Loft conversions that add the room your home is missing
Velux, dormer, hip to gable and mansard conversions, from the structural work and staircase to a finished, decorated room.
The easiest room to add is often the one already above your head, sitting empty. Left as it is, it is storage. Done properly, it is a master suite, a home office or the extra bedroom that means you do not have to move. A loft conversion is usually the most cost effective way to add real, usable space without losing any of your garden.
We handle the whole job, from the structural steels and the new staircase through to the plastering, the en-suite and the final coat of paint. You get one team for all of it, not a loft company that walks off once the shell is up.
Firtree Build is a North London loft conversion company creating extra bedrooms, offices and bathrooms from unused loft space. We build dormer, mansard and hip to gable conversions across North London, Enfield and Hertfordshire, managing the whole project from design and planning to a finished, decorated room.
Types of Loft Conversions
Dormer loft conversion
The most popular choice across North London. A box dormer built out from the rear roof slope gives full standing headroom and a proper floor, usually enough for a double bedroom with an en suite. Suits most Victorian and Edwardian terraces and 1930s semis, and many can be built under permitted development.
Mansard loft conversion
The largest type of loft conversion. The roof slope is rebuilt almost vertically with windows set into it, effectively adding a new storey. Common on London terraces, with room for two bedrooms or a bedroom and bathroom. It usually needs full planning permission, which we manage, and takes longer on site than a dormer.
Hip to gable loft conversion
For semi detached and end of terrace homes with a sloping side roof. We build the sloping side up into a vertical gable wall, opening up the loft and making room for a proper staircase. Often combined with a rear dormer to get the most space from a 1930s semi.
Velux or Roof light conversion
The simplest and least disruptive option, for lofts that already have enough height. Roof windows are fitted into the existing slope with no change to the roof shape, so it is usually quicker and lower cost. Ideal for a home office, guest room or playroom.
Roofs, party walls and planning
North London’s Victorian and Edwardian roofs each behave differently, and party walls and access need handling with care. Many conversions fall under permitted development, but conservation areas across Enfield and North London have their own rules. We tell you at the quoting stage exactly what your roof allows, which route your project needs, and what it will cost, so there are no surprises once the scaffolding is up.
Why Firtree for your Loft
You get a detailed, line by line quote before anything starts, and an honest conversation about where the budget could move, so you commit to a number you understand. And because you live with a loft every day, we do not use the cheapest trades to shave a quote. The joinery, the tiling and the details behind the plaster are held to the same standard as the parts you can see.
how it works
Consultation, quote, then a well managed build.
01
Consultation
We visit, listen, and advise on the best option for your home and budget.
02
Quote & design
An itemised quote and a design, with planning handled where needed.
03
Managed build
A well managed build, start to finish, with regular updates.
“A lighter, larger home that works for your family and adds real value, finished by a team you could actually trust.”
What we build
Work that speaks for itself
FREQUENTLY ASKED QUESTIONS
Good to know before you get in touch
How long does a loft conversion take in North London?
A rooflight (Velux) conversion typically takes 4 to 6 weeks on site, a rear dormer 6 to 10 weeks, a hip to gable 8 to 12 weeks, and a mansard 10 to 14 weeks. Add around 6 to 10 weeks beforehand for drawings, structural calculations and building control. Most standard dormer conversions in Enfield and North London run about 4 to 5 months from first drawing to finished room, or 7 to 9 months if planning permission and a party wall agreement are involved. Firtree confirms your programme once the design is set.
How much does a loft conversion cost in North London?
As a 2026 London guide, a rooflight conversion is typically £60,000 to £78,000 all in, a rear dormer £72,000 to £98,000, a hip-to-gable £80,000 to £115,000, and a mansard £95,000 to £145,000, including VAT. The dormer is the most common choice across North London terraces and semis because it adds the most usable head height for the money. Firtree prices to a fixed quote on your agreed drawings.
How much value does a loft conversion add?
A loft conversion typically adds 10 to 15% to the value of a North London home, and a well designed dormer or mansard that creates a proper double bedroom with an en suite can push that towards 20 to 25%. On a £600,000 Enfield property that is roughly £60,000 to £150,000. An extra bedroom is one of the highest return improvements you can make in North London, where buyers pay a clear premium for a fourth or fifth bedroom.
Do I need planning permission for a loft conversion?
Most loft conversions on houses fall under permitted development and do not need planning permission, as long as you stay within the volume allowance (40 cubic metres for a terraced house, 50 cubic metres for a semi detached or detached house) and do not extend beyond the front roof slope. Permitted development does not apply to flats or maisonettes, and conservation areas or Article 4 directions can remove it, so a mansard or front facing work usually needs full planning. Building Regulations approval is always required.
Is my loft high enough to convert?
As a rule of thumb you need at least 2.2 to 2.4 metres from the top of the existing ceiling joist to the ridge, because the new floor, insulation and ceiling finishes take up around 200 to 300mm. Measure at the tallest point of the roof. If you are short on height, a dormer or mansard can create the space by reshaping the roofline, and the older Victorian and Edwardian roofs common across North London often have more room than owners expect. Firtree checks this on a free visit.
Where will the new staircase go?
The new staircase normally rises from the existing landing, so it connects cleanly to the floor below and meets building regulations. Its position shapes both the loft layout and the room beneath it, so it is worth deciding early. In typical North London terraces, the new staircase usually runs directly over the existing staircase to save floor space. Firtree plans this at the design stage, so you do not lose a bedroom to it.
Can we stay in the house during a loft conversion?
Usually, yes. Most of the structural work happens up in the loft and is reached through external scaffolding, so the rest of the house stays liveable for much of the build. The disruptive phase is when the staircase opening is cut through to connect the loft to the landing, which lasts a few days. Firtree schedules that with you in advance.
Ready when you are
Ready to talk about
your extension?
Tell us what you have in mind and we will come back with honest advice and a clear quote.