Loft conversions · Portsmouth

How much does Loft conversions cost in Portsmouth? (2026 price guide)

A basic roof-light loft conversion typically costs £30,000-£45,000, while a more involved dormer conversion usually runs £45,000-£65,000, and larger hip-to-gable or mansard conversions can reach £70,000-£100,000 or more. Adding an en-suite bathroom typically adds a further £6,000-£10,000 to the total.

Price is driven mainly by the type of conversion, roof structure and pitch, the number of windows or dormers added, insulation and structural requirements, and whether planning permission is needed rather than permitted development rights. Converting older roof structures often costs more due to additional strengthening work.

Choosing a specialist loft conversion company rather than a general builder can streamline structural calculations and building control sign-off, potentially saving time and reducing costly design changes mid-project.

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