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 rebuilds the rear of your roof as a near-vertical wall topped with a flat or gently pitched roof. This shape gives you full headroom right across the loft floor, not just down the middle. As a result, it is the most spacious conversion type we offer. It is especially popular for mid-terrace and end-of-terrace homes in busy urban areas, where every extra square metre matters.
The price range above covers the full project. That means your structural engineer, all building materials, the labour, and building regulations sign-off are already accounted for. We then itemise every line in your fixed-price quote, so you know exactly what each pound is paying for. As a result, there are no grey areas and no costs that appear halfway through the build.
What Affects the Cost?
Six main factors move a mansard loft conversion up or down within the range above: loft size, roof pitch, structural work, specification, planning, and location. The good news is that we account for every one of them during your free survey, before any price is fixed. Here is how each factor plays out in practice.
Loft Size
Floor area and ridge height drive material and labour costs. Larger lofts cost more, but they add proportionally more value, so the spend usually pays you back.
Roof Pitch
A steeper pitch gives you more natural headroom and is generally cheaper to convert. A shallow pitch, by contrast, often needs extra structural work to gain that height.
Structural Work
Some conversions need steel beams, new joists, or a party wall agreement. These add to the cost, but we always include them in your fixed-price quote so nothing surprises you later.
Specification
The quality of your windows, insulation, flooring, and fixtures shapes the final price. We offer a full range of specification levels, from solid and practical to fully high-end.
Planning
Most conversions fall under Permitted Development, so no application is needed. However, conservation areas or Article 4 zones may require planning permission, which typically costs £200–£500 in fees.
Location
London and the South East usually sit at the upper end of the price ranges. That premium reflects the higher labour costs across the region.
Get an Exact Price
Every property is different, so the only way to be precise is to look at yours. Book a free survey and we'll send a fixed-price quote within 48 hours. It is fully itemised, with no hidden costs.
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Available across London
Service details
Get Your Fixed-Price Mansard Loft Conversion Quote
The survey is free and there's no obligation. We assess your property in person, then send a fully itemised written quote within 48 hours.