How Much Does a Mansard Loft Conversion Cost?
A mansard loft conversion costs between £35,000 and £60,000+ in the UK — the most expensive type, but it delivers the largest usable floor space.
All prices include a free feasibility survey, structural engineering, planning checks, building regulations submission, and the full build. Our quotes are fixed-price — no hidden costs.
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Mansard Loft Conversion Price Breakdown
Typical price range
£35,000 – £60,000+
Starting from
£35,000
Typical duration
10–14 weeks
A mansard conversion creates a near-vertical rear wall with a flat or slightly pitched roof, maximising headroom across the full loft floor area. It is the most spacious type of conversion and is particularly popular for mid-terrace and end-of-terrace properties in urban areas.
The price range above covers the full project — including your structural engineer, all building materials, labour, and building regulations sign-off. We provide fully itemised quotes so you know exactly what you are paying for.
What Affects the Cost?
Loft Size
Floor area and ridge height directly affect material and labour costs. Larger lofts cost more but add proportionally more value.
Roof Pitch
Steeper pitches provide more natural headroom and are generally cheaper to convert. Shallow pitches may require more structural work.
Structural Work
Some conversions require steel beams, new joists, or party wall agreements. These add cost but are included in our fixed-price quotes.
Specification
The quality of windows, insulation, flooring, and fixtures affects the final price. We offer a full range of specification levels.
Planning
Most conversions fall under Permitted Development. Conservation areas or Article 4 zones may need a planning application (typically £200–£500 in fees).
Location
London and South East properties typically fall at the upper end of price ranges due to higher labour costs.
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Every property is different. Get a free survey and fixed-price quote — written within 48 hours, fully itemised, no hidden costs.
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Available across London
Service details
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