Contents
Extensions: Cost Reference 2026
- **Single-storey rear extension:**
- •3m × 4m (12m²): £35,000–£55,000 (basic to mid)
- •4m × 5m (20m²): £55,000–£85,000
- •5m × 5.5m (27.5m²): £70,000–£115,000
- •Cost per m²: £1,600–£3,200 depending on specification and glazing
- **Side return extension:**
- •1.2m × 6m (7.2m²): £35,000–£60,000
- •Cost per m²: £4,000–£8,000 (high cost per m² due to fixed costs spread over a small area)
- **Wraparound extension (rear + side return):**
- •Typical: £75,000–£140,000
- •Cost per m²: £1,800–£3,000
- **Double storey rear extension:**
- •Small (2.5m × 3.5m footprint): £65,000–£90,000
- •Standard (3.5m × 4.5m footprint): £90,000–£140,000
- •Cost per m² (gross both floors): £1,800–£2,600
- **Key cost drivers for extensions:**
- •Glazed roof specification (rooflights vs lantern vs full glass: +£12,000–£35,000)
- •Bifold/sliding door specification (+£3,000–£12,000 over standard)
- •Structural steel specification (dependent on span)
- •Foundation type (strip vs pile — add £8,000–£20,000 for piled foundations)
- •Party wall costs (surveyors: £1,500–£5,000 — not in build contract but must be budgeted)
- •Underfloor heating (add £4,000–£10,000)
Loft Conversions: Cost Reference 2026
- **Velux (rooflight) conversion:**
- •1 bedroom (habitable room only, no bathroom): £18,000–£28,000
- •1 bedroom + en-suite (building works only, no tiles or sanitaryware): £25,000–£38,000
- **Rear dormer conversion:**
- •1 bedroom (habitable room only, no bathroom): £35,000–£50,000
- •1 bedroom + en-suite (building works only): £44,000–£70,000
- **L-shaped dormer:**
- •2 bedrooms (building works): £55,000–£80,000
- •2 bedrooms + bathrooms (building works): £65,000–£95,000
- **Mansard conversion:**
- •1 bedroom + en-suite (building works): £60,000–£90,000
- •With 2 bedrooms: £75,000–£110,000
- **Key cost drivers for loft conversions:**
- •Dormer cladding: EPDM (standard) vs zinc (add £4,000–£9,000) vs tiles
- •Staircase specification (standard softwood included; hardwood or glass upgrade: +£3,000–£15,000)
- •En-suite bathroom plumbing (included in above; tiles and suite client-supplied)
- •Structural floor specification (LVL beams — engineered timber vs standard cut timber)
- •Party wall: almost always required in London (add £1,500–£4,000 party wall surveyor costs)
Refurbishments: Cost Reference 2026
- **Cosmetic refurbishment (redecoration, flooring, minor repairs, no structural work):**
- •Per room: £1,500–£4,000
- •Whole 2-bed flat: £8,000–£18,000 (building works, exc. materials)
- •Whole 3-bed house: £15,000–£30,000
- **Medium refurbishment (replastering, new kitchen in existing space, new bathroom in existing space, new electrics/lighting, decoration):**
- •1-bed flat: £18,000–£35,000
- •2-bed flat: £28,000–£50,000
- •3-bed house: £40,000–£70,000
- •4-bed house: £55,000–£90,000
- **Full refurbishment (complete strip-out, new M&E throughout, structural alterations, new kitchen and bathroom, full replastering and decoration):**
- •2-bed flat (60m²): £55,000–£90,000
- •3-bed house (95m²): £85,000–£140,000
- •4-bed house (130m²): £110,000–£180,000
- •5-bed house (160m²): £140,000–£230,000
- **Key cost drivers for refurbishments:**
- •M&E upgrade extent (partial vs full rewire and replumb)
- •Structural alterations (each structural opening: add £5,000–£15,000)
- •Plastering extent (partial vs full)
- •Ceiling heights (higher ceilings require more scaffolding and material)
- •Listed or Conservation Area requirements
Kitchens and Bathrooms: Building Works Cost Reference 2026
- **Kitchen renovation (building works only — units, worktops and appliances are client-supplied):**
- •Cosmetic (new units in same position, minor electrical/plumbing adjustment): £4,000–£8,000
- •Medium (some layout change, new electrical circuits, new plumbing connections): £8,000–£15,000
- •Full (new layout, structural opening, full replumb and rewire, new extraction route): £12,000–£22,000
- **Bathroom renovation (building works only — tiles, sanitaryware client-supplied):**
- •Small en-suite (2m²–4m²): £4,500–£8,500
- •Family bathroom (4m²–7m²): £6,000–£12,000
- •Larger bathroom (7m²–12m²): £9,000–£16,000
- •With underfloor heating: add £800–£2,000
- **Structural works — quick reference:**
- •RSJ/steel beam (residential, up to 3m span): £5,000–£9,000 (inc. SE fee, propping, installation)
- •RSJ (3m–5m span): £7,000–£13,000
- •RSJ (5m+ span): £11,000–£18,000
- •Chimney breast removal (ground floor): £3,000–£6,000
- •Chimney stack removal (full removal and re-roofing): £5,000–£10,000
- **Drainage works:**
- •New drain connection: £2,000–£5,000 (for a standard extension or new bathroom)
- •Drain camera survey: £400–£800
- •Drain repair/relining: £1,500–£5,000 depending on extent
- •Sewer build-over agreement (Thames Water): £500–£1,500 for application; additional cost if works required
Frequently Asked Questions
How much do builders charge per day in London in 2026?▼
Skilled tradespeople in London charge £250–£450 per day depending on trade and experience level. A general labourer charges £150–£220 per day. A site manager or project manager charges £350–£600 per day. These are indicative day rates — most projects are quoted on a fixed-price basis rather than day rates.
Why are building costs higher in London than the rest of the UK?▼
London building costs are 20–35% higher than the national average due to: higher skilled labour rates (driven by London wages and cost of living); more complex site conditions (party walls, Conservation Areas, London clay requiring deeper foundations, access constraints in narrow streets); higher material transport costs (congestion charges, limited material laydown space); higher specification demanded by London clients; and higher professional fees (architect, SE, party wall, planning costs).
Are these building costs inclusive of VAT?▼
No — all figures in this guide are exclusive of VAT. Standard rate VAT (20%) applies to most new building work and refurbishment. Reduced rate VAT (5%) applies to certain works on empty properties (vacant for 2+ years) and some energy-efficiency works. Always confirm the VAT treatment with your contractor before signing a contract.
Important Note
This guide is for general information only. Building regulations, planning rules, and legal requirements change regularly and vary by local authority. Always seek professional advice specific to your project and location. To talk through your own project, book a project review.
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