Appeal 3373495

The appeal is allowed and planning permission is granted for erection of single storey extension to the rear, first floor rear extension, conversion of roof space to habitable use to include 4 side dormers, 2 rooflights and 2 new gable end windows at [site address] , Hillingdon, [postcode] , in accordance with the terms of the application, Ref 282/APP/2025/1939, subject to the following conditions:

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

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

The development hereby permitted shall be carried out only in accordance with approved plans [name]-3001, 3002, 4001 [name] and 4002 [name], dated 18 December 2024.

The side windows in the first-floor dormers shall be permanently fixed shut and obscure glazed below a level of 1.8m above the adjacent floor.

The application was in terms of a 3m deep first floor rear extension, but the Council considered the proposal as described above, including elements of the two previous approvals for more extensive rear and roof extensions. Neither of these have commenced, and the Council makes the distinction between those approvals and the further extension now proposed. I have followed the same approach, as this takes account of proposed internal changes having a bearing on residential amenity.

The application was refused solely on the grounds that the outlook from a proposed bedroom in the extension would not be acceptable, and this constitutes the main issue for consideration in this appeal.

It is material that the appeal bungalow is the subject of a lawful development certificate1 giving consent for four flat-roofed side dormers providing first floor accommodation in the present bungalow, with access via a staircase in the front part of the ground floor.

The present proposal repeats the four side dormers but adds a rear first floor extension over a previously approved flat-roofed, ground floor living-dining extension2. The proposal also rearranges the internal accommodation to facilitate placing the staircase to the upper floor towards the rear of the house. Neither of the previously approved schemes have commenced but their approvals are extant, providing a material fallback position.

The Council itself notes that the character of the area is defined by detached bungalows which have been much extended, largely by way roof dormers within permitted development limits. The Council acknowledges that the additional first-floor rear extension would add further massing to the extended property, albeit reduced in bulk since a previous refusal, but would appear subordinate in scale and height to the main roof.

From my inspection of the site and surroundings, I agree with the Council that the level of harm that would result from the cumulative bulk and massing of extensions now proposed to the appeal property, given the previous approvals and permitted development fallback, would not be sufficient to justify dismissing this appeal. To that extent, on balance, the present proposal would not undermine the aims of London Plan and Hillingdon Local Plan (HLP) policies regarding design quality and respect for local character.

Turning to the main issue of outlook. This is only part of the proper consideration of the appeal proposals in terms of the potential effects of the development on residential amenity.

I am in further agreement with the Council that the new first floor rear extension would be unlikely to result in a significant loss of light to neighbouring properties at Nos 93 and [address], compared with the ground floor rear extension already approved. I also agree that, with the use of obscure glazing and limited window opening in the side dormers, there would be no increased loss of privacy, compared with the built development which benefits from extant consents.

The main amenity concern relates to the rear first floor bedroom, as now proposed. Occupants the first floor, back master bedroom, as previously approved, would have enjoyed an open view out of the rear window. The first-floor extension and staircase now included would remove this source of light and outlook and the bedroom in question would only be served by side dormer windows fixed shut with obscure-glazing below 1.8m above floor level. 1 282/APP/2024/144 2 282/APP/2024/254

The Council judges this arrangement to be unacceptable in terms of Policies DMHB11and DMHD1 respectively of the HLP Development Management Policies as well as Policy D6 of the London Plan, together seeking good design avoiding adverse impacts, such as poor outlook and inadequate natural lighting available to residents.

I agree with the Appellant that reliance upon side windows with clear glazing and opening only above 1.8m from floor level is commonplace and that this does not mean that natural lighting levels would be inadequate. But that is not the point. The outlook from the disputed bedroom would be restricted, specifically to avoid overlooking.

Importantly however, the side view from all the first-floor bedrooms, apart from the front master ensuite room, would be towards the side of the neighbouring property and therefore quite limited in any case. In my judgement, the practical harm in terms of the reduced outlook from one of these rooms would be insignificant in the circumstances.

As a result, I do not consider that the outlook from the rear bedroom of the appeal dwelling, as now proposed, would be unacceptable, nor that the present appeal proposals would be in undue conflict with the relevant development plan polices cited above.

I accordingly conclude that this appeal should be allowed.

The Council suggest without prejudice only the standard conditions requiring compliance with approved plans and the use of matching materials. But this approval creates a new permission that sits beside those previously granted but not commenced and still extant, such that it is for the developer to choose which permission to implement. Therefore, I consider it necessary to impose express condition 4 to secure the obscure glazing and restricted opening of the side dormer windows, as referenced in the written representations of both parties.