Loft Conversion and Extension Cost Guide

IN Guides
Construction Costs Loft Conversion and Extension Cost Guide

The amount you pay to build your loft conversion or extension varies on the type of build and features you require. At the time of publishing this guide June 2017, we would offer the following prices as a guide per square meter. Please note that these prices exclude VAT and fees.

Cost per Loft Conversion type


Velux Conversion (per m2)

£1,200 -   £1,500

Dormer Conversion (per m2)

£1,680 -   £2,400

Mansard Conversion (per m2)

£1,800 -   £2,600


Cost per Extension type


Single Storey extension (per m2

£1,500 -   £2,000

Two Storey extension (per m2)    

£2,250 -   £3,000


Building Works Costs



£10,000 - £15,000


£4,500 -   £11,000

New Boiler

£1,800 -   £3,500

Underfloor Heating (per m2)


Radiators (per m2)


Decorating (per m2)


Flooring (per m2)