Architect-led conversion of unused roof space into a proper room — a primary bedroom and en-suite, a home office or a playroom. Dormer, mansard, hip-to-gable and rooflight conversions, designed, engineered and built by RIBA Chartered architects, in-house structural engineers and directly-employed trades under one fixed-price contract, from first survey to handover.
An attic conversion is the most cost-effective way to add a bedroom and bathroom to a London house, because the structure that matters — the walls and foundations — is already there. You are not building outward into a garden or down into the ground; you are claiming volume you already own and pay for, and turning it into the room your family actually needs.
Attic conversion and loft conversion are the same thing — the words are used interchangeably across the UK. Whichever term you searched, this is the page for converting the space under your roof into a habitable room, designed and built under one fixed-price contract by a single team of architects, structural engineers and our own trades. If you already know the specific style you want, we also detail dormer, mansard, hip-to-gable and rooflight conversions on their own pages.
The difference between a good attic conversion and a poor one is almost never the finish — it is the things you cannot see once it is done: whether the floor was properly strengthened, whether the staircase lands with real head height, whether the insulation actually keeps the room warm in winter and cool in summer, and whether the fire-escape strategy genuinely complies. Get those right and the room works for thirty years. Get them wrong and you have an expensive box that is too hot, too cold, or quietly non-compliant.
We have converted roof space across NW3, NW8, NW1, NW11, N6, W1 and SW London — Victorian terraces in Primrose Hill, Edwardian semis in Hampstead Garden Suburb, and mansion-block top floors in St John's Wood. Every roof is different. Every conversion is held to the same standard: surveyed properly, engineered honestly, and finished to match the house below.
The right type depends on your roof shape, the head height you have, your budget and the local planning context. These are the six approaches we use most across London.
The existing roof line is kept and conversion windows are set into the slope. Ideal where you already have generous head height and want minimal disruption, lowest cost and the easiest planning route — almost always Permitted Development.
A flat-roofed box built out of the rear slope to add full head height and usable floor area across most of the footprint. The workhorse of London attic conversions — the best balance of space gained, cost and planning ease on terraces and semis.
The sloping “hipped” side of the roof is rebuilt vertically to a gable end, creating significant extra volume — usually combined with a rear dormer for a full primary suite. The standard move for 1930s semis and Edwardian end-terraces with a hipped roof.
The roof is rebuilt to a near-vertical profile with a shallow top, maximising floor area and head height across the whole plan. Often the only style acceptable to conservation officers in areas such as Hampstead and Belgravia, and the most generous space you can win from a roof.
Two dormers — one over the main roof and one over the original rear closet/return — joined in an L to deliver two or even three rooms plus a bathroom. The high-value option on period terraces with a rear addition, and our most-requested conversion in NW London.
Where the existing head height is below the usable threshold, we either raise the ridge (subject to planning) or lower the ceilings of the rooms below to borrow height. A specialist route that rescues conversions which would otherwise be impossible — assessed carefully at survey.
Every line item below is delivered, certified and warranted under the same fixed-price agreement — not bolted on as an extra once the scaffold is up.
New floor joists or steel beams to carry the new room's load to the supporting walls, calculated by our MIStructE engineers. Roof structure altered, propped and rebuilt for dormers, hip-to-gable or mansard, with padstones and steel to specification.
A new compliant staircase designed at concept stage, with the correct pitch, going and head height under Building Regulations Part K, detailed to sit elegantly over the existing stair and to take as little space as possible from the floor below.
New circuits from the consumer unit, architectural LED lighting, ample sockets with USB, data cabling, and radiators or underfloor heating extended from the house system — sized so the new room is genuinely comfortable, not an afterthought on an overloaded circuit.
Warm-roof insulation to current Building Regulations Part L — rigid PIR between and over rafters — with controlled ventilation to prevent condensation. The single biggest factor in whether your attic room is usable in July and January.
Dormer construction with insulated walls and roof, lead or GRP detailing and matching tile or slate cheeks; or Velux/conservation rooflights set flush into the slope. Glazing positioned for light, view and (where overlooked) privacy.
A fully tanked en-suite or shower room with concealed cistern sanitaryware, brassware to specification, underfloor heating and a properly routed soil and water supply — planned into the structural design so it lands exactly where you want it.
The protected escape route, fire doors to habitable rooms, mains-linked interlinked smoke alarms and, where the layout requires it, a sprinkler or escape window — designed to satisfy Building Control, which is mandatory on every attic conversion.
Bespoke joinery that turns the low eaves — otherwise dead space — into fitted wardrobes, drawers and storage. Internal doors, skirting and architrave matched to the period of the house, made in our own joinery shop.
Plasterboarding and skim to all surfaces, a full multi-coat decoration system, and specialist finishes on request — bringing the new room up to exactly the standard of the rooms below, so it reads as part of the house, not a conversion.
Engineered timber, carpet or natural stone in the bathroom, laid on an acoustically isolated, level deck — with resilient layers between the new floor and the rooms below to keep footfall noise down.
We prepare and submit any planning application or Lawful Development Certificate, the full Building Regulations submission, and serve Party Wall notices where the work affects a neighbour — all coordinated in-house through our sister surveying company.
A two-stage snag — our team first, then a joint walk with you — defects fixed before completion. A 12-month defects period, a 10-year workmanship warranty and a free service visit at six months.
Most London roofs can be converted, but a handful of factors decide which type is possible and what it costs. We check all six at the survey, before any money is committed.
The decisive factor. You generally want at least 2.2–2.4m from the existing ceiling joists to the ridge over a usable area. Below that, a dormer, a roof lift or a lowered ceiling can recover the height — or a rooflight conversion may not be viable at all.
Traditional “cut” roofs with rafters and purlins convert easily. Modern trussed roofs (common post-1965) fill the space with timber webs and need engineered alterations — still very doable, but it affects cost and method.
A steeper pitch gives more usable floor area within the slope; a shallow pitch usually points towards a dormer or mansard to win head height. The pitch also shapes which conversion type looks right on the house.
There has to be somewhere to land a compliant stair with head height at the top. This is the most common reason a layout needs rethinking, so we resolve it first — usually rising over the existing stair.
Old cold-water and expansion tanks in the loft are removed and the system converted to mains-pressure, freeing the space. Existing flues, soil stacks and any solar equipment are surveyed and re-planned.
Whether you are in a Conservation Area, have a Listed building, or sit under an Article 4 direction determines which conversion types are acceptable and whether Permitted Development applies — we check the constraints for your exact address.
We work to the RIBA Plan of Work 2020. Here is what each stage means for your attic conversion, and what you receive at the end of it.
An initial consultation at our studio or your home. We discuss what you want the room to be, look at the roof, and talk realistic budgets and conversion types. No charge, no obligation.
A measured survey of the roof, head-height assessment, roof-structure inspection and a written feasibility report setting out which conversion type suits your house, the planning route and an outline cost band.
The room layout, the all-important staircase position and the dormer or roof form developed and presented — with a 3D walk-through so you can see exactly how it affects the floor below before committing.
We prepare and submit a planning application or a Lawful Development Certificate as appropriate, manage any consultee correspondence, and run the Building Regulations submission in parallel.
Full structural calculations, the detailed drawing pack the trades build from, fire-strategy details, and a written specification — everything fixed before a tile is lifted.
Scaffold, roof opening, structural floor and steel, dormer or mansard build, weathertight envelope, then first fix, insulation, plaster, second fix, en-suite and decoration. Weekly progress updates throughout.
Deep clean, commissioning, a joint snagging walk, the certification pack (electrical, structural, building control completion) and key handover.
A 12-month defects rectification period, a six-month service visit and a 10-year workmanship warranty.
What an attic conversion costs depends on the specification you choose. Here is exactly how our four tiers differ.
For a representative high-end rear-dormer attic conversion at around £75,000, here is the honest breakdown of where every pound is spent.
An attic conversion is a structural and fire-safety exercise before it is a decorating one. Here is what is being calculated and installed.
Whether your attic conversion needs planning permission is one of the first things we resolve — it shapes the type, the timeline and the cost.
Many attic conversions can be built under Permitted Development rights, which avoids a full planning application. Rear and side dormers are generally allowed within volume limits — 40 cubic metres for terraced houses and 50 cubic metres for detached and semi-detached homes — provided they sit below the ridge, are set back from the eaves and use materials similar to the existing house. A Lawful Development Certificate is still worth obtaining to confirm the work is lawful, particularly for resale.
Planning permission is usually required for a front-facing dormer, for any change to a Listed building, for homes in a Conservation Area where Permitted Development is restricted, and where an Article 4 direction has removed those rights — common in the conservation areas of Hampstead, Belgravia and Kensington. A mansard is frequently the only roof form a conservation officer will accept in these areas, and we have a strong track record securing consent for them.
We assess your exact address at the feasibility stage, advise on the most likely route, and then prepare and manage whichever application is needed — planning, Lawful Development Certificate, or Listed Building Consent — alongside the Building Regulations submission and any Party Wall notices. For an early budget while you weigh it up, use the cost calculator.
A representative programme for a rear-dormer attic conversion with an en-suite. Yours will differ by type, but this is what a properly run conversion looks like in real time.
Plenty of firms will convert a loft. Here is what makes ours worth the difference.
One agreement covering design, approvals, structure, fire safety and finishes. No cost-plus surprises once the scaffold is up.
The same studio designs the layout, calculates the structure and details the fire strategy — nothing falls between separate consultants.
We resolve the hardest part — landing a compliant stair with head height — at concept stage, before you commit.
Our core carpenters, roofers and plumbers are PAYE staff, not gig labour — continuity of standard from job to job.
Successful dormer and mansard consents across Camden, Westminster and RBKC, where many firms struggle.
Professional indemnity and public liability at £10M, well above industry standard.
An insurance-backed workmanship warranty protecting your conversion long after completion.
We programme to get your roof open and re-closed quickly, minimising the period your home is exposed.
An attic conversion often sits within a wider project. Start here to understand the related options, or speak to us about combining them under one contract.
Our full loft conversion hub — the same service under its other common name, with every conversion type detailed.
The most popular type — a dormer adds full head height and floor area across the rear roof.
Maximum space and the usual choice in Conservation Areas — a full roof rebuild to a near-vertical profile.
For semis and end-terraces with a hipped roof — rebuilding the side vertically to win volume.
The en-suite that turns an attic room into a true primary suite — fully tanked and warranted.
Combining a loft with a rear or side-return extension — the classic whole-house space gain.
Folding an attic conversion into a wider whole-house renovation, delivered as one programme.
A deeper look at what drives the price — useful before you set a budget.
Comparable projects with real roofs, real planning constraints and real finishing standards. Start with our Hampstead loft conversion case study, then browse the wider case-study hub. For survey-led due diligence before you commit, see surveying support.
Period-house loft conversions adding bedrooms and en-suites within conservation constraints.
View case study →Five-storey period house with loft works as part of a whole-house programme.
View case study →Loft conversion combined with a double-storey rear/side extension and full renovation.
View case study →Browse the full portfolio of conversions, extensions and renovations across prime London.
View portfolio →“I would like to thank Ross and his team for their consistent commitment to quality and their unerring reliability. They delivered our property to specification and on time, proving to be an extremely effective, experienced, and proactive contractor.”
“We have worked with Ross and his company many times. They are extremely professional and hardworking individuals who can work under any circumstances. There was no variation to the works.”
Book a no-obligation consultation at our Finchley Road design studio or in your home. The first meeting is free, lasts 60–90 minutes, and concludes with an honest indication of feasibility, programme and budget band. No salespeople. No pressure.
Site visit · feasibility assessment · outline cost estimate · programme indication. No obligation. Saturday appointments available.