How much do extensions and loft conversions cost?
Guide prices for every project we build, including VAT where it applies.
Most single-storey extensions cost about £2,600 to £4,000 per square metre including VAT, two-storey extensions £2,400 to £3,850, loft conversions £30,000 to £110,000 depending on type, and garage conversions £12,000 to £54,000. These are 2026 guide ranges; every project is priced on survey and fixed in writing.
Extensions
Single-storey extensions
| Single-storey extensions | Guide price incl. VAT |
|---|---|
| Standard specification | £2,600 to £3,000 per m² |
| Good specification | £3,000 to £3,500 per m² |
| High specification | £3,500 to £4,000 per m² |
Unit: per m² of new floor area. Guide ranges only; your price is fixed in writing after the survey.
Double-storey extensions
| Double-storey extensions | Guide price incl. VAT |
|---|---|
| Standard specification | £2,400 to £2,900 per m² |
| Good specification | £2,900 to £3,400 per m² |
| High specification | £3,400 to £3,850 per m² |
Unit: per m² of new floor area. Guide ranges only; your price is fixed in writing after the survey.
Side return extensions
| Side return extensions | Guide price incl. VAT |
|---|---|
| Standard specification | £3,350 to £3,700 per m² |
| Good specification | £3,700 to £4,150 per m² |
| High specification | £4,150 to £4,550 per m² |
Unit: per m² of new floor area. Guide ranges only; your price is fixed in writing after the survey.
Wraparound extensions
| Wraparound extensions | Guide price incl. VAT |
|---|---|
| Standard specification | £3,400 to £3,800 per m² |
| Good specification | £3,800 to £4,250 per m² |
| High specification | £4,250 to £4,700 per m² |
Unit: per m² of new floor area. Guide ranges only; your price is fixed in writing after the survey.
Kitchen extensions
| Kitchen extensions | Guide price incl. VAT |
|---|---|
| Extension build | £2,600 to £4,000 per m² |
| Kitchen supply and fit, mid-range | £10,000 to £20,000 |
| Kitchen supply and fit, high-end | £20,000 to £40,000 |
Unit: build per m², plus the kitchen. Guide ranges only; your price is fixed in writing after the survey.
Orangeries
| Orangeries | Guide price incl. VAT |
|---|---|
| Standard specification | £3,000 to £3,500 per m² |
| Good specification | £3,500 to £4,100 per m² |
| High specification | £4,100 to £4,800 per m² |
Unit: per m² of floor area. Guide ranges only; your price is fixed in writing after the survey.
Porches
| Porches | Guide price incl. VAT |
|---|---|
| Open canopy over the door | £2,500 to £5,000 |
| Brick porch with tiled roof | £6,000 to £10,000 |
| Larger porch or front extension | £10,000 to £16,000 |
Unit: per porch. Guide ranges only; your price is fixed in writing after the survey.
Garden annexes
| Garden annexes | Guide price incl. VAT |
|---|---|
| Standard specification | £2,400 to £2,900 per m² |
| Good specification | £2,900 to £3,400 per m² |
| High specification | £3,400 to £3,900 per m² |
Unit: per m² of floor area. Guide ranges only; your price is fixed in writing after the survey.
Lofts and upward extensions
Loft conversions
| Loft conversions | Guide price incl. VAT |
|---|---|
| Rooflight conversion | £30,000 to £45,000 |
| Dormer conversion | £50,000 to £90,000 |
| Hip-to-gable with dormer | £60,000 to £95,000 |
| Mansard conversion | £65,000 to £110,000 |
Unit: per conversion. Guide ranges only; your price is fixed in writing after the survey.
Dormer loft conversions
| Dormer loft conversions | Guide price incl. VAT |
|---|---|
| Rear dormer, bedroom only | £50,000 to £65,000 |
| Full-width dormer with en-suite | £60,000 to £80,000 |
| L-shaped dormer (over rear outrigger) | £65,000 to £90,000 |
Unit: per conversion. Guide ranges only; your price is fixed in writing after the survey.
Hip-to-gable loft conversions
| Hip-to-gable loft conversions | Guide price incl. VAT |
|---|---|
| Hip-to-gable with rear dormer | £60,000 to £80,000 |
| Double hip-to-gable (detached house) | £70,000 to £95,000 |
Unit: per conversion. Guide ranges only; your price is fixed in writing after the survey.
Mansard loft conversions
| Mansard loft conversions | Guide price incl. VAT |
|---|---|
| Rear mansard | £65,000 to £85,000 |
| Front and rear (double) mansard | £80,000 to £110,000 |
Unit: per conversion. Guide ranges only; your price is fixed in writing after the survey.
Bungalow and upward extensions
| Bungalow and upward extensions | Guide price incl. VAT |
|---|---|
| Chalet conversion with dormers (total) | £45,000 to £85,000 |
| New first floor, standard specification | £2,200 to £2,800 per m² |
| New first floor, good specification | £2,800 to £3,300 per m² |
| New first floor, high specification | £3,300 to £3,800 per m² |
Unit: per m² of new floor area. Guide ranges only; your price is fixed in writing after the survey.
Conversions
Garage conversions
| Garage conversions | Guide price incl. VAT |
|---|---|
| Single integral garage | £12,000 to £17,000 |
| Single attached garage | £12,000 to £24,000 |
| Single detached garage | £18,000 to £30,000 |
| Double garage | £25,000 to £54,000 |
Unit: per garage. Guide ranges only; your price is fixed in writing after the survey.
Basement and cellar conversions
| Basement and cellar conversions | Guide price incl. VAT |
|---|---|
| Existing cellar conversion | £1,900 to £3,000 per m² |
| New basement excavation | £4,200 to £6,600 per m² |
Unit: per m² of floor area. Guide ranges only; your price is fixed in writing after the survey.
House-to-flat conversions
Priced on survey. Costs depend heavily on the house, the number of flats and how much existing structure can stay. We price each conversion on survey and set out every element in writing. Qualifying conversions that change the number of dwellings can benefit from the reduced 5% VAT rate.
New builds and renovation
New-build homes
| New-build homes | Guide price |
|---|---|
| Standard specification | £2,000 to £2,500 per m² |
| Good specification | £2,500 to £3,000 per m² |
| High specification | £3,000 to £3,600 per m² |
Unit: per m² of floor area (VAT zero-rated where it qualifies). Guide ranges only; your price is fixed in writing after the survey.
Knock down and rebuild
| Knock down and rebuild | Guide price |
|---|---|
| Demolition and site clearance (total) | £15,000 to £35,000 |
| Rebuild, standard specification (per m²) | £2,100 to £2,600 per m² |
| Rebuild, good specification (per m²) | £2,600 to £3,100 per m² |
| Rebuild, high specification (per m²) | £3,100 to £3,700 per m² |
Unit: per m² rebuild (VAT zero-rated where it qualifies), plus demolition. Guide ranges only; your price is fixed in writing after the survey.
House renovations
| House renovations | Guide price incl. VAT |
|---|---|
| Light refurbishment | £600 to £1,000 per m² |
| Full renovation | £1,000 to £1,800 per m² |
| Structural renovation and remodel | £1,800 to £2,800 per m² |
Unit: per m² of floor area. Guide ranges only; your price is fixed in writing after the survey.
Structural alterations
| Structural alterations | Guide price incl. VAT |
|---|---|
| Single load-bearing wall removal with steel | £3,000 to £7,500 |
| Chimney breast removal with support | £1,800 to £4,500 |
| Multiple walls or full open-plan remodel | £8,000 to £20,000 |
Unit: per job. Guide ranges only; your price is fixed in writing after the survey.
Re-roofing
| Re-roofing | Guide price incl. VAT |
|---|---|
| Terraced house | £6,000 to £10,000 |
| Semi-detached house | £8,000 to £15,000 |
| Detached house | £12,000 to £25,000 |
Unit: per roof. Guide ranges only; your price is fixed in writing after the survey.
Design, kitchens and bathrooms
Architectural design and planning
| Architectural design and planning | Guide price incl. VAT |
|---|---|
| Measured survey and existing drawings | £500 to £1,200 |
| Planning drawings and application | £1,200 to £3,000 |
| Building regulations drawings and specification | £1,000 to £2,500 |
| Structural calculations | £500 to £2,000 |
Unit: per stage. Guide ranges only; your price is fixed in writing after the survey.
Kitchen installation
| Kitchen installation | Guide price incl. VAT |
|---|---|
| Fit only (your units) | £3,000 to £7,000 |
| Supply and fit, mid-range | £10,000 to £20,000 |
| Supply and fit, high-end | £20,000 to £40,000 |
Unit: per kitchen. Guide ranges only; your price is fixed in writing after the survey.
Bathrooms and en-suites
| Bathrooms and en-suites | Guide price incl. VAT |
|---|---|
| En-suite or shower room | £5,500 to £10,000 |
| Family bathroom refit | £7,000 to £12,000 |
| Premium bathroom or wet room | £12,000 to £20,000 |
Unit: per room. Guide ranges only; your price is fixed in writing after the survey.
What is not included in these prices?
Council planning and building control fees, party wall surveyor fees, and anything you choose to supply yourself, such as a kitchen bought separately. Your written quote lists exactly what is and is not included.
Guide prices were last reviewed on 25 October 2026 against published 2026 UK cost guides and include VAT at 20% where it applies. New-build and replacement-dwelling figures assume zero-rated VAT where the work qualifies.