Cost guide · 2026
LoftConversionCostWestLondon2026
2026 loft conversion pricing for West London boroughs — Ealing, Hounslow, Hammersmith & Fulham, Brent, Harrow, Richmond, Kensington & Chelsea. Edwardian semis, prime conservation overlays, and the most expensive prime postcodes in the city.
Quick answer
A loft conversion in West London costs £50,000–£160,000 in 2026. Velux from £50,000; dormers £62,000–£95,000; L-shape dormers £85,000–£125,000; mansards £100,000–£160,000. Kensington & Chelsea and parts of Hammersmith carry the highest premiums — conservation, listed buildings and access surcharges. Outer Hounslow, Ealing and Harrow are more competitive. Cost per m² is £2,400–£3,600.
What moves the price
The seven cost factors that matter most.
Kensington, Chelsea, Holland Park, Notting Hill, Brook Green, Brackenbury — listed buildings common, planning often refused on first round.
Chiswick, Ealing, Brondesbury, Harrow on the Hill — generous ridge heights, L-shape dormers and mansards both feasible.
Parsons Green, Munster Village, Fulham Broadway — mid-terrace Victorian and Edwardian; mansards typical at £105–135k.
Pitshanger, North Ealing, Hanwell, Greenford — hip-to-gable + dormer at the £78–98k mark.
Parts of Hammersmith, Notting Hill, Chiswick, Bedford Park — full planning required even where PD would normally apply.
Hounslow (TW3-TW8), Harrow (HA1-HA9), Greenford (UB6) — easier access and lower trade rates, 10–18% below inner West.
K&C, prime Hammersmith — premium glazing, hand-built joinery, MVHR are baseline; £125–160k typical for mansard with full spec.
Cost breakdown
Where the money actually goes.
Percentage breakdown of a typical mid-spec project. Add or subtract per your finish tier.
| Line item | % of total | £ on avg project |
|---|---|---|
| Structure (steels, floor, roof) | 11% | £11,550 |
| Insulation & weatherproofing | 9% | £9,450 |
| Windows & glazing | 8% | £8,400 |
| First fix MEP | 11% | £11,550 |
| Plaster & decoration | 8% | £8,400 |
| Stairs & joinery | 9% | £9,450 |
| Bathroom (if ensuite) | 8% | £8,400 |
| Flooring & finishes | 5% | £5,250 |
| Lighting & second fix | 5% | £5,250 |
| Fees & approvals | 12% | £12,600 |
| Site management & plant | 10% | £10,500 |
| Margin & contingency | 4% | £4,200 |
Real projects
Worked examples from completed builds.
London zones
Where your borough sits in the price band.
| Zone | Multiplier | Notes |
|---|---|---|
| Prime (SW3, SW10, W8, W11) | 1.20–1.35× | Chelsea, South Ken, Kensington, Notting Hill — listed common |
| Inner West (W2, W4, W6, W12, W14, SW6) | 1.10–1.20× | Paddington, Chiswick, Hammersmith, Shepherds Bush, Fulham |
| Mid West (W3, W5, W7, W9, W10, W13, NW6, NW10) | 1.00–1.10× | Acton, Ealing, Hanwell, Maida Vale, Brent |
| Outer West (TW3-TW10, HA1-HA9, UB1-UB8) | 0.90–1.00× | Hounslow, Harrow, Hillingdon — semi-detached stock |
Builderr vs other London builders.
The construction industry has a wide distribution of operators. Here's what changes between a directly-employed, fixed-scope outfit and the alternatives.
| Criterion | Builderr | Typical London builder | Cowboy outfit |
|---|---|---|---|
| Labour model | Directly employed team (PAYE) | Mixed subcontract gangs | Day-rate cash labour |
| Pricing | Fixed-scope itemised quote | Estimate + provisional sums | Verbal price + variations |
| Design & engineering | In-house architect + SE | Outsourced, separate billing | Builder draws on the back of an envelope |
| Planning + LDC handled | Yes — included in price | Often charged extra | Builder asks you to apply |
| Party wall surveyors | Instructed by us | Your responsibility | Skipped (illegal) |
| Building control | Plans + site inspections booked by us | Building Notice route | Not registered |
| Project management | Dedicated PM, weekly photo updates | Foreman doubles up | Owner-manager juggles 5 jobs |
| Payment schedule | Stage payments against signed-off milestones | Weekly invoices | Cash up front |
| Insurance | £10M PL + 10yr structural warranty | £2–5M PL only | No documented cover |
| Snags at handover | <3 typical | 20–30 typical | Walk-off mid-job common |
| Variation creep | 0% — fixed scope | +15–25% over original quote | +40%+ regularly |
Save £21,000–£47,250 on a loft conversions.
Industry data (FMB, RICS, Which? Trusted Trader 2024) shows the average London construction project overruns by 18–22% on cost and 25–35% on time. Fixed-scope contracts with a single accountable team eliminate that variance. The savings above assume a typical project at £105,000.
Related
See the full loft conversions service page.
FAQ
Loft Conversion Cost West London:
common questions.
How much does a loft conversion cost in West London?
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A West London loft conversion costs £50,000–£160,000. Edwardian semis in Ealing, Chiswick and Brondesbury run £80,000–£105,000 for a dormer. Mansards on Hammersmith terraces £105,000–£140,000. Prime Kensington & Chelsea projects with bespoke joinery and premium spec reach £140,000–£160,000+. Outer Hounslow and Harrow are 10–18% below inner West.
Why are Kensington & Chelsea loft conversions so expensive?
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K&C combines several premium factors: extensive conservation areas (Chelsea, South Kensington, Brompton, Earl's Court, Holland Park), high concentration of listed buildings, narrow streets with parking restrictions and welfare surcharges, premium spec expectations (hand-built joinery, MVHR, smart systems), and trade rates 20–30% above outer London. A mansard with full prime spec typically runs £140,000–£160,000, and listed building consent adds 12–20 weeks to the planning timeline.
Which West London borough is cheapest for a loft conversion?
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Outer Hounslow (TW3, TW4, TW5, TW7) and outer Harrow (HA2, HA3, HA4, HA7) are the most cost-efficient. Lower trade rates, easier vehicle access, mostly 1930s and post-war semi stock that suits hip-to-gable + dormer, and minimal conservation pressure. Typical loft conversion £75,000–£95,000 with ensuite vs £100,000+ for the same project in inner West.
Do I need planning permission for a loft conversion in Hammersmith & Fulham?
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Often yes. H&F has 47 conservation areas including Bedford Park, Brackenbury Village, Brook Green and Munster Village. Article 4 directions remove PD rights in parts of W6, W12 and SW6. Full planning is required for mansards, conservation areas and listed buildings. We confirm the planning route at the free desk-based assessment before quoting.
Are Edwardian semis in Ealing good for loft conversions?
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Yes — Edwardian semis in Pitshanger, North Ealing, Hanwell and Brentham have generous ridge heights (often 7m+ to ridge) and good roof spans, making them well-suited to L-shape dormers or full mansards without raising the ridge line. Typical dormer £80,000–£105,000 with ensuite; L-shape £100,000–£125,000. Many are permitted development outside conservation areas.
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