Prior Approval - Additional Storey

Local Council: London Borough of Hillingdon 

Appeal Result: Allowed (Prior Approval Granted) 

Description: Creation of an additional storey to a two-storey end-of-terrace dwelling under Schedule 2, Part 1, Class AA of the Town and Country Planning (General Permitted Development) Order 2015 (as amended).

Refusal Stated: The proposed development does not constitute permitted development by virtue of Schedule 2, Part 1, Class AA of the GPDO as amended. The Council refused prior approval on the following grounds: Reason for Refusal: The proposal, by reason of its siting, height, scale, bulk, and design, would fail to harmonise with the character and architectural composition of the existing property and surrounding area. It would be detrimental to the visual amenity of the street scene and harmful to the character and appearance of the surrounding area, contrary to Policy BE1 of the Hillingdon Local Plan: Part One - Strategic Policies (November 2012) and Policies DMHB 11, DMHB 12, and DMHD 1 of the Local Plan: Part Two - Development Management Policies (2020). Prior approval was refused under Condition AA.2.(3)(a)(ii). 

Background: This scheme sought to add a third storey to an end-of-terrace property in Marshall Drive, Hayes, the only two-storey dwelling in an otherwise three-storey terrace. Due to a 600mm difference in ground levels, the existing property sat visibly lower than the adjoining terrace, creating an awkward visual imbalance. The proposed additional storey would bring the property into alignment with neighbouring dwellings while optimising the use of the site to create additional family accommodation in a sustainable residential area. Hillingdon Council refused prior approval on the grounds that the increased height would break the existing ridge line, create visual disharmony, and appear incongruous within the streetscene.

At appeal, LSE demonstrated that the Council's assessment was overly rigid and failed to appreciate the established character of the area. The case presented clear evidence that the surrounding estate featured varied rooflines and staggered layouts due to topography, making height variation a characteristic design feature rather than an anomaly. LSE showed that far from creating harm, the proposal would restore visual coherence to the terrace and harmonise with the three-storey properties opposite.

By presenting a nuanced understanding of site context, topography, and streetscene character, LSE established that the Council's refusal lacked substantive planning justification and misapplied design policies to a permitted development context. The Planning Inspector agreed, concluding that the proposal would not look incongruous or out of place and would sit comfortably within the varied streetscene. Prior approval was granted, securing a successful outcome that enhanced rather than harmed the character of the area.