Isleworth Hounslow 7 New Apartments

The Challenge

Planning Permission in Conservation Area: Securing Hounslow planning permission for backland development in the Spring Grove Conservation Area presented unique challenges. The site at 51 Thornbury Road, Isleworth sits behind existing properties, accessed via a narrow 36-metre driveway. The London Borough of Hounslow's local planning authority required careful architectural drawings demonstrating the proposed development would conserve the conservation area's character while respecting neighbours' privacy and outlook.

Backland Site Access Constraints: The narrow access created immediate concerns about vehicle movements, construction logistics and emergency vehicle access. Hounslow Council planning officers needed convincing that seven new homes could be delivered on this constrained site without harming neighbours' living conditions or creating highway safety issues.

Neighbour Objections: Six neighbour responses raised concerns during the statutory consultation period about privacy loss, overdevelopment, inadequate amenity space and construction vehicle access. Our planning application needed to address each concern through detailed architectural drawings and robust planning justification to secure Hounslow planning permission approval.

Our Approach

Pre-Application Engagement: AC Design Solution engaged with Hounslow Council's planning department through two rounds of pre-application advice before submitting the formal planning application. This iterative approach proved essential for understanding local planning authority requirements specific to this Spring Grove Conservation Area site. The first pre-application explored a three-storey mansion block which the council considered too bulky. The second addressed a revised scheme featuring semi-detached houses converted to flats—much closer to what was eventually approved.

Detailed Planning Application Drawings: We prepared comprehensive architectural drawings showing how the proposed development would integrate with the conservation area context. The approved design features traditional architectural character: two-storey building with pitched hipped roofs, central chimney, bay windows, brick facades with slate/clay roof tiles, and metal-framed windows. The design reads as two pairs of semi-detached houses connected at the centre, respecting the local vernacular found throughout Isleworth, Osterley and surrounding Hounslow areas.

Solving Access Constraints Creatively: Rather than fighting for on-site car park provision with inadequate access, we proposed a car-free development. This removed highway safety concerns and aligned with Hounslow's sustainable transport policies. Planning conditions secured pedestrian and cycle access only, a consolidated parcel drop-off point near the highway, and confirmed residents would be ineligible for parking permits.

Building Control Integration: Planning and building control are separate statutory processes. Our Fire Strategy prepared in accordance with Building Regulations Part B5 specified additional fire safety measures to compensate for emergency vehicles being unable to access the site due to the narrow driveway. We coordinated with Hounslow Building Control early to demonstrate the proposed development was deliverable, not just designable.

Addressing Statutory Consultation

Privacy and Overlooking: Our architectural drawings showed separation distances of 17-21 metres to Thornbury Road properties—in line with London Plan guidance. While tree removal would create more direct views, the distances ensured acceptable privacy levels. This satisfied Hounslow Council planning officers that neighbour amenity would be protected.

Design Quality Response: One neighbour actually praised the "attention to detail regarding style, finished and matching the local vernacular"—validation that our traditional design approach succeeded in this conservation area. This positive feedback, referenced in the case officer's report, helped demonstrate the quality of our planning application drawings.

Amenity Space Provision: Our planning application drawings demonstrated 101sqm communal amenity space, exceeding the 83sqm statutory requirement. Private balconies for first-floor flats and private gardens for ground-floor units meant all seven flats met or exceeded the Nationally Described Space Standards enforced by local authorities.

Sustainability and Carbon Reduction

80% Carbon Reduction: The proposed development achieved an 80% carbon dioxide emissions reduction against Building Regulations Part L (2022) baseline through enhanced fabric specifications, high-performance glazing, heat pump installation (no gas), seven high-output solar photovoltaic panels on south-facing roofs, and water efficiency measures (105 litres/person/day). A carbon offset payment of £3,025 secured through planning conditions addresses the remaining shortfall to net zero—a statutory requirement for new planning approvals in London under mayoral policies.

Results

Hounslow Planning Permission Granted: Hounslow Council's planning committee approved the planning application on 5th February 2026 following officer recommendation. The case officer's report concluded: "The scheme is considered to be of a high design quality, suited to the existing site and surroundings and would provide a high standard of residential accommodation. The proposal is considered to relate well to the local character and context, reflecting the location of the site."

Seven New Homes Delivered: The approved flat conversion delivers much-needed housing in Hounslow including two family-sized units while respecting the Spring Grove Conservation Area character. Ground floor provides 2 x two-bedroom flats and 1 x one-bedroom flat. First floor provides 2 x studio flats, 1 x one-bedroom flat and 1 x two-bedroom flat—a net gain of one family-sized unit compared to the demolished six-bedroom house.

Car-Free Development Approved: The decision notice confirmed no planning appeal would be required. The developer could proceed with building control submissions and construction. The car-free approach solved the constrained access problem while meeting Hounslow's sustainable transport objectives applicable across Isleworth, Osterley, Heston, Feltham and surrounding areas.

This 51 Thornbury Road project in Isleworth demonstrates how careful architectural design, detailed planning application drawings and strategic pre-application engagement with Hounslow Council can secure planning permission for backland development in conservation areas. It shows how AC Design Solution navigate complex sites where planning permission risk, access constraints and heritage conservation all need balancing.

Need Hounslow planning permission for a challenging site? Contact our CIAT Chartered Architectural Technologists at AC Design Solution to discuss planning applications, detailed architectural drawings and building regulation drawings for your project in Hounslow, Isleworth, Feltham, Brentford, Chiswick or across the London Borough of Hounslow.