Appeal 3370749

The appeal is allowed and planning permission is granted for a single storey rear extension at [site address] , Hounslow [postcode] in accordance with the terms of the application, [name]/2025/0877, subject to the following conditions:

The development hereby permitted shall begin not later than 3 years from the date of this decision.

The development hereby permitted shall be carried out in accordance with the following approved plans: PL-01, PL-02 [name] and PL-04 [name]

The materials to be used in the construction of the external surfaces of the development hereby permitted shall match those in the existing building.

Before the first use of the roof terrace part of the development hereby permitted the existing fence/screen at first floor level between the appeal dwelling and [address] will be retained or replaced with a matching fence screen.

The main issues are the effect of the proposal on: • The living conditions of neighbouring residential occupiers; and • The character and appearance of the host dwelling and that of the Osterley Park Conservation Area (the CA).

The appeal dwelling is a generously proportioned two storey semi-detached house, with an attached garage to its flank and large front and rear gardens. The house has undergone previous extension to the rear and roof level, with additional living space in the loft.

The proposed extension would replace an existing structure providing an area for storage to the rear of the existing storage. It would extend across the full width of the appeal dwelling and side garage, integrating with the existing rear infill extension, which would involve the creation of a single large roof terrace that would span across the roof of the garage and infill extension. The roof of the proposed brick built extension to the rear of these would be mono-pitch in form and tiled to match those of the main house and 4 flush rooflights.

The application plans show an existing balustrade to the edges of the garage roof and part of the rear infill extension. On my site visit it was evident that this balustrade was not in place, there is however a door from the first floor of the appeal dwelling that would provide access to this space. A balustrade is however proposed that that would be to the edges of the large first floor terrace that would result from the proposal.

The proposed extension would infill the existing open area between the storage room garage and the boundary of the appeal dwelling’s semi-detached pair at [address] (No.178). The boundary between the appeal dwelling and No.178 at this point is made up of a tall, rendered panel, which appears to be in excess of 2 metres in height. At first floor level there is also a close boarded fence/screen on the boundary between the existing infill rear extension to the appeal dwelling and No.178.

The proposal would result in the new extension and the whole of the roof of the infill extension matching the existing height of the garage along this boundary with No.178. This would add only slightly to the sense of enclosure to the ground of No.178 and that part of its rear patio nearest to the house. This would not result in an additional sense of enclosure to an already enclosed space that would be experienced by the occupant’s as oppressive, when compared to the existing situation.

The proposed terrace area at first floor level would allow views across the gardens of neighbouring properties, but not to any greater degree than is possible from existing rear windows in the appeal dwelling. There is an existing roof terrace with balustrade and access stair at No.178 that provides for views over the garden and rear of the appeal dwelling. A degree of mutual overlooking between roof terraces is, therefore, to be expected.

Views into the rear rooms of [address] would be screened by the rearward extent of this neighbouring house and its flank, which sits close to the boundary that it shares with the appeal dwelling. Views into the rear rooms of No.178 would be screened by the existing close boarded fence between the two at first floor level, which appears to be shown as retained on the submitted plans. The retention or replacement of this first floor fence/screen could be secured by the attachment of a suitably worded condition on an approval. The proposal would not therefore lead to an additional degree of overlooking of neighbouring properties that would be experienced by their occupants as intrusive to the extent that they would result in any significant loss of privacy.

The proposal is designed to be finished in materials that would match with those used in the original house. The appeal dwelling already has a rear storage room that reaches rearward from the garage almost to the same extent as the proposed full width rear extension. The proposed new rear extension would project 3.65 metres from the rear of the garage and existing rear infill extension, across the full width of the appeal dwelling and garage.

The design guidance in the [name], Sustainability and [name] A5 [name] (2021) (the SPD), advises that rear extensions should be kept to a projection from the rear wall of the original house of 3.65 Metres. It does not however provide advice when there are existing extensions to the original house or to neighbouring properties, or where the extension is to a more generously proportioned house, such as the appeal dwelling. The design guidance in the SPD is advice that should be applied to the circumstances and context. In this instance that means taking account of the generous proportions of the appeal dwelling and neighbouring properties and of existing extensions, to both the appeal dwelling and neighbouring dwellings.

Although reaching further rearward than existing the storeroom extension and infilling an existing open area of rear garden space, the proposal would represent a significant rationalisation of the various forms and designs that make up the existing rear additions and roof profiles. This would result in the proposal as a whole appearing proportional to the scale of the appeal dwelling. As a result, the proposal would appear as a complementary change to the rear, which would appear as being more congruent with the character of the existing house and as a secondary and subordinate addition. As such it would not have any detrimental effect on the character and appearance of the appeal dwelling.

The appeal dwelling is located in the southern part of the (CA), the significance of which rests in the park itself and the townscape that provides its wider setting, to which the appeal dwelling makes a contribution. In line with the duty imposed on me by section 72(1) of the Planning (Listed Buildings and Conservation Areas) Act 1990, I have given considerable importance and weight to the desirability of preserving or enhancing the character or appearance of the CA.

For the reasons given, the proposal would appear more congruent with the character and appearance of the appeal dwelling than the existing, albeit smaller, extensions, and the proposal would have no detrimental effect on the character appeal dwelling. It would also only be visible in limited views of the rear of the property from private vantage points and would not be readily visible from any public vantage point. As such the proposal would preserve the character and appearance of the CA and have no effect on the contribution that the appeal dwelling makes to its significance. For these reasons, I find that proposal would accord with the SPD’s design objective of preventing extensions that harm the character of the house and local area, protecting the significance of heritage assets, including conservation areas, or detracting from the living conditions of neighbouring residential occupiers.

For the reason given above, the proposal would not result in any significant harm to the living conditions of neighbouring residential occupiers or harm to the character or appearance of the appeal dwelling or that of the CA. As such it would accord with Policies CC1, CC2, CC4 and SC7 of the Hounslow Local Plan 2015- 2030 (2015). Amongst other matters these seek developments, including by extension, that are of high quality urban design and architecture, which creatively respond to the areas character, do not harm the existing character and appearance of the building and its context, conserve the significance of heritage assets and protect the amenity and living conditions of occupiers of neighbouring dwellings.

I have had regard to the Council’s suggested conditions should I be minded to allow this appeal. I have not included the suggested condition regarding the potential for the creation of openings in the side elevations, as either a planning permission would need to be sought, or there are no exceptional circumstances that have been brought to my attention that would justify the removal of any permitted development rights. There are therefore no planning reasons that would make such a condition necessary.

As part of their appeal submission the appellant suggested reducing the extent of the roof terrace and surrounding balustrade. In considering the proposal as originally submitted, I have found it to be an acceptable development proposal. Attaching a condition requiring this reduction in extent of the roof terrace and balustrade would not, therefore, be necessary to make the development acceptable.

Along with the standard condition regarding the timing of implementation, in the interests of good design I have attached conditions requiring compliance with approved plans and matching materials. In the interests of privacy, I have attached a condition requiring the retention or replacement of the existing first floor fence/screen.

The appeal is allowed.