Loft Conversion Cost Calculator — UK Prices 2025
Loft Conversion Cost Calculator
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Adds ~20% to labour
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How much does loft conversion cost in the UK?
Use our calculator above to get an accurate estimate based on your specific requirements. Prices are based on real quotes from UK tradespeople and updated quarterly.
What affects the cost of loft conversion?
- Location: London and the South East are 15–40% more expensive than the national average.
- Size and complexity: Larger or more complex jobs cost proportionally more.
- Material quality: Budget, mid-range and premium specifications can vary by 2–3x.
- Time of year: Demand peaks in spring and summer — book in winter for better availability and pricing.
- Access: Difficult access (scaffolding, confined spaces) adds to labour costs.
How to save money on loft conversion
- Get at least 3 quotes from different tradespeople.
- Book during quieter periods (January–March for most trades).
- Be flexible on start dates — tradespeople often discount for convenient scheduling.
- Supply your own materials where possible (but confirm with your tradesperson first).
- Combine jobs — having multiple trades on site at once can reduce overall costs.
How to find a good tradesperson
Always check reviews on Checkatrade, Rated People or MyBuilder. Ask for references from recent similar jobs. Ensure they are appropriately qualified and insured. Never pay the full amount upfront — a deposit of 10–25% is standard.
Frequently asked questions
How much does a loft conversion cost in the UK?
A Velux loft conversion costs £20,000–£30,000. A dormer conversion costs £35,000–£60,000. A hip-to-gable conversion costs £40,000–£65,000. A mansard conversion costs £50,000–£90,000. Prices vary significantly by region, with London adding 30–40%.
Do I need planning permission for a loft conversion?
Most loft conversions fall under permitted development and do not require planning permission. However, mansard conversions, properties in conservation areas, and conversions that exceed permitted development limits will need planning permission.
How long does a loft conversion take?
A Velux conversion takes 4–6 weeks. A dormer conversion takes 8–12 weeks. A mansard conversion can take 12–16 weeks. This includes structural work, insulation, plastering, and electrics.
Does a loft conversion add value to my home?
Yes. A loft conversion typically adds 15–25% to a property's value. In London and the South East, the return on investment is often 100%+ due to high property prices.
What is the minimum head height for a loft conversion?
You need a minimum of 2.2m from the floor to the highest point of the roof ridge for a viable loft conversion. Measure from the top of the ceiling joist to the underside of the ridge board.