How much does a London
loft conversion cost?
2026 prices, by type.
Velux, rear dormer, L-shape, hip-to-gable or mansard — the real figures we use on client quotes across Fulham, Battersea, Chiswick and beyond. Sixty-second calculator. No callback.
- Every figure on this page is produced by the same pricing engine as our calculator and our written estimates. Nothing here is typed in by hand.
- Outer-London base rate, VAT included, at the finish grade named in each row. Your postcode moves the figure — the zone table shows by how much.
- The engine prices a loft by floor area and finish grade, not by dormer shape, so two types at the same grade share a £/m² rate. What separates them in the table is the area each one yields and the finish the structural work typically carries.
- A band, not a quotation. We hold it to ±7% only after a measured survey — see the precision ladder below.
Pick your roof. See the price.
Every figure inclusive of design, build, site set-up, the risk allowance and VAT. The specification at each end of a range is named in the row, because a band that runs from the smallest plainest job to the largest and richest is not one product's spread.
| Type | Cost inc VAT | What it is |
|---|---|---|
| Rooflight (Velux) conversion25–30 m² · builder's finish | £54,000–£64,800£2,160/m² | The roof line does not change. New floor structure, insulation to current regs, rooflights in the existing slope, staircase and a habitable room. The cheapest loft to build — not because the rate is lower, but because nothing structural is rebuilt, so the job stays small and plainly finished. Capped by whatever head height you already have.Planning · Almost always permitted development. Building regulations still apply in full. |
| Rear dormer25–35 m² · builder's to balanced finish | £54,000–£100,800£2,160/m² – £2,880/m² | The London Victorian terrace default. The rear slope is cut away and rebuilt as a full-height wall with a flat roof over, which buys standing height across most of the floor plate.Planning · Permitted development within 40 m³ added volume on a terrace, 50 m³ on a semi or detached. |
| L-shape rear dormer32–45 m² · balanced finish | £92,160–£129,600£2,880/m² | A rear dormer that wraps over the back outrigger. More roof to rebuild, two junctions to weather, and usually enough floor area for a double bedroom plus an en-suite.Planning · Usually permitted development, but the volume allowance is the binding constraint — we check before quoting. |
| Hip-to-gable + rear dormer35–50 m² · balanced finish | £100,800–£144,000£2,880/m² | For a semi or end-of-terrace with a sloping side. The hip is demolished and rebuilt as a vertical gable, then combined with a rear dormer. The most floor area a standard roof will give up.Planning · Permitted development on most semis and end-terraces outside conservation areas. |
| Mansard38–55 m² · balanced to signature finish | £109,440–£217,800£2,880/m² – £3,960/m² | The roof is replaced rather than altered — a near-vertical new storey at about 70° with a flat top. The most floor area and the most structure, which is why it prices at the top finish grade even when the interior spec is modest.Planning · Always full planning permission. The usual answer in conservation areas where a dormer would be refused. |
Each range runs from the smallest typical job at the lower finish grade to the largest at the upper one — the specification at each end is named in the row, because a range whose ends are different products is not a range for one product.
The same finish, five sizes.
One finish grade the whole way down, so the only thing changing is floor area. This is the table to hold a competing quote against — if their per-m² figure is far below ours, something has been left out of the scope rather than out of the margin.
| Size | Floor area | Cost inc VAT | Per m² | On site |
|---|---|---|---|---|
| Small dormerOne double bedroom, no en-suite | 25 m² | £72,000 | £2,880/m² | 7 wks |
| Standard dormerDouble bedroom plus a shower room | 30 m² | £86,400 | £2,880/m² | 9 wks |
| Large dormer / L-shapeBedroom, en-suite and a study corner | 38 m² | £109,440 | £2,880/m² | 11 wks |
| Hip-to-gableTwo rooms or one suite with storage | 45 m² | £129,600 | £2,880/m² | 13 wks |
| MansardA full floor — two bedrooms and a bathroom | 55 m² | £158,400 | £2,880/m² | 16 wks |
One finish grade down the whole ladder, so the only thing changing between rows is area. The per-m² column is flat by design: our rate is per square metre, so the total scales with the size you give us and nothing else. That is the column to check a competing quote against.
The same loft, three finish grades.
Identical structure, identical roof, identical staircase compliance. What moves is the staircase material, the joinery, the tiling and the lighting — the part you can still change at design stage without touching the drawings.
Regs-compliant throughout, plainly finished. Pine stairbox staircase, painted MDF doors, standard rooflights, shower enclosure over a tray, carpet or LVT.
Engineered timber floor, hardwood-tread staircase, fitted wardrobes to one wall, tiled wet area, designed lighting circuit, underfloor heating in the en-suite.
Bespoke joinery run, hardwood staircase with a made balustrade, large-format or stone tiling, scene-controlled lighting, wall-hung sanitaryware, structural rooflights.
The same job at 30 m², three finish grades. Everything structural is identical across all three — what changes is what you touch, stand on and look at. It is the cheapest lever you have, and the one most quotes never show you.
Every stage of a 30 m² dormer, largest first.
The actual stage allocation our written estimates carry, for the typical job above. Structural carpentry and the roof lead it, which is the true shape of a loft — you are buying a new floor and a rebuilt roof, and the bedroom is what happens afterwards.
| Stage | Ex VAT | Share | |
|---|---|---|---|
| Structural carpentryD · Structural carpentry | £10,392 | 14.4% | |
| Painting & decoratingS · Painting & decorating | £7,423 | 10.3% | |
| Roof constructionF · Roof construction | £6,680 | 9.3% | |
| Plumbing & heatingP · Plumbing & heating | £5,567 | 7.7% | |
| ScaffoldingQ · Scaffolding | £5,567 | 7.7% | |
| TilingK · Tiling | £4,082 | 5.7% | |
| Bathroom installN · Bathroom install | £3,340 | 4.6% | |
| ElectricalO · Electrical | £3,340 | 4.6% | |
| Preliminaries & site setupA · Preliminaries & site setup | £2,969 | 4.1% | |
| FlooringL · Flooring | £2,969 | 4.1% | |
| Joinery 2nd fixM · Joinery 2nd fix | £2,969 | 4.1% | |
| Building control & final fixT · Building control & final fix | £2,969 | 4.1% | |
| Demolition & strip-outB · Demolition & strip-out | £2,227 | 3.1% | |
| StaircaseH · Staircase | £2,227 | 3.1% | |
| Internal partitionsI · Internal partitions | £2,227 | 3.1% | |
| Plasterboard & plasteringJ · Plasterboard & plastering | £2,227 | 3.1% | |
| Steel worksE · Steel works | £1,485 | 2.1% | |
| Fire strategyR · Fire strategy | £1,485 | 2.1% | |
| Windows & rooflights installG · Windows & rooflights install | £1,113 | 1.5% | |
| SubstructureC · Substructure | £742 | 1.0% |
This is the same stage allocation our written estimates are built from, not a set of percentages written for a web page. Every rate above is all-in: site set-up, supervision and the risk allowance sit inside the rate rather than arriving as a separate line at the bottom, and nothing is added after this except VAT.
What is always in, and what depends on your roof.
The rates we price with, at the unit we price them in. The first table is what every loft carries whether a quote itemises it or not — the fire strategy and the party wall awards are the two most often missing from a cheaper number.
Always in the job
These are not add-ons. They are in every figure quoted above, and they are listed so you can check whether a cheaper quote has left one out.
| Item | Rate inc VAT | Why |
|---|---|---|
| Structural engineer | £3,360per project | Calculations for the new floor, the steels and the dormer frame. Every loft needs them. |
| Building control | £1,800per project | Notification, inspections and the completion certificate you will need when you sell. |
| Tin-hat scaffold | £7,200per project | A temporary roof over the whole works so the house stays dry while the slope is open. |
| Fire compartmentation | £960per project | A protected escape route from the new floor to the front door. Not optional and not negotiable. |
| Party wall surveyor | £1,440per agreement | One agreement per affected neighbour. On a mid-terrace that is usually two. |
Depends on your house and your choices
Add the ones that apply. This is the part of a quote that usually arrives as a surprise, so it is published instead.
| Item | Rate inc VAT | Why |
|---|---|---|
| En-suite to the loft | £5,184per room | First and second fix plumbing for a shower room in the roof. The commonest single addition to a loft. |
| Hardwood staircase | £10,200per flight | Against a pine stairbox. On a loft the staircase is the first thing anyone sees at the top. |
| Pine stairbox staircase | £4,560per flight | The standard regs-compliant flight assumed in the base figure. |
| Structural rooflight | £4,560each | A frameless fixed light against a standard Velux — a different product, not a better version of one. |
| Standard rooflight | £1,020each | GPL MK06 is the size most rear slopes take. |
| Chimney breast removal | £2,160each | Common in a loft, and it needs gallows brackets or a steel plus building control sign-off. |
| Macerator | £1,440per room | Where the new WC sits below or too far from the existing soil stack to fall to it. |
| Shower booster pump | £691each | London mains pressure at second-floor level is frequently not enough on its own. |
| Underfloor heating | £173per m² | Plus a manifold. Worth it in a loft bathroom, rarely worth it in a loft bedroom. |
| Acoustic stud wall | £288per m² | Rockwool plus double SoundBloc where the new room sits over a bedroom. |
| Fitted joinery | £2,640per linear m | Eaves storage and wardrobes built to the slope — the only way to use the low edges of a loft. |
| Asbestos survey | £600per project | On anything built or altered before 2000. Cheaper than finding out mid-strip. |
These are the rates we price with, at the unit we price them in. Add the ones that apply to your house and you will land within a few thousand pounds of our written estimate before you have spoken to anybody.
The same loft, four London build zones.
Access, parking suspensions, permit costs and the labour premium of working in central London. This is a build factor, not a property-value one.
| Zone | Build factor | Same 30 m² job | Where |
|---|---|---|---|
| Outer London | ×1.00 | £86,400 | Bromley, Croydon, Enfield, Kingston, Twickenham |
| Inner London | ×1.10 | £95,040 | Chiswick W4, Hammersmith W6, Clapham SW4, Wandsworth SW18 |
| Prime | ×1.20 | £103,680 | Fulham SW6, Battersea SW11, Notting Hill W11, Islington N1 |
| Prime central | ×1.40 | £120,960 | Chelsea SW3, Belgravia SW1, Kensington W8, Hampstead NW3 |
This is a build-cost factor, not a property-value one — access, parking, ULEZ, permit costs and the labour premium of working in central London. Property values rise far more steeply between these zones than build costs do, which is why a central London project usually shows the better return despite costing more to build.
What is not settled until the drawings are.
A loft has one unknown that genuinely cannot be seen from the ground, and it is the roof structure itself. The rest are decisions rather than discoveries — but they are decisions with a deadline.
Existing roof structure
A trussed roof needs more steel than a cut roof. We can usually tell from the loft hatch; occasionally we cannot.
Head height and floor build-up
This is the measurement that decides whether you have a conversion, a roof raise or a mansard. We take it before quoting, not after.
Staircase position
The most common reason a loft layout changes between first sketch and planning drawing.
Sanitaryware, tiles and brassware
Supply is a provisional sum against your choices. The fitting cost does not move; the fittings do.
Planning outcome
A conservation area or an Article 4 direction removes PD entirely, which changes what can be built before it changes what it costs.
Party wall awards
One agreement per affected neighbour, and the fees are yours rather than theirs. Budget for two on a mid-terrace.
None of these carries a figure here, and that is deliberate. We work to a contract plus variations, every variation is priced and agreed before the work happens, and a site risk allowance is already inside the rates above. Putting an invented allowance against an unknown would make the total look more settled than it is.
How accurate is a number from a web page?
As accurate as what you have told us. A figure from a size bracket is a starting point rather than a quotation, and we would rather label it than let you find out at tender.
| Accuracy | What we know | Why it narrows |
|---|---|---|
| ±20%Ballpark | Project type and a size bracket | A starting point. Useful for deciding whether to keep reading. |
| ±14%Good estimate | A measured floor area | Your actual area instead of a bracket — the single biggest improvement available. |
| ±10%Sharp estimate | Postcode and finish level | Your build zone and the specification you actually want. |
| ±7%Survey-grade | Scope answered at a measured survey | Room count, drainage, structure and access seen rather than assumed. |
The rungs are cumulative — a postcode cannot sharpen a guessed floor area, because the area is the number the rate multiplies. ±7% is a statement about that set of answers, not a promise that the figure cannot move. We work to a contract plus variations, and every variation is costed and agreed with you before the work happens rather than after.
Most London loft conversions don’t need planning.
Here’s how to tell.
Permitted development (PD)
Covers most rear dormers and hip-to-gable conversions in non-protected areas, provided you stay within 40 m³ added volume (terrace) or 50 m³ (semi/detached), don’t raise the ridge, and use matching materials. We’ll check your address before quoting.
Best for: standard Victorian rear dormers outside conservation areas.
Full planning permission
Required for all mansards, all conservation areas, all Article 4 zones, anything over PD volume limits, and anything that materially changes the front roofline. Worth the time — opens up far better design.
Best for: mansards, period houses in SW3/SW6/W11, premium specifications.
Building regulations
Even when you don’t need planning, you always need building regulations sign-off — fire escape route, staircase headroom (2m minimum), structural calcs, thermal insulation to current standards.
Required for: every loft conversion, full stop.
The 2026 London Loft Cost Guide.
Twenty-four pages of real cost data from our client lofts across SW6, SW3, W11, SW11 and W4. Straight to your inbox.
- ✓Velux, dormer, L-shape, hip-to-gable & mansard side by side
- ✓Dormer cost breakdown, line by line
- ✓Borough multipliers — Zone 1 vs Zone 2 vs Zone 3
- ✓PD vs full planning — the volume calculations explained
- ✓Building regs essentials (headroom, fire escape, stairs)
- ✓How to maximise property value uplift on a London loft
Send me the guide.
What homeowners ask us before they book.
Is an attic conversion cost the same as a loft conversion cost?
Yes. Attic conversion, loft extension and loft conversion are three names for one job — turning unused roof space into a habitable room — so the prices below apply whichever term you searched for. "Loft conversion" is what the trade, Building Control and your drawings will call it.
How much does a loft conversion cost in London in 2026?
Inclusive of design, build, site set-up, the risk allowance and VAT, at outer-London rates: rooflight (velux) conversion £54,000–£64,800 at 25–30 m² · builder's finish; rear dormer £54,000–£100,800 at 25–35 m² · builder's to balanced finish; l-shape rear dormer £92,160–£129,600 at 32–45 m² · balanced finish; hip-to-gable + rear dormer £100,800–£144,000 at 35–50 m² · balanced finish; mansard £109,440–£217,800 at 38–55 m² · balanced to signature finish. Your postcode, the finish level and the structural route move you within those. Every figure comes from the same engine as our written estimates.
What's the cost per m² for a London loft conversion?
£2,160 to £3,960 per m² including VAT, at outer-London rates. The rate is set by the finish grade rather than by the dormer shape — a mansard and a rear dormer at the same specification price at the same £/m², and the mansard costs more because it yields more floor area and usually carries a higher finish. Postcode moves it too: prime central London is +40% on build cost.
Do I need planning permission for a loft conversion?
Most London loft conversions fall under permitted development (PD): rear dormers and hip-to-gable conversions are usually allowed without planning if you stay within 40m³ added volume (terrace) or 50m³ (semi/detached), don't raise the ridge, and match existing materials. Mansards always need full planning permission. Conservation areas and Article 4 directions remove PD rights entirely.
How long does a loft conversion take?
Allow 6–10 weeks for design and planning (longer for mansards), then 8–14 weeks on site for a standard dormer, 12–18 weeks for an L-shape or hip-to-gable, and 14–20 weeks for a mansard. Most of the work is external — your house stays liveable throughout except for the final week when the staircase goes in.
Will a loft conversion add value to my London house?
Usually, and the honest answer is that it depends on your street rather than on a national average. A loft adds habitable floor area, and floor area is what London property is priced on — so the question worth asking is what a comparable house with an extra bedroom has recently sold for within a few streets of you. We will not quote you a percentage: we have no source for one that would still be true of your address, and a number we cannot show you the working for is not worth reading. What we can tell you is the build cost, to ±7% after a survey, which is the half of that sum you can actually control.
What's the minimum head height I need to convert my loft?
You need at least 2.2–2.4m head height from the existing ceiling joists to the underside of the ridge for a meaningful conversion. Less than that and you're looking at a roof raise (which loses PD rights) or a mansard. We measure on the free site visit — most Victorian and Edwardian London houses have enough.
Will my neighbours have a say? What about party wall?
If you're building on or near the boundary line, or cutting into a shared party wall to insert steels, you need a Party Wall Award under the 1996 Act. We serve notice on your behalf and the typical timeline is 4–8 weeks. Each neighbour appoints their own surveyor — fees usually £1,000–£3,000 per agreement and are your cost.
Can I stay in the house during the build?
Yes, almost always. Loft conversions are predominantly external works — scaffolding goes up, the roof is opened from above, and the staircase is installed last. You'll have a noisy fortnight when the dormer is framed and a dusty week when the stairs go in, but you don't need to move out.
Loft conversion cost in 60 London areas.
Twenty minutes with Nick Elias RIBA.
On us.
Bring your floorplan or roof photo. Walk out with a feasibility verdict (head height, PD vs planning, structural route), realistic budget and a programme — even if a loft isn’t the right move for your house.
Studio at 20 Dawes Road SW6, video call, or on site.
A real studio, in Fulham.
One company, one address, one registered number — not a lead form that sells your details on. You can walk into the office on Dawes Road and ask for Vladimir by name.
One number. Sixty seconds. No callback.
Price your loft using the same 2026 rate card we quote real clients with.
Price my loft →The home you actually want, finished on the date in the contract — and you watch every day of it happen from your phone.
- Your number in 60 seconds
- Itemised stage breakdown in 2 minutes
- Survey within 7 days
You answer 3 questions. We do the drawings, planning, party wall, trades and snagging.
- 10% to mobilise, then weekly against work already done — with 5% held past handover: 2.5% released at practical completion and 2.5% at the end of the 12-month defects period
- £550 survey fee credited in full against your contract
- Every variation priced and signed before a penny is spent
The date is a term of the contract. We finish on the agreed date, or we pay you £500 for every week we are late.
4.8 from 16 Google reviews
Every review is published in full on our reviews page, including the one-star. Google is the only platform we quote a rating for, because it is the only one we can evidence.
As a structural engineer, I've collaborated with 2VP Projects Ltd on several residential projects in London. Their attention to detail, proactive site management, and clear communication make every stage—from design to execution—smooth and efficient. It's rare to find a contractor who values both precision and professionalism at this level. A truly reliable partner.
Great company to work with. Professional, reliable and easy to deal with. Vladimir and the team are always responsive, straightforward and genuinely care about doing things properly. I've had a very positive experience working with 2VP and would happily recommend them.
Extension went smoothly from start to finish. Communication was great throughout, and the team delivered exactly what we asked for. Thank you, 2VP!
What is covered, and by whom
A builder’s own guarantee is worth exactly as much as the company standing behind it. Here is what comes as standard, what you can add, and what has to come from somebody other than us — set out in full on our insurance and guarantee page.
- 12-month workmanship warranty on second-fix fittings
- £5M public liability
- £10M employer's liability
- £2M professional indemnity
- HomePro insurance-backed guarantee, 10 years
- Priced at 2.5% of the contract sum
- Underwritten by an insurer, so it survives us
- 10-year structural warranty on a new dwelling (NHBC / LABC / Premier)
- Professional fees — architect, engineer, building control
- We will tell you when you need one rather than let you find out