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 Nicholas Carpenter12/04/2023Trustindex verifies that the original source of the review is Google. Clapham Construction have done a great job on our loft conversion and we are very pleased with how smoothly the project went, and the brilliant loft space that we now have. Paul - thank you especially for guiding us through all the stages before and during the build. Their workmen were hard working from start to finish, efficient, and obviously very skilled. They were also polite, helpful and really tidy. We had great communication by email with their office, and with Paul in person and on the WhatsApp group - thank you. Our family in USA are now looking forward to staying with us in comfort this summer and beyond!Posted on Bianca Hamilton16/03/2023Trustindex verifies that the original source of the review is Google. Paul, Dangis and the team are simply top notch. They did such a high-quality job on a tight timeframe and communicated so well throughout. They were a pleasure to work with, handled all elements of the build from start to finish and kept disruption as minimal as they could. Couldn’t recommend them more highly if I tried.Posted on Mindy Lee29/01/2023Trustindex verifies that the original source of the review is Google. Thank you Clapham Construction! Your team were friendly, efficient, and highly motivated. The project ran to schedule with effective overlapping of tasks to allow for minimum disruption. Paul kept us actively involved at each stage of the process, so we always knew what was happening when, which was really reassuring. If we ever had a question, he would talk it through with us in person and offer advice without any pressure or expectation. The work is completed to an excellent standard. All the construction workers where kind, considerate, friendly, polite and kept our house as clean and tidy as possible. This took so much of the stress out of living on site during the works with a young son. Even the neighbours commented on how polite and considerate the builders had been. We would highly recommend this team for anyone thinking of undertaking a loft conversion in the future.Posted on Shayan Bokhari29/12/2022Trustindex verifies that the original source of the review is Google. Paul, Dangis and their team were excellent given we had some obstacles with the council on design, they accommodated what we required. The work was very professional and communication was on point. We are very happy with our end result and any teething issues they resolved quickl. I would recommend the team to anyone. Thanks again for all your hard work.Posted on Laila A29/12/2022Trustindex verifies that the original source of the review is Google. Really lovely team - all professional, friendly and was great to have Dangis and Paul popping in regularly and being on the ball with the project. Happy with our new loft, all work done to an excellence standard, any follow up questions or issues dealt with quickly. Would highly recommend. Thank you very much.Posted on Dani Carter25/10/2022Trustindex verifies that the original source of the review is Google. Absolute professionals is the first thing that comes to mind when I think of Clapham Construction service. And there are two further things you need to know about them: they are brilliant at what they do and they are generous in spirit. Throughout our project Paul and Dangis answered our naive questions with warmth and care. They helped guide us at every turn, and almost certainly saved us money by making sure we considered all the options we had before making key decisions. But not just customer care, the building work is also top notch. The build itself was a well oiled process, coordinated with skill. I was initially worried about getting an anonymous loft company I'd never heard of in (after getting 8 different quotes from a variety of places including famous local ones) and being part of the 'box on the roof' brigade. Yet somehow, they have created build magic with some tweaks on 'a little bit of height' here, and 'a little configuration' there. We keep marvelling at the sturdiness and smoothness of the physical build even now, and the army of highly skilled teams they have were a pleasure to host in the house while we worked from home. And finally the most important bit - the money stuff- our Loft extension (including bathroom) was completed on time and more or less on budget. The additional costs were the unforseen - (yikes a victorian chimney needs dismantling!) and a few flourishes that we ourselves added to the mix - (can the door handles be gold?). Any additional build costs were communicated efficiently and immediately. Our experience of Clapham Construction is that they are patient, hugely knowledgable, and detail orientated with a wealth of incredible advice. Don't delay on getting them on your project!Posted on Mikey Johns22/09/2022Trustindex verifies that the original source of the review is Google. We spoke to a few companies to quote our dormer loft conversion but were immediately impressed speaking to Dangis & Paul and went with Clapham CS. We’re really happy with the end result which has given us some much needed extra space. Progress was quick, these guys are very experienced and know exactly what they’re doing. They’ll talk you through your plans and give you honest advice at key stages when you need to make a decision, very patient with us too! Would definitely recommend, they’ve done numerous houses in our neighbouring streets too, end results always look great.Posted on Maria Luisa McKendry18/09/2022Trustindex verifies that the original source of the review is Google. Highly recommend this company. As first time buyers and first time renovators we couldn't be happier with their service. Paul and Dangis are very professional and thorough, at no times does it feel like corners are cut. They are able to provide genuine advice and guidance while being accommodating ensuring a stress free process.Posted on Stuart Williams18/09/2022Trustindex verifies that the original source of the review is Google. Clapham Construction completed our kitchen extension for us. We’re really pleased with the results, and it has changed the whole place. The price was agreed upfront and there were no hidden extras. Good communication throughout the whole process on WhatsApp and Dan showed great building experience. They had the whole team from build, kitchen fitting through to finishing the garden off available in house so made it a lot easier. Thanks guys.Posted on Tom Forman05/09/2022Trustindex verifies that the original source of the review is Google. We are delighted with our new loft conversion, Clapham Construction did a great job. They were highly professional, no hidden costs, and with friendly employees who treated the rest of the house with respect. We would not hesitate to recommend them.Google rating score: 5.0 of 5, based on 54 reviews

