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Price of a Loft Conversion

The average price of a loft conversion in London in 2025 is between £50,000 and £90,000, depending on the project’s size, type, and final specifications. Factors like adding a bathroom, the type of windows, and the quality of finishes will influence the final cost. A loft conversion can increase your property’s value by up to 20%.

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Average Loft Conversion Costs in London (2025 Estimates)

These are approximate cost estimates to give you a general idea of pricing. For accurate project costing, please contact us to book a consultation and receive a detailed fixed-price quotation tailored to your specific requirements.

Conversion TypeAverage Cost Range (London)Best For
Velux / Skylight Conversion£40,000 – £50,000+Speed, budget, and projects where existing headroom is sufficient.
Dormer Conversion£50,000 – £60,000+Adding significant headroom and usable floor space; the most popular option.
Hip-to-Gable Conversion£50,000 – £70,000Semi-detached and detached homes, creating a large amount of internal space.
Mansard Conversion£60,000 – £85,000+Maximising space in terraced houses, though often requires planning permission.

For a detailed estimate tailored to your home, use our loft conversion cost calculator below

What Factors Influence the Price of a Loft Conversion?

Beyond the type of conversion, several other factors will affect the final quote:

  • Property Size & Complexity: A larger loft or a more complex roof structure will naturally increase the cost.
  • Internal Specifications: The quality of finishes for floors, windows, and doors plays a significant role.
  • Bathrooms & En-Suites: Adding plumbing and a bathroom can add £4,500 to £6,000 or more to the total cost.
  • Structural Requirements: The cost includes structural engineer fees (£500–£1,000) and necessary steel beams and floor reinforcements.
  • Professional Fees: This includes architectural design, planning applications, and building control inspections.

Key Takeaways

Average London Cost: £50,000 – £90,000+.

Value Added: Can increase property value by up to 20%.

Key Cost Factors: Conversion type, property size, and internal specifications.

Timeline: Most loft conversions complete in 10–12 weeks.

Loft Conversion Complete Process

Free online calculator estimate → No-fee on-site survey for a fixed price → Full design package (drawings, structural calcs, planning/PD) → 8-12 week build managed daily → Building-control sign-off, final clean and ten-year fixed-price guarantee.

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Is a Loft Conversion a Good Investment?

Absolutely. For London homeowners, a loft conversion is one of the most reliable ways to add value to a property. By adding a bedroom and bathroom, you not only increase your living space but can see a return on investment of up to 20%. It is often more cost-effective than moving or building a ground-floor extension.

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While our loft conversion calculator provides an excellent estimate, the next step is a detailed, no-obligation quote from one of our specialists. We will conduct a free site survey to provide you with a fixed price for your project.

Ready for an Exact, Fixed-Price Quote?

If you’d like to book a free, no-obligation consultation with one of our team members, please don’t hesitate to contact us today on 0203 950 7957. We will be more than happy to answer any questions and arrange a consultation to discuss your plans.

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Testimonials

Case Study: Custom Loft Conversion with All-Inclusive Pricing

We delivered a bespoke loft conversion tailored to Marie’s evolving needs. Our responsive, collaborative approach allowed real-time adjustments throughout the project — ensuring the final result matched expectations perfectly. The all-inclusive pricing model meant no surprises, just quality craftsmanship at excellent value. Another smooth, stress-free build completed on time and on budget.

"Had a loft conversion done which we are very pleased about. Paul and Dangis are very responsive and would literally reply to anything almost immediately! You can make any adjustments as you go and it ensures it fits what you want/were expecting.

Great thing is: everything is included in the quote so no surprises! Very well priced too — we had comparison from other companies either more expensive or similar prices but they are so nice and upfront when you meet the team that you can only choose to go with them! Thanks."
– Marie (Review via Trustpilot)
Rated Excellent on Trustpilot
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