Appeal 3295916

The appeal is allowed and planning permission is granted for demolition of a rear lower ground floor extension and construction of a part three, part single storey rear extension with 2 x dormer roof extensions to the rear. Roof-lights to the front roof, new staircase access to front light-well. Removal and replacement of existing uPVC windows with new timber sash windows to match at [site address] , Mortlake, London, [postcode] in accordance with the terms of the application, Ref 21/3692/HOT, dated 27 September 2021, subject to the following conditions:

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

The development hereby permitted shall be carried out in accordance with the following approved plans: P300 P2; P301 P2; P302 P2; P303 P2; P304 P2; P305 P2; P306 P2.

The materials to be used in the external finishes (including fenestration) of the development hereby permitted shall match those used in the existing building except where otherwise submitted in the original planning application.

The roof areas of the extensions hereby permitted shall not be used as a balcony, terrace, roof garden or similar amenity area nor shall any access be formed thereto.

The lower ground floor of the development hereby approved shall not at any time form bedroom accommodation.

The development hereby approved shall not be carried out other than in accordance with the approved [name] (SuDS) and Flood Risk Assessment (FRA) Report produced by Gray Environmental Limited and dated 19 October 2021.

Before installation, details of the proposed timber sash windows, including plans, elevations and sections at a scale of not less than 1:20 shall be submitted to and approved in writing by the local planning authority. Following approval the windows shall be constructed and installed in accordance with the approved details.

There is one main issue which is the effect of the proposed three storey rear extension on the character and appearance of the host building, the adjoining terrace and the surrounding area, including the Mortlake Conservation Area.

The Council’s reason for refusal relates only to the proposed three storey rear extension. I agree that the other elements of the proposed development would be acceptable. I shall therefore limit my further consideration to the disputed three storey rear extension.

The appeal dwelling is an end terrace, one of three similar houses fronting [address] and backing towards the [name]. The terrace can only be glimpsed from the river and tow path due to substantial development in between. The terrace dates from around 1850 and is locally listed as a Building of [name] (BTM). The terrace lies within the Mortlake Conservation Area (CA) which I s characterised in this area by older buildings interspersed between newer development, by its proximity to the river and by the pedestrian links between the [address] and the Thames towpath.

The National Planning Policy Framework (NPPF) makes clear that conservation areas and listed buildings are designated heritage assets. When considering the impact of a proposed development on the significance of a designated heritage asset, the NPPF advises that great weight should be given to the asset’s conservation. Significance can be harmed through alteration of the heritage asset or development within its setting. Statutory protection is provided by Section 66(1) and Section 72(1) of the Planning (Listed Buildings and Conservation Areas) Act 1990 (the 1990 Act) which apply to conservation areas and listed buildings respectively. These require that special regard/attention is paid to the desirability of preserving or enhancing the character or appearance of the heritage asset, including its setting.

The appeal dwelling is set over three floors, including a lower ground floor. Steps rise to the front door. It lies adjacent to a modern flatted development which is both higher and deeper than the appeal dwelling. Both of the other houses in the terrace have existing, full width, single storey rear extensions similar to the one proposed at No 109. In addition, the dwelling at the other end of the terrace has a two storey rear extension, similar to but one floor lower 2 than the three storey extension proposed. This occupies some two thirds of the width of the dwelling.

The Council is concerned that the combined height, width and siting of the proposed three storey extension would result in an unsympathetic form of development. However, rear outriggers of about two thirds the width of the dwelling are commonly seen on houses of this age and relatively narrow design and I see no reason why the width of the proposed extension would not harmonise with the rear elevation of both the dwelling and the terrace.

In terms of its height, the extension would finish with a flat roof just below eaves level. It would sit close to the higher and deeper side wall of the adjacent flats which would limit its presence and the original roof of the dwelling would continue to be read as a separate entity, preserving the historic form of the house. This would result in a sympathetic form of development that would not detract from nor overwhelm the original dwelling.

The Council suggests that in accordance with its Supplementary Planning Document (SPD) “[name] and [name]” 2015, a two storey or greater rear extension should be no more than half the width of the dwelling but in this case that would result in an odd form of development that would appear squashed and would fail to reflect the style of the original house. Moreover, the rear of the original dwelling and the terrace as a whole does not display symmetry and so the proposed extension would not have an unbalancing effect.

The Council suggests that only ground and first floor rear extensions are characteristic of the area and that the proposed extension would thus be incongruous. However, other nearby dwellings are noticeably larger and taller than the appeal dwelling and of a different architectural style and so are not readily comparable. Moreover, although the extension at No 113 is a floor lower than that proposed, it does not abut a larger building and is therefore more prominently sited on the rear of the dwelling.

Overall, in terms of the effect on the BTMs and the CA the effect of the proposed extension would, owing to its sympathetic design, subservient scale and inconspicuous siting, be neutral. It would therefore preserve the character and appearance of the non-designated BTMs and the CA and would thus comply with the requirements of the NPPF, national legislation and Policy LP3 of the Local Plan (LP), 2018, which requires development to conserve the historic environment of the borough, insofar as they seek to preserve the character or appearance and significance of heritage assets. 12.It is concluded on the main issue that the proposed three storey rear extension would have no materially harmful effect on the character or appearance of the host building, the adjoining terrace or the surrounding area and would conserve the significance of the Mortlake Conservation Area. In consequence, it would comply with [name] LP1, LP3 and LP4 which, taken together, expect development to be of a high architectural and urban design quality such that it is compatible with local character and conserves the historic environment, including both designated and non-designated heritage assets. 13.Turning to conditions, I agree with the Council that in addition to the statutory commencement condition, conditions requiring the development to be carried 3 out in accordance with the approved plans and in materials that match the existing or are as submitted are necessary in order to provide certainty and to protect the character and appearance of the host building and the surrounding area. In addition, I agree that detailed drawings of the proposed replacement windows should be submitted and approved in order to protect the historic character and appearance of the dwelling. A condition prohibiting the use of the flat roofs as a balcony or terrace is necessary to protect the living conditions of neighbours with respect to privacy. Owing to the potential for flooding from groundwater, I agree that bedroom accommodation should not be provided at lower ground floor level. 14.Finally, to minimise flood risk and promote sustainable drainage the development should be carried out in accordance with the [name] (SuDS) and Flood Risk Assessment (FRA) produced by Gray Environmental Limited and dated 19 October 2021. I have adjusted the suggested wording of conditions where necessary to comply with the tests for planning conditions set out in the NPPF and for clarity. 15.The Council suggests a condition limiting powered construction equipment used on site to that capable of running on ultra-low sulphur diesel. However, whilst that may be good practice, I do not consider that this condition is necessary or reasonable in terms of making the proposed development acceptable in planning terms and I shall not therefore impose it.

For the reasons set out above and having regard to all other matters raised, I conclude that the appeal should be allowed.