Appeal 6005232

The appeal is dismissed.

The main issue is the effect of the proposed development on the character and appearance of the host dwelling and the surrounding area, including whether it would preserve or enhance the character or appearance of the Harlington Village Conservation Area (CA).

The appeal property is a two-storey semi-detached dwelling, located within the CA. The terms of Section 72 of the Planning (Listed Buildings and Conservation Areas) Act 1990 require me to pay special attention to the desirability of preserving or enhancing the character or appearance of the CA.

Taken together Policies BE1 and HE1 of the London Borough of Hillingdon Local Plan, Part 1, [name] (2012) (HLP1), DMHB1 and DMHB4 of the London Borough of Hillingdon Local Plan, Part 2, Development Management Policies (2020) (HLP2) seek to secure high quality design that safeguards local character and distinctiveness, particularly in conservation areas. These objectives are supported by Policy HC1 of The London Plan (LP) and the National Planning Policy Framework (2025) (‘the Framework’).

The Harlington Village Conservation Area Appraisal (2015) (CAA) identifies that, as a well-preserved inter-war house, the appeal property makes a positive contribution to the CA. It also indicates that the removal of chimney stacks and overly large or inappropriately designed roof extensions are both issues which detract from the character and appearance of the CA.

The proposed rear dormer would extend across almost the entire width of the extended roof plane and would rise to the main ridge height. In view of this excessive scale and bulk, particularly when viewed in conjunction with the massing of the proposed hip-to-gable extension, the proposed scheme would not appear subservient to the host dwelling. Instead, it would be a disproportionate, top-heavy addition that would unacceptably harm the architectural balance of the original house.

Furthermore, the proposed hip to gable roof extension would necessitate the removal of two side chimneys. These chimneys are a characteristic feature of homes in the line of properties on this part of [address]. [name] recognise that some chimneys have already been removed, many remain and these are integral to the character of the host building. Their removal, combined with the overall works to the roof profile, would result in the unacceptable loss of the original roof form.

I acknowledge the appellant’s intention to use materials that match the existing dwelling. However, this would not sufficiently mitigate the harm arising from inappropriate scale and massing I have identified.

The appellant points to a similar gable roof extension and dormer to the adjoining property, No [address]. He considers that the appeal scheme would reinstate symmetry and balance between this pair of semi-detached homes. However, that existing extension serves to highlight the harm that overly large roof extensions can cause to the CA. Moreover, the Council indicates that the alterations to No 12 resulted from unauthorised works which became lawful through the passage of time. Consequently, I have attached limited weight to this example in considering the appeal. A previous planning breach does not justify the repetition of a harmful design.

I also recognise that properties on [address] benefit from rear dormer roof extensions. However, these are terraced houses which sit outside the Conservation Area and therefore have a different context to the appeal scheme. Similarly, whilst a property to the rear of the appeal site includes a mansard roof, given that it appears to be an original design feature of a larger building the circumstances of that roof are not comparable to the proposed scheme. Also, nearby properties at 7 and [address] include wrap-around dormers, these significantly vary in form and design compared to the appeal scheme. Each case must be determined on its own merits and the presence of other roof extensions or varying roof forms in the vicinity does not justify the further erosion of the CA’s character at this site.

Taking all the above into account, I conclude that the appeal scheme would fail to preserve the character and appearance of the host dwelling and CA. It would therefore conflict with the development plan and the Framework when taken as a whole.

Paragraph 215 of the Framework states that where a development proposal will lead to less than substantial harm to the significance of a designated heritage asset, this harm should be weighed against the public benefits of the proposal.

In this case, the harm identified to the Harlington Village Conservation Area, while less than substantial, is nevertheless a matter of considerable importance and weight. The public benefits of the scheme are limited, primarily consisting of the provision of additional living space for the current and future occupiers of the dwelling. [name] am mindful of the appellant’s desire to enlarge the property, these are essentially private benefits.

The Framework makes it clear that the conservation of heritage assets is a core planning principle. Private residential improvements do not carry sufficient public weight to outweigh the identified harm to the character and appearance of the Conservation Area, to which I must give great weight.

Consequently, the proposal does not represent sustainable development. It would conflict with the heritage and design objectives of HLP1 Policies BE1 and HE1, HLP2 Policies DMHB1 and DMHB4, LP Policy HC1 and the Framework. There are no material considerations, including the public benefits of the proposal, that would justify a decision other than in accordance with the development plan.

For the reasons given above and having had regard to all other matters raised, I conclude that the appeal should be dismissed.