and that the presence of multiple dormer extensions above outriggers indicates they are an acceptable feature. However, I have not been provided with any information about the designation process, and there is no substantive evidence before me to demonstrate that these specific alterations were judged to be acceptable within the SGCA or that they establish a precedent for development of this form, scale or design.

With regard to [address], I understand that this area lies outside the SGCA. The recently issued lawful development certificate2 for a dormer extension above an outrigger is therefore not comparable to the current appeal, where planning permission is required due to the site’s location within the SGCA. I therefore afford this example limited weight.

I have also been referred to Nos 7, 8 and [address], which incorporate roof terraces above existing outriggers. While these demonstrate that various alterations have taken place within the SGCA, they are not directly comparable to the proposal before me. Moreover, the existence of development that is not in keeping with the character and appearance of the area does not justify permitting further harmful development.

The appellant has provided additional examples from [address], [address] and Whitehall Park Road. As all of these are located outside the SGCA, they are not comparable to the appeal proposal. In any event, each case must be assessed on its own individual merits, which is what I have done in making this

Whilst the appellant states that the proposal, in so far as it relates to the proposed dormer extension to the existing outrigger, would only result in a volumetric increase of approximately 34m3 and indicates that this would fall within the allowances set out under the Class B, Part 1, Schedule 2 of the Town and Country Planning (General Permitted Development) (England) Order 2015, these permitted rights do not apply in conservation areas. Consequently, I attribute this very limited weight. 1 Appeal Ref: APP/F5540/D/17/3172973 2 Application Ref: P/2024/1149

I have had regard to the appellant’s view that the Council places undue weight on the potential for an extension to ‘unbalance’ a pair or group of properties where only one seeks to alter its roof form. However, this is a matter of planning judgement which will depend on the specific characteristics of the proposal and its context. In this case, I find it is the combined scale, massing and position of the proposed extension that leads me to conclude that it would result in an unbalanced form of development, owing in particular to the extent of change it would introduce to the existing roofscape.

I acknowledge that the design of the dormer extension seeks to differentiate the new and existing elements through the use of contrasting materials, thereby retaining the legibility of the original outrigger. However, this approach does not mitigate the harm I have identified arising from the scale and bulk of the dormer extension.

For these reasons, the proposed development would cause unacceptable harm to the character and appearance of the host property and surrounding area, and thus, would fail to preserve or enhance the character or appearance of SGCA.

In failing to preserve the character and appearance of the SGCA, I find that the appeal proposal would, in the words of the National Planning Policy Framework (the Framework), result in less than substantial harm to the significance of a designated heritage asset. This harm would be at the lower end of the scale.

Paragraph 215 of the Framework states that where harm is identified to the significance of designated heritage assets and their setting, it should be weighed against the public benefits of the proposal. In this instance, the development proposed would provide additional accommodation for the appellant’s family. However, even in the context of the need to boost housing supply within London, and support for sustainable densification, this is a largely private benefit. Therefore, there are no public benefits which outweigh the less than substantial harm to the SGCA.

For these reasons, I conclude that the outrigger extension would have a harmful effect on the character and appearance of the host property and surrounding area and would therefore fail to preserve the character and appearance of the SGCA. Thus, it would be contrary to Policy HC1 of the London Plan and Policies CC1, CC2, CC4 and SC7 which seek amongst other things, to ensure that all new development conserves and takes opportunities to enhance their special qualities, conserve and enhance any heritage assets and be subordinate to the existing building.

The Council has not raised any concerns in relation to the effect of the proposed development on the living conditions of neighbouring properties. Based on the evidence before me and my own observations, I see no reason to disagree. However, the absence of harm is a neutral matter which neither weighs for nor against the proposal.

For the reasons given above the proposal conflicts with the development plan and the material considerations do not indicate that the appeal should be decided other than in accordance with it. Therefore, the appeal is dismissed.