Running out of rooms? Maybe the kids are sharing, your home office is the kitchen table, and moving in London now costs £60,000+ in fees alone. However, the answer is sitting right above your head. Specifically, a well-built loft conversion turns dead roof space into a proper bedroom, en suite or studio — and typically adds 20–25% to your property value (see our full cost guide). Furthermore, our team has been building them across West London and Surrey for over 15 years.
London houses come in many shapes, and not every conversion type suits every property. For example, a rooflight on a roof without enough headroom wastes money — in contrast, a mansard on a 1970s semi makes no architectural sense. Here is how each option works and who it is right for. To estimate your own project budget, try our free loft conversion calculator.
Dormer conversions extend vertically from your existing roof slope, creating a box of full-height usable space. Generally speaking, this is the most popular type across London because it produces a proper-feeling bedroom on almost any terraced or semi-detached house.
With a Velux conversion, the work stays within the existing roofline — therefore no structural changes to the roof shape are needed. Typically, this is the quickest and cheapest route, provided your existing headroom is already at least 2.3 metres.
Where hip-to-gable applies, this rebuilds the sloping hip side of your roof as a vertical gable wall, which dramatically increases usable floor area and headroom. As a result, it is the go-to option for semi-detached and end-of-terrace homes across Ealing, Hounslow and Hillingdon.
Mansards restructure the entire rear roof slope into near-vertical walls topped by a flat roof — effectively adding a full new storey. Specifically, this option produces the largest possible floor area and the most refined finish. However, planning permission is almost always required.
Not sure which type fits your home? The simplest way to start is by matching your property type to the typical recommendation. Of course, every house is different, so we confirm the right approach during the free survey.
| Your Property | Best-Fit Conversion | Why |
|---|---|---|
| Victorian Terrace Pre-1900, cut timber roof |
Rear Dormer or Mansard | Steep roof pitch suits a dormer; mansards add the most space in conservation areas. |
| Edwardian Semi 1900–1918 |
Hip-to-Gable + Rear Dormer | The hip end is the limiter — squaring it off unlocks significant floor space. |
| 1930s Semi Hipped roof, deep eaves |
Hip-to-Gable + Rear Dormer | Typically the highest-value conversion on this house type — adds a true second floor. |
| 1960s–80s Semi Trussed roof structure |
Dormer (Trussed) | Truss roofs need structural redesign — costs slightly more, but very achievable. |
| Bungalow | Full Conversion | Effectively adds a whole upper floor — often requires significant roof modification. |
| End-of-Terrace | Side Dormer or Hip-to-Gable | The side-facing slope creates extra space most terraces cannot access. |
Although we work across all London boroughs, the bulk of our projects sit in West London and the borders of Surrey. Consequently, we know the planning departments, the typical roof structures and the on-street logistics for these areas inside out.
Essentially our home patch. In fact, we deliver more projects here than anywhere else — predominantly 1930s and 1950s semis with hipped roofs. As a result, hip-to-gable conversions dominate, often combined with a rear dormer.
You'll find a mix of Victorian terraces in Hanwell and Edwardian semis around Pitshanger and Northfields. Notably, parts of Ealing fall within conservation areas, so we always check planning constraints before quoting.
This borough is heavy on 1930s semi-detached stock around Hounslow Heath, Lampton and Isleworth. Therefore, hip-to-gable combinations dominate. In addition, we manage flight-path noise considerations on roof insulation specification.
Expect period properties throughout — many in conservation areas. Consequently, mansard and dormer conversions are common, and planning takes longer. Typically, we factor an extra 6–8 weeks into the Richmond timeline.
These areas have strong stock of inter-war semis and post-war detached homes. In contrast to inner-London terraces, such properties usually offer easier access and shorter build times.
Beyond West London, we also regularly work across these boroughs and the Surrey commuter belt. Therefore, our standard catchment runs right out — call us to confirm coverage for your postcode.
West London is built on Victorian and Edwardian housing stock. Importantly, those roofs were constructed using cut-timber methods that no longer match what builders typically work with today. Furthermore, each roof is slightly different — hand-built by carpenters over a hundred years ago.
As a result, two things matter when you convert one. First, the structural assessment has to be done by an engineer who understands period construction. Second, the building methods used to alter the roof must respect what is already there. Otherwise, you end up with sagging ridge lines and cracking ceilings on the floor below. For period homes in conservation areas, see our loft conversion planning permission guide.
Typically, London loft conversions run 15–25% higher than the UK average due to labour rates, access logistics and parking. The table below shows current 2026 ranges. Importantly, all prices include structural works, insulation, electrics and standard finishes. In addition, we provide fixed-price written contracts after every free survey.
| Conversion Type | Typical Cost | Build Time | Planning |
|---|---|---|---|
| Velux / Rooflight Conversion | £30,000 – £45,000 | 6–8 weeks | Permitted Development |
| Dormer Conversion | £50,000 – £75,000 | 8–12 weeks | Usually PD |
| Hip-to-Gable Conversion | £55,000 – £85,000 | 10–14 weeks | Usually PD |
| Hip-to-Gable + Rear Dormer | £70,000 – £95,000 | 12–16 weeks | Usually PD |
| Mansard Conversion | £70,000 – £120,000+ | 12–16 weeks | Planning Required |
| En Suite Bathroom (add-on) | £8,000 – £18,000 | + 2–3 weeks | Included in build |
| Loft Staircase | £3,000 – £8,000 | Included | Part of build regs |
Indicative ranges for London 2026. For a detailed regional and per-m² breakdown, see our full loft conversion cost guide, use our free cost calculator, or explore all our construction calculators.
Every project we deliver follows the same six stages. Consequently, you always know what is happening next — and there are no surprises in scope, timing or cost.
Firstly, our project manager visits your home, measures available headroom, checks structural integrity, and confirms which conversion type suits the property. In addition, the visit takes around 45 minutes and there is no obligation.
Next, our architectural team prepares full drawings and structural calculations. Furthermore, we handle the Lawful Development Certificate or full planning application — whichever your project requires.
Once design is signed off, you receive a written contract covering every element of the build. Importantly, the agreed price never changes during the project unless you request a change yourself.
Our team then installs floor joists, steel beams, roof alterations and the dormer or mansard structure. Meanwhile, the building control inspector visits at key stages to confirm regulations compliance.
Insulation, staircase, first-fix electrical and plumbing all go in before plasterboard. As a result, the room is fully wired, plumbed and insulated before any finishing work begins.
Finally, the building inspector issues your completion certificate. Then we walk through the finished space with you, resolve any snagging, and hand over your written workmanship guarantee.
A fixed-price contract only protects you if you know exactly what it covers. Therefore, here is what sits inside our standard quote — and what you should budget for separately.
Most loft conversion disputes come from the same handful of warning signs at the quoting stage. Therefore, knowing what to watch for can save you tens of thousands and months of stress.
Usually, this means missing scope or substandard materials. Furthermore, the builder plans to come back with "variation" costs once work has started — and you have no easy way to refuse.
For example, a single-page quote with one number is not a contract. Therefore, walk away unless every element of the build is listed and priced separately in writing.
Specifically, any builder asking for more than 10–15% before materials are on site is a serious concern. In contrast, reputable companies stage payments against work completed, not in advance.
Building regulations sign-off is non-negotiable. Importantly, an unsigned loft conversion creates major problems when you sell — and is technically illegal.
In contrast, the best results come from in-house teams. Notably, builders who subcontract structural, electrical and plastering work to different firms struggle to coordinate, and quality varies stage to stage.
Always check Companies House and ask for previous project addresses you can drive past. Consequently, you can verify the work was completed and is still standing.
Specifically, here are three recent West London projects — showing the property type, the conversion approach, the rough cost band and the result. For more examples, visit our portfolio.
This Victorian end-of-terrace came with a steep slate roof. In short, the owners wanted a master bedroom plus en suite to free up the smaller rooms for their two children.
Therefore, we built a rear dormer with two front-slope Velux windows, finished with reclaimed brick on the dormer cheeks to match the house. Importantly, the project ran under Permitted Development with a Lawful Development Certificate filed for the owners' records.
In this case, we worked on a 1930s semi with a classic hipped roof. Specifically, the original loft was usable but cramped — 1.9m headroom at the centre and rapidly sloping eaves.
By squaring off the hip end and adding a full-width rear dormer, we created a master bedroom, en suite and storage area. As a result, the finished space added 32 m² and an estate agent valuation uplift of around £145,000.
For this Edwardian mid-terrace in a Richmond conservation area, full planning was indeed required — with strict conditions on slate matching, dormer setbacks and window styling.
Therefore, our planning consultant managed the full application including heritage statement and pre-app advice. Ultimately, the completed mansard added a master suite plus a separate study — effectively a full additional storey.
Our project manager will visit your property, check suitability, advise on the best conversion type and tell you exactly what the project would cost. Alternatively, get an instant estimate with our free loft conversion calculator.
Contact us today to discuss your project and receive a no-obligation quote.
