Basement & Ground Extension Bowerdean SW6 

The Project in Brief

Services: Planning application, structural engineering, building regulation drawings, and party wall notices and awards — all delivered as a single coordinated programme for a multi-element Conservation Area scheme in the London Borough of Hammersmith and Fulham.

Four Elements, One Coordinated Scheme

45 Bowerdean Street is a Victorian terraced property in Fulham, SW6, within a designated Conservation Area. The scope of work covered four distinct elements. A second floor rear extension built over part of the existing back addition. Demolition of the existing ground floor extensions and replacement with a new single-storey side and rear extension. Excavation of the rear garden and beneath the existing building footprint to enlarge the basement and form a rear lightwell. And alterations to the roof of the ground floor side extension to incorporate new rooflights.

Each element had its own design, structural and regulatory demands. Delivering all four simultaneously — without version conflicts or information falling between consultants — required every discipline to be managed under one roof from day one.

Planning in a Conservation Area

The application was assessed against the Hammersmith and Fulham Local Plan (2018), the Planning Guidance SPD (2018), and the National Planning Policy Framework (2024). Conservation Area designation means any alteration must be of a form, nature and scale that is sensitive and compatible with the character of the area. The design has to earn its approval — not just avoid refusal.

The planning officer was satisfied the proposal met this test in full. The decision records that the scheme would not cause unacceptable harm to neighbouring amenity, would be of an acceptable visual appearance, and that its form and scale were compatible with the Conservation Area. Permission was granted under delegated authority on 9 April 2026, application reference 2026/00378/FUL.

The materials were fixed and submitted as part of the application: aluminium doors at ground and lower ground floor, brick to match the existing on all walls, slate to match the existing roof on the pod extension, and timber-framed windows throughout. All were approved as submitted. No revisions were requested by the officer during the application.

Basement Enlargement and Lightwell

Basement works in Hammersmith and Fulham are assessed against Key Principles BL1, BL2 and BL3 of the Planning Guidance SPD (2018). The Council applies detailed requirements to how lightwells are designed and how they meet the surrounding ground level. The approved scheme requires the rear lightwell to be fitted with walk-on glass set flush with the surrounding ground, with no railings or vertical elements permitted around it. The basement is conditioned for use only as part of the single dwellinghouse and cannot become a house in multiple occupation.

The flood risk implications of excavating in this part of Fulham required a formal Flood Risk Assessment, coordinated and submitted as part of the planning package. The assessment, dated 23 March 2026, was approved as submitted. All flood prevention and mitigation measures must be installed before any part of the development is occupied. The structural and assessment work that underpins schemes of this type is covered in detail on our basement impact assessments page.

Structural Engineering

The structural scope on this project was substantial. Basement enlargement and rear excavation required retaining wall design, an underpinning strategy and load redistribution as the existing ground floor extensions came down. The second floor rear extension over the back addition required beam sizing and connection details to transfer new loads through to the structure below. The replacement ground floor extension required a full structural design for the new roof and wall construction.

All structural calculations were coordinated with the architectural drawing package from first issue. When the structural engineer and the architectural technologist are working in the same practice on the same project, the drawings and calculations are consistent from the start. Building control receives a coherent submission — not a package that needs reconciling across separate consultants. Our residential structural work is delivered by our in-house house structural engineers.

Building Regulation Drawings

Full building regulation drawing packages were produced for the scheme, covering structural, thermal, fire safety, drainage and ventilation requirements under the relevant approved documents. For a project of this scale — basement excavation, new retaining construction, a second floor rear addition and a replacement ground floor extension all proceeding at the same time — the submission needed to be comprehensive and internally consistent, with no gaps for building control to follow up.

The flood mitigation requirements from the approved Flood Risk Assessment were built into the building regulation drawings from the outset, so the planning conditions and the technical package told the same story from day one.

Party Wall Surveying

Works of this scope trigger obligations under the Party Wall etc. Act 1996 across multiple boundaries. Basement excavation, demolition of existing extensions and new construction at ground and second floor level all engage the party wall provisions in relation to adjoining owners. The party wall team served the required notices, managed neighbour engagement and secured the awards needed for the build to proceed.

Running party wall surveying in-house alongside planning, structural and building regulation work means notices are served at the right point in the programme. There is no delay waiting for a separate surveyor to be brought up to speed on a scheme they had no part in designing. Our party wall surveyors are members of the Institute of Party Wall Surveyors (IPWS) and the Faculty of Party Wall Surveyors (FPWS).

Pre-Commencement Conditions

Two conditions in this permission require action before work can start. Where piling is proposed, a Piling Method Statement must be submitted to and approved by the Council in consultation with Thames Water before any piling takes place — standard practice for basement schemes in inner London given the proximity to underground sewerage infrastructure. The flood mitigation condition requires all measures from the approved Flood Risk Assessment to be installed before any part of the development is occupied.

Knowing which conditions are pre-commencement and which are pre-occupation matters for programming. A missed discharge requirement can hold up groundworks and add real cost. Identifying these obligations at the outset means the contractor programme accounts for them from the beginning, not after the first site meeting.

The Result

Planning permission was granted under delegated authority on 9 April 2026. The scheme was approved as submitted — materials confirmed as specified, no design changes required, no revisions during the application. Structural engineering, building regulation drawings and party wall surveying were all delivered within the same programme, coordinated by the same team that produced the planning drawings.

AC Design Solution's architectural services are delivered by CIAT Chartered Architectural Technologists and structural engineers who have completed over 10,000 UK projects. If you have a basement, extension or Conservation Area project in Hammersmith and Fulham, Kensington and Chelsea, Westminster, or anywhere across London, get in touch to discuss what you need.