Appeal 6004596

The appeal is allowed and planning permission is granted for erection of a replacement two-storey side extension with a glazed link, erection of a rear infill extension, and reduction of side dormer with reinstatement of hip to front roofslope and installation of rooflight, construction of a new front dormer matching existing dormer on neighbouring property, along with other alterations to the existing building and boundary treatments at [site address] in accordance with the terms of the application, Ref. P2025/2468/FUL, subject to the conditions set out in the attached schedule.

The main issue is whether the development preserves or enhances the character or appearance of the Canonbury Conservation Area (CA), having regard to its effect on the significance of the locally listed building at [site address] .

The appeal site comprises a mid‐nineteenth century semi‐detached villa within the CA. The building is locally listed and is a Non‐Designated Heritage Asset (NDHA). Its significance derives from its architectural form and proportions, its relationship with the adjoining villa, and its contribution to the spacious and leafy character of this part of Northampton Park.

The significance of the villa and its contribution to the character and appearance of the conservation area have been diminished by a number of later unsympathetic alterations. These include the construction of a bulky two‐storey side extension, the addition of an oversized side dormer, and an awkward linking structure incorporating a street‐facing entrance and balcony. These features detract from the Appeal Ref: 6004596 original architectural form and interrupt the sense of separation between buildings which is characteristic of the street.

The appeal proposal would retain the original villa but significantly alter the later additions. Most notably, the existing oversized side dormer would be removed entirely, allowing the hip to the front roof slope to be reinstated. A smaller front dormer, comparable in scale and position to that on the adjoining property at No. 8, would provide replacement accommodation. Importantly, the primacy of the original villa, identified by the Council as a key concern, would be retained and reinforced through the removal and rationalisation of unsympathetic additions. Taken together, these changes would result in a more coherent and legible roof form and would reduce the prominence of roof additions in both public and private views. Compared with the existing situation, this would represent an improvement to the appearance of the host building and its contribution to the conservation area.

The proposal would also replace the existing side extension and link with new structures of reduced overall height and simplified form. The removal of the projecting street‐facing balcony and the incongruous entrance door within the link would reduce visual clutter and introduce a clearer distinction between the original building and later additions. I note the Council’s concerns that the proposed fenestration, particularly to the rear, would compete with the host building and fail to respect its established window hierarchy. However, the proposed openings would be read in the context of a clearly secondary addition and subject to their detailed execution, would not in my view undermine the legibility or architectural coherence of the original villa. The glazed link, by reason of its lowered height and recessive appearance, would read as subordinate to the historic villa and would allow greater visual separation between elements of the building.

Concern has been raised by interested parties and the Council regarding the contemporary design approach and the use of reflective metal cladding for the replacement side extension. It is considered that this would appear incongruous within the CA, fail to respond to its character, and accentuate the scale and prominence of the extension. I have carefully considered these concerns. While the proposed material would differ from the traditional palette of brick and stucco found elsewhere within the CA, the use of contrasting or contemporary materials is not, in itself, harmful. The critical consideration is whether, in the context of the proposal as a whole, the design and materiality would impede the appreciation of the significance of the locally listed building or would harm the character and appearance of the CA.

In this case, I am not persuaded that it would do so. The replacement extension would remain subordinate in scale and massing to the original villa and would be contained within the established gap between buildings that contributes to the area’s spacious character. The reduced height and simplification of form would lessen the visual impact of built development on the plot when compared with the existing extension. Importantly, the proposal would not obscure or compete with key architectural features of the historic villa, nor would it erode important spatial relationships within the street.

The proposal also includes the introduction of a front dormer. I recognise that front dormers can, in some circumstances, harm the balance of semi‐detached villas and detract from the character of conservation areas. The Council considers that ‘balancing’ the roofscape by reference to an adjacent, visually harmful dormer is Appeal Ref: 6004596 not a justifiable argument for causing further architectural harm. I agree that the presence of an unsympathetic feature on a neighbouring property does not make a similar addition acceptable. However, in this instance, the adjoining property already contains a front dormer of comparable scale and position, and the proposal must be considered in the context of the roof alterations as a whole. When considered in that context, and alongside the substantial reduction in the scale of the existing side dormer, I find that the roof alterations would result in a more coherent and balanced overall roofscape than exists at present.

I have paid special attention to the desirability of preserving or enhancing the character or appearance of the CA, as required by section 72(1) of the Planning (Listed Buildings and Conservation Areas) Act 1990. I have also taken account of the effect of the proposal on the significance of the locally listed building, as a NDHA.

Drawing these matters together, I conclude that the proposal would not harm the significance of the locally listed building nor the character or appearance of the CA.

The development therefore accords with Policies DH1 and DH2 of the Islington Local Plan (adopted 2023), which seek to conserve heritage assets and ensure development within conservation areas preserves or enhances their significance, and with Policy HC1 of the London Plan (adopted 2021), which requires development to conserve the significance of heritage assets. For similar reasons, I find no conflict with Chapter 16 of the National Planning Policy Framework, which seeks to conserve and enhance the historic environment.

In imposing the above conditions, and in the absence of a detailed schedule of conditions from the Council, I have drawn on the matters identified in the delegated report, including consultee comments. I have also had regard to the tests for planning conditions set out in paragraph 57 of the National Planning Policy Framework and the guidance in the Planning Practice Guidance.

A standard time‐limit condition is imposed in the interests of certainty. A condition requiring the development to be carried out in accordance with the approved plans is necessary to ensure that the development is implemented as assessed. Conditions requiring the submission and approval of details of external materials and detailed junctions are imposed to secure an appropriate quality of design and to ensure that the development preserves the character and appearance of the CA and the significance of the locally listed building. A condition securing further details of sustainability and biodiversity measures reflects matters identified in the delegated report as appropriate to be addressed through conditions should permission be granted and is proportionate to the scale of the development. A separate condition is imposed to secure replacement tree planting to mitigate the loss of the sycamore tree and to safeguard the verdant character of the area. Appeal Ref: 6004596

For the reasons given above and having had regard to the development plan as a whole and to all other matters raised, I conclude that the appeal should be allowed.

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: Location Plan, NPL/PL/101 [name], NPL/PL/102 [name], NPL/PL/103 [name], NPL/PL/104 [name], NPL/PL/105 [name], NPL/PL/106 [name], NPL/PL/107 [name], NPL/PL/108 [name], NPL/PL/109 [name], NPL/PL/110 [name], NPL/PL/111 [name], NPL/PL/112 [name].

Notwithstanding the submitted details, no development above ground level shall take place until samples and full details of all external materials and finishes have been submitted to and approved in writing by the local planning authority. The submitted details shall include: • the finish, colour and surface treatment of the metal cladding, • details of glazing, framing, and reflectivity, • and details of all proposed brickwork, roofing, and rainwater goods. The development shall thereafter be carried out in accordance with the approved details.

Prior to the installation of any external materials, detailed drawings (at a minimum scale of 1:20) of the following shall be submitted to and approved in writing by the local planning authority: • window and door reveals, • junctions between the extension and the host building, • eaves, parapet and roof edge details, and • the interface between the glazed link and the original building. The development shall thereafter be carried out in accordance with the approved details.

Prior to first occupation of the development hereby permitted, a Sustainability and [name] shall be submitted to and approved in writing by the local planning authority. The Strategy shall confirm and/or provide: Appeal Ref: 6004596 • Energy performance details for new/altered building elements, including U‐values for walls/roofs/floors and U‐ and G‐values for glazing • Overheating mitigation measures, confirming the proposed means of natural ventilation and any internal shading relied upon • Biodiversity features, including the type and locations of any swift/bird boxes and bee bricks; and • A planting schedule for proposed soft landscaping (species and sizes). The recommendations in the Strategy shall be adhered to for the lifetime of the development.

Prior to the removal of the sycamore tree, as identified as T1 on drawing T003 (Tree Protection Plan), a Replacement Tree Planting Scheme shall be submitted to and approved in writing by the local planning authority. The Scheme shall include: • the number of replacement trees • species • size at planting (height and girth) • locations; and • a five‐year maintenance and replacement programme. The approved replacement trees shall be planted in the first planting season following removal (or the first available planting season thereafter). Any tree which dies, is removed, or becomes seriously damaged or diseased within five years of planting shall be replaced in the next available planting season with one of a similar size and species, unless otherwise agreed in writing by the local planning authority.