We are loft conversion specialists handling dormer, hip-to-gable, Velux and mansard conversions across South London and North Kent. That covers the whole job — structural steel, the new floor, the roof alteration, the staircase, insulation, fire compliance and the second fix joinery. Converting a loft is one of the few ways to add a full bedroom without losing any garden, and on most houses it is the cheapest square metre you will ever add.
A loft conversion is a structural job that happens to end in a bedroom. The existing ceiling joists were never designed to carry a room, so the floor has to be rebuilt on steel. The roof usually needs opening up or partly rebuilding. And the new staircase has to land somewhere that works on the floor below without wrecking the layout you already have.
We survey the roof structure and the head height first, because those two measurements decide which conversion types are even possible on your house. From there we handle the structural calculations, the building regulations package, and a planning application where the conversion falls outside permitted development.
On site that means steel beams and a new floor structure, the roof alteration itself, insulation to current standards, fire-rated doors and a protected escape route, the staircase, and full first and second fix. Our own carpenters build the staircase and handle the joinery, which is usually where the finish quality of loft extensions is won or lost. It is one continuous programme rather than a series of separate loft conversion services booked one after another.
Your roof shape, its structure and the head height available decide which of these is possible. We will tell you which ones work on your house before any design fees are spent.
The most common conversion in London terraced and semi-detached housing. A flat-roofed box extends out from the rear roof slope, adding both floor area and full standing height across most of the new room. A dormer loft conversion usually falls within permitted development, which makes it quicker to get started than the alternatives.
Suits end-of-terrace, semi-detached and detached houses with a hipped roof — one that slopes on three or four sides. The sloping side is rebuilt vertically to form a gable wall, squaring off the loft and adding a significant amount of usable width. It is frequently combined with a rear dormer to get the most out of the space, and the hip to gable loft conversion cost reflects that it involves rebuilding part of the roof rather than just cutting into it.
The least invasive option. The roof structure stays exactly as it is and rooflights are fitted into the existing slope. Considerably faster and cheaper — the velux loft conversion cost is the lowest of any type — but it only works where the existing head height is already sufficient, typically 2.4 metres or more at the ridge.
The most extensive conversion. The rear roof is rebuilt to an almost vertical slope, creating close to a full additional storey. A mansard loft conversion produces more space than any other option but nearly always needs full planning permission, and it is common on period properties in conservation areas where other roof alterations are restricted.
Extends the dormer over the rear outrigger as well as the main roof, forming an L. An l shaped dormer loft conversion is typical on Victorian terraces with a back addition, and it can produce two rooms rather than one — often a bedroom and an en-suite, or a bedroom and a study.
Where the new stairs land is often the hardest part of the design and the thing most often glossed over at quoting stage. We work it through at survey, because a conversion that costs you a bedroom on the floor below to gain one in the loft is rarely worth doing. Our carpentry team builds the staircase to building regulations standard as part of the job.
Eight stages, in this order. The first two matter most — they decide whether the project is worth doing at all.
Head height is the constraint that decides everything about a loft conversion, and it is the measurement most often skipped over at quoting stage. We measure it before discussing design, and we will tell you plainly if a conversion is not viable rather than starting a job that ends in compromise.
Fire compliance is the other place loft conversions commonly fall short. Adding a storey changes the escape route for the entire house, which means fire doors, interlinked alarms and often work on the floors below. It is in our quotation from the outset rather than appearing as a variation once building control raises it.
We are also a loft and extension company rather than loft builders alone, so if you are weighing a conversion against a rear extension — or considering doing both — you get an honest comparison from someone who builds either.
Balham, Clapham, Brixton, Streatham, Tooting, Wimbledon, Mitcham, Worcester Park
Gravesend, Northfleet, Dartford, Meopham, Higham, Shorne, Cobham, Ebbsfleet
Based in Balham SW12 and working across South London and North Kent.
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Call 07472 137237 and ask.
Floor area matters less here than it does on an extension. Two lofts of identical size can price very differently depending on these:
We quote in writing after a site visit, itemised by stage, so you can compare it properly against anyone else’s.
Tell us what you are planning and we will arrange a site visit. We will measure the head height, tell you which conversion types your roof allows, and give you a written quotation you can compare.
Detailed insights into our operational standards, project management philosophy, and technical capabilities.
Often not. Many rear dormer and rooflight conversions fall under permitted development, subject to volume limits — broadly 40 cubic metres of added roof space for a terraced house and 50 cubic metres for a detached or semi-detached house. The extension must not sit higher than the existing ridge, must not extend beyond the roof slope on the elevation facing a highway, and generally has to be set back from the original eaves. Mansard conversions, front-facing dormers, flats and maisonettes, and properties in conservation areas usually need full planning permission. We confirm which applies at survey stage.
As a working rule you want at least 2.2 metres measured from the top of the existing ceiling joists to the underside of the ridge. Below roughly 2.0 metres you are looking at either lowering the ceilings in the rooms beneath or raising the roof, both of which change the cost significantly. Building regulations also set a minimum headroom over the new staircase, which is why the stair position and the head height have to be assessed together rather than separately. We measure this before discussing anything else.
A rooflight conversion typically takes six to eight weeks on site. A rear dormer usually runs eight to twelve weeks, and a hip-to-gable or mansard twelve to sixteen. Design, approvals and structural calculations happen before any of that and generally add eight to twelve weeks. You are usually able to stay in the house throughout, since most of the work happens above your ceiling until the staircase goes in.
Usually yes, but it involves more structural work. Modern trussed roofs use W-shaped timber webs that fill the loft space, so they cannot simply be cut away. They are removed and replaced with a new structural arrangement, typically steel beams supporting new floor joists and rafters. It is entirely achievable and we do it regularly, but it costs more than converting a traditional cut roof, and it is one of the first things we check at survey.
For a loft to count as habitable space it needs a fixed staircase that meets building regulations. A loft ladder is only acceptable where the space is used for storage. Without a compliant staircase the room cannot legally be described as a bedroom, which also affects valuation and comes up during conveyancing when you sell.
Only if it has building regulations sign-off. A converted loft without a completion certificate cannot be marketed as a bedroom, and its absence is routinely picked up by solicitors during a sale, which holds things up at exactly the wrong moment. This is why we take every conversion through building control to formal sign-off and hand you the certificate at the end.
In most cases yes. Adding a second or third storey changes the escape route for the whole house, so building regulations typically require fire-rated doors to habitable rooms off the stairwell, interlinked mains-powered smoke alarms, and a protected route from the top floor to the final exit. It sometimes means replacing doors on the floors below as well. We include all of this in the quotation from the start rather than raising it later as an extra.
Usually, and it is one of the most common requests. The main considerations are where the waste can run to connect with the existing soil stack, and whether the position needs a pump. Head height matters too — a shower needs standing height, so it often sits under the highest part of the roof or inside the dormer. We work this out at design stage rather than assuming it will fit.
