How much does a UK house extension cost per m²?

Single-storey extensions in 2026 typically cost £2,000–£3,000 per m² outside London and £2,800–£4,000 per m² in London and the South East, depending on spec, glazing and finishes.

Do I need planning permission for an extension?

Many single-storey rear extensions fall under Permitted Development, but two-storey extensions, side returns, anything in a conservation area or affecting a listed building usually needs full planning permission.

How much value does an extension add?

A well-built extension typically adds 10–20% to a UK property's value, though in price-capped markets the uplift may not exceed the build cost — always check comparable sold prices in your postcode first.

How long does a loft conversion take?

A standard dormer loft conversion takes 6–10 weeks on site. Hip-to-gable and mansard conversions take longer (10–14 weeks) due to additional structural work.

Do I need an architect or can a builder design it?

Small Permitted Development extensions can be designed by an experienced builder or a draughtsperson (£800–£2,000). Larger or planning-sensitive projects benefit from an architect or architectural technologist (£3,000–£8,000+).

Extensions & Conversions

Loft conversions, single and double storey extensions, outdoor works and major home improvements pricing.

Planning a wider project? Cross-reference bathroom renovation pricing, kitchen renovation pricing, boiler and heating costs and tradesperson day rates on the UK cost reference hub.

Loft conversion cost in the UK

Typical: £30,000–£75,000 · typical UK loft conversion

UK loft conversion costs: £30,000–£75,000 typical. Velux, dormer, hip-to-gable and mansard breakdown with labour, materials and hidden costs.

House extension cost in the UK

Typical: £30,000–£120,000 · typical UK extension

UK house extension costs: £1,800–£3,200 per m² typical. Single, double storey, side-return and wrap-around pricing with labour vs materials breakdown.

Roof repair cost in the UK

Typical: £150–£3,000 · typical roof repair

UK roof repair costs: £150–£3,000 typical. Tile replacement, leak repair, flashing, ridge tile and full re-roof pricing with labour breakdown.

Loft conversion cost breakdown in the UK

Typical: £30,000–£75,000 · dormer conversion

Detailed UK loft conversion cost breakdown: structural work 30%, roofing 15%, stairs 10%, electrics 8%, plumbing 8%, finishes 20% and fees 9%. Line-item tables.

Extension cost per m² in the UK

Typical: £1,500–£4,500 · per m²

UK extension cost per m²: £1,500–£2,500 for single storey, £2,000–£3,500 for double storey. Build cost, professional fees, VAT and location factors.

Cost of building a garage in the UK

Typical: £12,000–£40,000 · garage

How much does it cost to build a garage in the UK? Single garage £12,000–£25,000; double garage £20,000–£40,000. Prefab, brick, timber frame and detached options.

Driveway installation cost in the UK

Typical: £3,000–£15,000 · typical driveway

How much does a new driveway cost in the UK? Tarmac £50–£80/m²; block paving £80–£120/m²; resin £70–£100/m². Excavation, base, materials and labour breakdown.

Fencing installation cost in the UK

Typical: £40–£110 · per metre

How much does fencing cost in the UK? Close-board £60–£100/m; panel £40–£70/m; hit-and-miss £70–£110/m. Posts, gravel boards, labour and gates included.

Garden landscaping cost in the UK

Typical: £3,000–£50,000 · typical garden

How much does garden landscaping cost in the UK? Basic £3,000–£8,000; mid-range £8,000–£20,000; premium £20,000–£50,000+. Design, hardscape, planting, lighting and drainage.

Cost of new windows in the UK

Typical: £400–£1,500 · per window

How much do new windows cost in the UK? uPVC £400–£800/window; aluminium £600–£1,200/window; timber £800–£1,500/window. Installation, glazing options and property size factors.

Double glazing installation cost in the UK

Typical: £400–£1,000 · per window

UK double glazing costs: £400–£800 per window for uPVC; £5,000–£10,000 for a full house. A-rated units, installation, guarantees and energy savings explained.

Roof replacement cost in the UK

Typical: £4,500–£20,000 · typical house

How much does a roof replacement cost in the UK? Concrete tiles £80–£120/m²; slate £120–£180/m²; flat roof £60–£100/m². Labour, scaffolding, felt and hidden costs.

Cost of damp proofing in the UK

Typical: £400–£10,000 · typical treatment

How much does damp proofing cost in the UK? DPC injection £60–£90/m; tanking £80–£130/m²; membrane systems £40–£70/m². Survey, treatment types and guarantees.

Home renovation cost estimator for the UK

Typical: £10,000–£200,000 · 3-bed house

Estimate UK home renovation costs: light refresh £10,000–£25,000; mid-range £40,000–£80,000; full renovation £100,000–£200,000+. Room-by-room breakdown with rules of thumb.

Double glazing cost

Typical: £300–£25,000 · Average uPVC double glazed window (supplied & fitted)

Double glazing cost UK 2025. Average prices per window for uPVC, aluminium and timber frames. Full house double glazing costs.

Front door replacement cost

Typical: £500–£6,000 · Average composite front door (supplied & fitted)

Front door replacement cost UK 2025. Composite, uPVC and timber door prices including fitting costs.

Bifold doors cost

Typical: £1,800–£20,000 · Average 3-panel bifold door (3m wide)

Bifold doors cost UK 2025. Average aluminium bifolding door prices per panel, including installation. Compare bifold vs sliding.

Garage conversion cost

Typical: £6,000–£50,000 · Average integral garage conversion

Garage conversion cost UK 2025. How much does it cost to convert a garage into a room? Average prices with planning rules.

Garden room cost

Typical: £5,000–£80,000 · Average fully insulated garden room

Garden room cost UK 2025. How much does a garden room cost? Insulated garden offices and garden rooms from £8,000.

Garage door cost

Typical: £400–£6,000 · Average roller garage door (single, supplied & fitted)

Garage door cost UK 2025. Compare up-and-over, roller, sectional and side-hinged garage door prices with installation costs.

Underpinning cost

Typical: £800–£50,000 · Average underpinning project (mid-terraced)

Underpinning cost UK 2025. How much does underpinning cost? Average prices for traditional underpinning and pile underpinning.

Wall removal cost

Typical: £800–£10,000 · Average load-bearing wall removal with RSJ

Wall removal cost UK 2025. How much does it cost to knock down a wall? Load-bearing wall removal costs including RSJ steel beam.

Roof repair cost

Typical: £100–£5,000 · Average minor roof repair

Roof repair cost UK 2025. How much does it cost to repair a roof? Average prices for tile replacement, flashing repair, and leak repair.

Velux window cost

Typical: £600–£5,000 · Average Velux window installed (78x98cm)

Velux window cost UK 2025. How much does a Velux window cost to install? Average prices for supply and fitting, by size and type.

Staircase cost

Typical: £1,500–£30,000 · Average new timber staircase (straight)

Staircase cost UK 2025. How much does a new staircase cost? Average prices for timber, glass balustrade and floating staircase designs.

Skylight installation cost

Typical: £600–£12,000 · Average flat roof skylight / rooflight installed

Skylight installation cost UK 2025. How much does a skylight cost? Fixed rooflights, lanterns and opening skylights with installation prices.

Damp proofing cost

Typical: £60–£12,000 · Average rising damp treatment (mid-terrace)

Damp proofing cost UK 2025. How much does damp proofing cost? Rising damp treatment, chemical DPC, and damp survey prices.

Asbestos removal cost

Typical: £80–£15,000 · Average asbestos cement garage roof removal

Asbestos removal cost UK 2025. How much does asbestos removal cost? Licensed removal prices for roof, garage and textured coatings.

Swimming pool cost

Typical: £5,000–£200,000 · Average in-ground concrete pool installed

Swimming pool cost UK 2025. How much does a swimming pool cost? In-ground and above-ground pool prices for UK gardens.

Loft boarding cost

Typical: £400–£4,000 · Average loft boarding (partial, 3 bed house)

Loft boarding cost UK 2025. How much does it cost to board a loft? Average prices for raised loft boarding including loft ladders and lights.

External cladding cost

Typical: £40–£30,000 · Average composite cladding supply and fit (per m²)

External cladding cost UK 2025. How much does external cladding cost per m²? Timber, composite, aluminium and fibre cement cladding prices.

Orangery cost

Typical: £25,000–£100,000 · Average mid-range orangery installation

Orangery cost UK 2025. How much does an orangery cost? Average prices for brick and glass orangeries with lantern roofs.

Roof terrace cost

Typical: £6,000–£50,000 · Average roof terrace conversion (25m²)

Roof terrace cost UK 2025. How much does a roof terrace cost? Average prices for flat roof conversion to usable outdoor terrace.

House survey cost

Typical: £150–£2,500 · Average RICS Level 2 HomeBuyer Survey

House survey cost UK 2025. How much does a house survey cost? Valuation, RICS Level 2 (HomeBuyer) and Level 3 (Building Survey) prices.

Building regulations cost

Typical: £150–£6,000 · Average building regulations fee (extension)

Building regulations cost UK 2025. How much do building regulations cost? Application fees, structural engineer, and party wall surveyor prices.

Fire door cost

Typical: £80–£2,500 · Average FD30 fire door supply and fit

Fire door cost UK 2025. How much does a fire door cost? FD30 and FD60 fire door prices for homes and commercial properties.

Frequently asked questions — Extensions & Conversions

How much does a UK house extension cost per m²?: Single-storey extensions in 2026 typically cost £2,000–£3,000 per m² outside London and £2,800–£4,000 per m² in London and the South East, depending on spec, glazing and finishes.
Do I need planning permission for an extension?: Many single-storey rear extensions fall under Permitted Development, but two-storey extensions, side returns, anything in a conservation area or affecting a listed building usually needs full planning permission.
How much value does an extension add?: A well-built extension typically adds 10–20% to a UK property's value, though in price-capped markets the uplift may not exceed the build cost — always check comparable sold prices in your postcode first.
How long does a loft conversion take?: A standard dormer loft conversion takes 6–10 weeks on site. Hip-to-gable and mansard conversions take longer (10–14 weeks) due to additional structural work.
Do I need an architect or can a builder design it?: Small Permitted Development extensions can be designed by an experienced builder or a draughtsperson (£800–£2,000). Larger or planning-sensitive projects benefit from an architect or architectural technologist (£3,000–£8,000+).