Loft Conversion
Specialists in Mayfair, London.
Add a room without losing your garden. Crawford Construction designs and builds loft conversions across Mayfair and London, managing everything from architectural design to building control sign-off.
Loft Conversions
Fully licensed, insured, and custom-engineered services in London.
Add a room
without losing your garden.
A well-built loft conversion is one of the most cost-effective ways to add a bedroom, en-suite or home office to an Mayfair home — without extending the footprint or sacrificing garden space. Crawford Construction designs and builds loft conversions across Mayfair and London, from light-filled rooflight rooms in Victorian terraces to full mansard conversions that create a whole new floor.
As FMB-listed Mayfair builders, we handle the entire project under one roof — feasibility, structural calculations, planning, the Party Wall process, building control and the build itself — with an itemised fixed-price quote and one named project manager from first visit to final handover. No juggling separate architects, surveyors and trades.
Which Type of Loft Conversion Is Right for Your Mayfair Home?
The right conversion depends on your roof shape, your budget, and — in Mayfair — your conservation area status. Here are the four types we build most often, with realistic 2026 costs.
Dormer loft conversion — £50,000–£65,000
The most popular choice in Mayfair. A flat-roofed dormer extends out from your rear roof slope, adding full head height and floor space — enough for a double bedroom with an ensuite. Rear dormers usually fall under planning permission (Permitted Development) outside conservation areas. Our recent project in Summertown added a double bedroom with a new dormer, Juliette balcony and ensuite bathroom to a period home.
Velux (rooflight) conversion — £45,000–£55,000
The most cost-effective option. Your roof shape stays untouched — we install Velux roof windows, insulation, flooring and a staircase. Ideal if your loft already has 2.2m+ of head height, and the least contentious option in conservation areas like Jericho and North Mayfair, since the roofline doesn't change.
Hip-to-gable conversion — £55,000–£70,000
For semi-detached and detached homes with a sloping (hipped) side roof — common in Headington, Botley and Kidlington's 1930s housing. We build the sloping side up into a vertical gable wall, dramatically increasing internal volume. Often combined with a rear dormer for maximum space.
Mansard conversion — £65,000–£75,000+
The largest transformation: the rear roof is rebuilt at a near-vertical 72° angle with a flat top, creating an almost full extra storey. Well suited to Victorian terraces in East Mayfair and Cowley, though mansards almost always require planning permission — which we manage for you.
Every Crawford loft conversion includes structural calculations and steel design, building regulations approval, fire-safety compliance, staircase design and installation, full insulation to current standards, and our 10-year workmanship guarantee — all within an itemised, fixed-price quote. We've built lofts across Mayfair from James Street in East Mayfair to Central North Mayfair's conservation streets.
Not sure which type suits your roof? Book a free loft survey — call 01865 554333.
Local Project Examples
Loft Build Seal
Guaranteed Work
10-Year insurance-backed structural warranty.
How much does a loft conversion cost in Mayfair?
Average guide price structures for different structural designs:
| Conversion Type | Typical Mayfair Cost | Best For |
|---|---|---|
| Rooflight / Velux | from ~£15,000 | Lofts with existing head height |
| Dormer | £35,000 – £55,000 | Terraces, added head height |
| Hip-to-gable (+ dormer) | £40,000 – £65,000 | Semis & detached homes |
| Mansard | up to ~£70,000 | Maximum space, period streets |
Final cost depends on structural steelwork, staircase position, insulation, whether you're adding a bathroom, and the finish you choose. Because every roof — and every Mayfair street — is different, we give a free, itemised, fixed-price quote after a site visit rather than a guess. A loft conversion can add significant value, with well-planned conversions often boosting a property's worth meaningfully.
Do I have enough head height?
This is the first thing we check. As a rule of thumb you need around 2.2m of clear height in the existing loft at the highest point, because steelwork and insulation reduce the finished ceiling height by 300–400mm.
Modern homes built with a trussed roof are trickier but not impossible — they may need the roof raised or the floor lowered, which we'll advise on honestly at the consultation. If the numbers don't work, we'll tell you before you spend anything.
Rule of Thumb Measure
Clear height is the minimum requirement measured from the top of the existing ceiling joist to the underside of the ridge board.
Planning, building regulations and party walls
Navigating local London council compliance and shared boundary frameworks.
Planning Permission
Many loft conversions — particularly rooflight and rear dormer designs — fall under permitted development. But if you're in an Mayfair conservation area, under an Article 4 Direction, adding a front-facing dormer, or your home is a listed building, full planning permission from Mayfair City Council (or the relevant district council) will usually be required. We assess this before any design work.
Building Regulations
Every loft conversion needs Building Regulations approval, regardless of whether planning permission is required. This covers structural strength, fire safety (mains-wired interlinked smoke alarms, fire doors and a protected escape route under Approved Document B), staircase design and insulation. We manage Building Control inspections in-house and hand you the completion certificate.
Party Wall etc. Act 1996
If you live in a terraced or semi-detached home and the work affects a shared wall — for example, bearing new steel beams onto it — you'll need to serve notice on your neighbours under the Party Wall Act. We guide you through this early so it never becomes a last-minute hold-up.
Loft conversions in Mayfair's period homes
Mayfair has a huge stock of Victorian and Edwardian terraces, and converting their lofts well takes experience. We match brickwork and roof tiles, detail dormers sympathetically to the streetscape, and work within conservation rules where they apply — so your conversion looks like it belongs, not bolted on.
Where head height or planning rules are tight, a mansard or L-shaped dormer often unlocks space that a standard dormer can't.
How we work
Consultation & feasibility
We measure head height, assess the roof structure and tell you honestly what's achievable.
Design
Architect-led drawings and the right conversion type for your home and budget.
Planning & approvals
Planning application, Building Regs and Party Wall process handled in-house.
Construction
Skilled trades, fixed price, weekly progress updates, your home kept clean and secure.
Handover
Full walkthrough, warranties, completion certificate and aftercare.
Why choose Crawford Construction
as your Mayfair loft builder.
FMB-listed Mayfair builder
A genuinely local, vetted FMB member — not a national chain covering Mayfair from out of county.
Everything in-house
Planning, structural work, Party Wall processes, and building control inspections handled under one roof.
Fixed-price, itemised quotes
Staged payments tied strictly to construction milestones completed.
One named project manager
James Crawford, Project Director, coordinates your entire build from start to snagging.
Period-property expertise
Specialized in matching Victorian brickwork, slate tiling, and navigating conservation rules.
10-year warranty
Full comprehensive insurance-backed structural guarantees for absolute safety.
Areas we serve
Loft conversions across Mayfair City Centre, Headington, Summertown, Jericho, Cowley, Iffley, North Mayfair and Botley, and throughout London — Witney, Bicester, Abingdon, Didcot, Kidlington, Woodstock, Thame, Banbury, Carterton and the Cotswolds.
Start your Mayfair loft conversion
Tell us about your project and we'll reply within 24 hours with the next steps. Free, no-obligation, and 100% confidential.
Frequently asked questions
Everything you need to know about loft conversions, staircase requirements, and planning permission.
For most Mayfair homes, yes — it's one of the cheapest ways to add a bedroom or office per square metre, and it can add notable value, often more than it costs, especially when it creates an extra bedroom. The honest exceptions are lofts without enough head height, where raising the roof can tip the cost-benefit the wrong way. We'll give you a straight answer at the consultation rather than after you've committed.
Often not. Many rooflight and rear-dormer conversions fall under permitted development. But conservation areas, Article 4 Directions, front dormers and listed buildings usually trigger a full planning application. Building Regulations approval, however, is always required — there are no exceptions.
Around 2.2m clear in the existing loft is the practical minimum, because the new floor structure, steel beams and insulation eat into it — you typically lose 300–400mm. Trussed roofs (common in homes built from the 1960s on) can still be converted but may need extra structural work. We measure this first, before anything else.
It uses some space on the floor below — that's unavoidable, and a pull-down loft ladder isn't permitted for a habitable room. The skill is positioning the staircase to lose as little usable space as possible, usually over the existing stairs. We design this in from the start so there are no nasty surprises.
If you're terraced or semi-detached and the work affects a shared wall, yes — you must serve notice under the Party Wall etc. Act 1996, and a neighbour can request their own surveyor. Starting this conversation early and amicably is the single best way to avoid delays, and we guide you through it.
Older homes often have a cold-water tank up there. It can usually be removed or relocated (frequently by switching to a combi or pressurised system), but it needs planning into the design and budget. We flag it at survey stage.
Most run around 6–10 weeks on site once approvals are in place, depending on type and whether a bathroom is included. You can generally stay in the home throughout; the work is mostly contained to the roof, and we keep access and mess to a minimum.
As a rough guide: Victorian terraces suit rear or L-shaped dormers; semi-detached and detached homes suit hip-to-gable, often with a dormer; mansards give the most space where planning allows; and rooflight conversions are cheapest where you already have head height. We recommend the option that gives the best value for your specific roof — not the most expensive one.
Let's build
somethingremarkable.
From first sketch to final handover — London's trusted team for homes built with precision, craftsmanship and care.
