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%.
Price of a Loft Conversion
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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 Type | Average 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 – £70,000 | Semi-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.
Get Your Loft Converted Today
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.
View Our Design and Build Process
Check out the work of our amazing teams and what we can achieve in your home
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.
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)

Posted on Andy Brown19/02/2026Trustindex verifies that the original source of the review is Google. From the initial meeting to the final finishing touch, Paul, Dangis and their team were great! We knew exactly what to expect each week, we had lots of photos and drone videos of work happening when we couldn’t see. They were full of advice and suggestions when we couldn’t visualise the end result. They left our home as clean and as tidy as they possibly could (we were living in the house as they were working around us). We are really pleased with the end result and with the building experience! Great time, fantastic work ethic and brilliant result!Posted on Rebecca Barrett15/12/2025Trustindex verifies that the original source of the review is Google. We can’t thank Paul, Dangis, and the team, enough for their hard work on our house. The house is everything we had imagined and more. We increased our scope multiple times throughout the process, and the team helped us seamlessly, and were always there to answer questions and support our plans. We only have good things to say about Clapham Construction, and will definitely be recommending them to all our friends and family. Thanks again!Posted on Helen Stevens03/09/2025Trustindex verifies that the original source of the review is Google. I cannot speak highly enough of Clapham Construction. Paul and Dangis were a dream to work with from start to finish. Everything was communicated so well and they provided honest, transparent and clear advice throughout; I felt supported and guided through all the decisions and they helped me make more bespoke decisions such as our windows and floor which weren’t necessarily easy! Everyone who came to work on the loft was excellent and it has all been completed to a high standard. The loft is beautiful and we just can’t believe how much space we have and how well done everything is. I would (and have!) recommend to anyone! Thank you Paul and Dangis - and we will be coming straight back to you for the next project!Posted on Georgia Beales01/08/2025Trustindex verifies that the original source of the review is Google. We’ve had our dormer loft conversion for coming up to three years now and haven’t had any major issues in this time. Any minor snagging issues have been dealt with quickly by Clapham. The whole process from start to finish was seamless. All the builders were very friendly and considerate too. Will continue to recommend this company to anyone who needs a loft done and will not hesitate to use again in the future. Thank you!Posted on Danilo Rico07/07/2025Trustindex verifies that the original source of the review is Google. Clapham construction service was extremely professional, the project was finished before the plan and we are so happy with our new space. Problems were resolved quickly and efficiently throughout the process. This was one of our best investment that not only added value to our property but also a significant improve of our quality of life.Posted on Joel Prime02/07/2025Trustindex verifies that the original source of the review is Google. I had a loft conversion completed by Clapham Construction Service earlier this year and couldn't be happier with the results. Paul and Dangis were on site every day and kept me fully informed throughout the entire process. Their communication, professionalism, and attention to detail were outstanding. I felt completely confident in their work from start to finish. Highly recommended for anyone looking for reliable and high-quality building services.Posted on Jane Ansell08/05/2025Trustindex verifies that the original source of the review is Google. We recently completed a double mansard loft conversion with Clapham Construction Service, and were very happy with the whole design and build process from start to finish. Paul and Dangis were great to work with, providing clear communication and always being available to answer questions or discuss options. Their team are also excellent, with all the trades doing a great job, very professional and respectful of the rest of our house. Inevitably with a build project there were a couple of issues that cropped up along the way, but CCS were excellent at helping resolve them. We are delighted with the final loft and the extra space, and have already recommended them to others!Posted on Jamie Garratt24/01/2025Trustindex verifies that the original source of the review is Google. We have just completed a loft conversion with Clapham Construction and it was great! We are so pleased with the new loft we have in our house, but the process of working with CC was really good. They were easy to engage with from the outset, the price was competitive and the actual construction was quick and efficient. Obviously it was a major building project with all the mess and decisions you’d expect, but it was made a lot easier and less stressful working with Paul, Dangis and the team. They completed the project on time and on budget and we enjoyed working with them - that is more than almost anyone we know can say about similar projects! We’d definitely recommend them.Posted on Christina Ansong16/10/2024Trustindex verifies that the original source of the review is Google. We had an exceptional experience with Clapham Construction for our loft conversion. Paul, Dangis, and the whole team were fantastic from start to finish. They transformed our attic into two beautiful loft rooms and a bathroom, exceeding our expectations with their attention to detail. The entire project was completed at an impressive speed without compromising quality. The team showed great care throughout, ensuring everything was done to the highest standard. Their service was professional, friendly, and stress-free. We’re absolutely thrilled with the results and would highly recommend Clapham Construction!Posted on Ayan Sengupta31/08/2024Trustindex verifies that the original source of the review is Google. We have recently used Clapham Construction Services for loft conversion to add a bedroom and a bath in the house. We are very happy with the end-to-end experience with Paul, Dangis and the entire CCS team for high quality work done in quick time and with a very collaborative approach. Our overall project went into some unexpected blockers, but Paul and Dangis patiently helped us to resolve all the matters, kept us updated with timely communication and have been very flexible to guide us. They brought in a fantastic team to complete the work fast and in a cost-efficient manner. We will recommend CCS any day as a trusted team for home transformation projects.Google rating score: 5.0 of 5, based on 83 reviews


