Basement
conversions
in Hammersmith, W6
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We design and build Hammersmith basement conversions with basement excavation, cellar conversion, and underpinning for properties on Hammersmith Terrace, Upper Mall, Brook Green - structural engineering, party wall coordination, underpinning, waterproofing, drainage pumps, lightwells and full interior fit-out for period homes, townhouses and prime London properties where ground conditions, neighbour risk and sequencing need handling properly.
Basement Conversions in Hammersmith: What You Need to Know
Every basement conversion project in Hammersmith is designed to respect the Hammersmith Conservation Area and the character of riverside Georgian terraces, Victorian villas, Edwardian mansion flats. Our in-house RIBA Chartered Architects handle Hammersmith & Fulham planning applications, our chartered structural engineers specify any load-bearing work, and our directly-employed trades deliver the build under one fixed-price contract. We coordinate Building Control, Party Wall awards where needed, and all certifications through to handover.
Hammersmith has conservation area coverage in parts, so some properties will need planning permission for external changes while others may proceed under permitted development. We assess each property individually.
Our basement conversion projects in Hammersmith are delivered by our in-house team of RIBA architects, structural engineers and specialist tradespeople. Every project is managed under a single fixed-price contract with no hidden costs.
Hammersmith brings three distinct kinds of house to a basement brief. Hammersmith Terrace and Black Lion Lane carry fine Georgian riverside houses restored with conservation-led care; Brook Green offers handsome Victorian villas and family terraces; and Glenthorne Road and the streets around it add Edwardian mansion flats and conversions. The Georgian and Victorian houses give the most scope for a lower-ground level, while the flats bring shared structure and leases that complicate any dig. Near the Thames, the reading of ground conditions comes first.
Consent runs through the London Borough of Hammersmith and Fulham, whose conservation areas protect Brook Green and the historic riverside terraces; the council scrutinises external change and applies Article 4 controls. Because Hammersmith W6 ties much of its stock to the busy King Street spine, a brief has to respect both the period fabric and central-W6 logistics — getting materials in and spoil out on well-trafficked streets is planned early, and the historic frontages set firm limits on what can appear at pavement level.
On rates, converting existing space runs £750–£3,000 per square metre (over £6,000 finished); a new dig with underpinning is £2,100–£4,000 per square metre before fit-out.
Basement Conversions in Hammersmith: Applied to the Local Stock
Hammersmith sits in the London Borough of Hammersmith and Fulham, with conservation areas protecting Brook Green and the historic riverside terraces. Hammersmith and Fulham scrutinises external change in its conservation areas and applies Article 4 controls. Basement excavation / new basement — London-wide rate guidance: Excavation/underpinning: £2,100–£4,000/m² excavated area, excluding full fit-out (Ideal Home, Sept 2025).
Sources: LBHF — Conservation areas (borough list of 44 conservation areas) (2026); LBHF — Article 4 Directions (planning policy page) (2026); Basement excavation / new basement (Ideal Home basement cost guide, Sept 2025; Camden basement Article 4 Direction, accessed 2026-06) (2026)
What a Basement Conversion Involves
Digging out a basement adds a complete new storey without touching the garden or the street elevation — and it is the most engineering-led work we do. Ground conditions, foundation depths and the water table are investigated before a price is ever fixed, because below-ground surprises are expensive precisely when they are unplanned. Each project moves through four disciplines, delivered by one team under one contract.
- Excavation — the dig itself, planned around access, spoil removal logistics and temporary support of the house above
- Underpinning — foundations deepened in short, engineer-sequenced sections, with movement monitoring on your property and your neighbours’ throughout
- Waterproofing — a tanked, integral or cavity-drain system (Type A, B or C to BS 8102) selected for your site’s ground conditions, not by habit
- Fit-out — insulation, ventilation, light wells, staircase, plaster and finishes brought to the same standard as the floors above
How We Run Your Project
Below-ground work punishes improvisation, so every stage is closed out before the next one starts.
- Ground investigation — bore holes establish soil type, bearing capacity and water table before feasibility is confirmed.
- Design & consents — layout, light wells and stair position from our architects; underpinning sequence from our structural engineers; planning and any Basement Impact Assessment handled for you.
- Fixed-price contract — priced after the soil investigation, so ground conditions are our risk rather than your variation.
- Excavation & underpinning — sequenced digs and pours with live structural monitoring, never more than the engineer’s design allows at once.
- Waterproofing & shell — membrane or structural system installed and inspected before anything conceals it, with sump and pump provision where the site needs it.
- Fit-out & handover — services, finishes, building control sign-off and a certification pack at completion.
On site, expect 12–16 weeks for a cellar conversion and 16–24 weeks for a full dig-down — the curing time between underpinning sections cannot safely be compressed. Read the full basement conversion guide for waterproofing systems, ceiling heights and light-well design in depth.
The regulatory load is real: a chartered structural engineer must design and certify the underpinning methodology, and most excavations within three metres of a neighbouring building engage the Party Wall etc. Act 1996 — notices, schedules of condition and often a formal award before work can start. Many boroughs add a Basement Impact Assessment covering hydrology and construction management. Our planning guide library sets out what applies where.
Why Hampstead Renovations
Basements fail when design, engineering and waterproofing are handled by separate firms working from different assumptions. Here they sit under one roof: in-house RIBA Chartered Architects shape the space, our own structural engineers design and supervise the underpinning, and RICS surveying support through our sister company covers party wall and condition matters. Every project carries £10M public liability cover, a genuinely fixed price agreed after ground investigation, and a 10-year structural and waterproofing warranty. Send an enquiry before 2pm on a weekday and you will hear back from us that same day.
Basement Conversions in Hammersmith: Questions
What kind of Hammersmith properties suit a basement conversion?
The area offers three quite different types. Hammersmith Terrace and Black Lion Lane carry fine Georgian riverside houses; Brook Green brings handsome Victorian villas and family terraces; and Glenthorne Road and the surrounding streets add Edwardian mansion flats and conversions. The Georgian and Victorian houses give the clearest scope for a lower-ground level, while the mansion flats bring shared structure and leases that make a dig more complex.
How does Hammersmith & Fulham control basements in W6?
Through conservation-area scrutiny. Hammersmith sits in the London Borough of Hammersmith and Fulham, with conservation areas protecting Brook Green and the historic riverside terraces, and the council scrutinises external change in those areas while applying Article 4 controls. A basement is assessed on how its lightwells and any front-area works sit within that protected character, so the conservation case is prepared alongside the structural one.
Do the riverside houses raise particular issues for basements?
They do. The fine Georgian houses on Hammersmith Terrace and Black Lion Lane sit close to the Thames and are restored with careful, conservation-led detail, so any excavation there has to weigh ground conditions near the river alongside the heritage of the fabric above. Proximity to water makes the reading of the ground the first task, and the historic frontages set strict limits on what can appear at street level.
What does a basement conversion cost in Hammersmith?
The structural route decides it. Converting existing below-ground space is guided at £750–£3,000 per square metre of converted area, and beyond £6,000 per square metre when fully finished. A new excavation with underpinning is the larger figure at £2,100–£4,000 per square metre of dug area, before fit-out. Central-W6 logistics around King Street and the busy main roads can add to the access cost on tighter sites.
How do central Hammersmith logistics affect the works?
They matter more here than in the quieter suburbs. Hammersmith W6 mixes Victorian terraces, Edwardian facades and mansion flats with streets tied to King Street, so a refurbishment or basement brief has to respect both the period fabric and busy central-W6 logistics. Getting materials in and spoil out on constrained, well-trafficked streets is planned early, and it is a real part of the programme rather than a footnote.
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