Mansard Loft Conversion Cost UK 2026

A mansard conversion changes the whole roof slope to near-vertical, maximising headroom and floor area. It's the gold standard for Victorian terraces in London, but the most expensive type at £55,000–£95,000 in 2026.

Quick answer

Typical UK price range: £55,000–£110,000. Typical time: 10–12 weeks.

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Loft conversion calculator

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Loft conversion type Velux / rooflight Dormer Hip-to-gable Mansard L-shaped

Loft floor area (m²)

Region London South East South West Midlands North of England Scotland Wales Northern Ireland

Specification level Basic / standard Mid-range Premium / high-end

Extras

En-suite bathroom £8,000–£12,000 Extra Velux windows £1,500–£1,500 Underfloor heating £2,500–£4,500 New staircase £1,800–£3,500 Walk-in wardrobe £1,500–£3,500

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Estimate only. Prices reflect 2026 UK market data — get quotes from local tradespeople for accurate pricing.

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Budget Under £5,000 £5,000 – £15,000 £15,000 – £30,000 £30,000 – £60,000 £60,000+ Not sure

Timeline As soon as possible 1 – 3 months 3 – 6 months 6+ months Just researching

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Key points

• Adds the most floor area of any conversion type
• Always needs planning permission (changes the roof shape from the street)
• £2,000–£2,800 per m² — premium for the masonry work
• Most common in central London terraces and conservation areas

Cost breakdown

Item	Low	High
Mansard structure (masonry)	£18,000	£32,000
Slate or zinc roofing	£6,000	£12,000
Internal finishing	£8,000	£14,000
Staircase + flooring	£4,000	£7,500
Architect + planning + building control	£4,500	£8,500

Cost by UK region

Region	Typical cost
London	£111,375
South East	£103,125
South West	£90,750
Midlands	£82,500
North England	£74,250
Scotland	£78,375
Wales	£74,250

How to save money

• Allow 12–16 weeks for planning before you even start on site
• Use slate or zinc for a mansard — concrete tile looks wrong
• Mansards add 25–35 % to property value in London terraces

How to find a trusted tradesperson

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• Checkatrade
• MyBuilder
• Bark

FAQs

Do I need planning for a mansard?

Yes — mansards always need planning permission because they change the roof line. Conservation areas and Article 4 directions make this more involved.

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Disclaimer: Prices are guide ranges based on 2026 UK market data. Get quotes from local tradespeople for accurate pricing.