Yes, you can do a loft conversion in a flat, but it takes more steps than in a house. You’ll usually need to buy the loft space from the freeholder, get their written consent, apply for full planning permission and meet stricter fire safety rules. Done properly, it can add a bedroom and significant value to a top-floor flat.
We see more and more Londoners in top-floor flats and maisonettes asking about loft conversions. This guide explains the legal and practical steps, so you know what to sort out before you spend money on drawings.
Who owns the loft above a flat?
This is the first thing to check, because in most cases it isn’t you.
Leasehold flats
Most leases leave the loft out of your flat. That means you may have no right to use it at all, not even for storage. To convert it, you’ll usually need to buy the loft space from the freeholder, who will normally expect a fair payment for it. They don’t have to sell, but most do.
The airspace above the roof
Owning the loft doesn’t always mean owning the airspace above and around the roof. That matters if you want a dormer or mansard, because both extend into that airspace. Check your lease, and if you buy the loft space, make sure the airspace is included where you need it.
Share of freehold
Owning a share of the freehold doesn’t give you the right to convert the loft on your own. You still need the agreement of the other freeholders, usually the owners of the flats below. Some estate agents suggest otherwise when selling flats with a share of freehold, so don’t rely on it.
Before you go further, ask a solicitor to check your lease and title. It’s a small cost compared with discovering a problem after the drawings are done.
What permissions do you need for a loft conversion in a flat?
| Approval | Needed? | What it involves |
|---|---|---|
| Freeholder’s consent | Yes | Written permission for structural work, usually as a licence for alterations |
| Planning permission | Yes | Flats have no Permitted Development rights for roof extensions, so a full application is needed |
| Building Regulations | Yes | Approval of the design and inspections during the build, with stricter fire rules for flats |
| Party wall notices | Usually | To the flat below and any attached neighbours |
Freeholder’s consent
Most leases allow small internal changes but ban structural work without the freeholder’s written consent. The freeholder doesn’t have to agree, and their main concern is protecting the building. Expect them to have your drawings and structural calculations checked by their own surveyor, at your cost.
Planning permission
Houses can often add a loft under Permitted Development, but flats and maisonettes can’t. Any change to the roof of a flat needs a full planning application. In England the householder planning fee doesn’t apply to flats, so check the current fee for your application with your council. Read our planning permission guide.
Building Regulations
Every loft conversion needs Building Regulations approval. For flats, fire safety rules are stricter, because the new floor affects how everyone in the building escapes (see below).
Party wall notices
The floor between your flat and the one below is a shared structure, and steel beams often sit on walls shared with the house next door. Both usually need party wall notices, served at least two months before the work starts. See our party wall guide.
Fire safety in a flat loft conversion
Adding a floor to a flat changes how people escape in a fire, so building control looks closely at it. Depending on the building, they may ask for:
- a protected escape route, with fire doors onto the stairs inside your flat
- fire-resisting floors and walls between your flat and the others
- mains-powered, linked smoke alarms on every level
- in some buildings, extra measures such as a sprinkler or misting system or an alternative escape route
The exact requirements depend on the height and layout of the building, so they need to be designed in from the start, not added later.
Water tanks and shared services in the loft
Lofts above flats often hold services the flats below rely on, such as cold water tanks or heating header tanks. Your neighbours need access to them for maintenance, so before conversion they usually have to be moved or replaced, for example by switching the flats below to mains-pressure water. Agree this with your neighbours and the freeholder early.
Roof maintenance and insurance
In many buildings, roof repairs are shared between all the leaseholders. After a loft conversion, the freeholder may ask you to take on full responsibility for the roof, recorded in a change to your lease.
Your share of the building insurance may also go up. Premiums are often split by floor area, so if your flat doubles in size, your share may rise. For example, a flat paying half the premium might move to two-thirds after the conversion.
Which types of loft conversion work in flats?
The same types as in houses, subject to planning:
- Rooflight (Velux): the simplest, because it doesn’t change the roof shape and doesn’t need extra airspace
- Rear dormer: adds headroom and floor space; needs the airspace above the roof
- Mansard: gives the most space and is common on London conversions and mansion blocks, where many councils support it
See our comparison of mansard and dormer loft conversions. If the building is in a conservation area, read our conservation areas guide too.
Own a top-floor flat? We can check your loft and lease situation and tell you what’s realistic before you commit.
How much does a loft conversion in a flat cost?
On top of the build itself, a flat loft has extra costs a house doesn’t:
- buying the loft space (and airspace) from the freeholder
- your solicitor, and the freeholder’s solicitor and surveyor, which you usually pay
- a full planning application
- moving water tanks and other shared services
- any extra fire safety measures
These vary a lot between buildings, so get advice on the legal side before you budget for the build. For build prices, see our loft conversion cost guide.
The reward can be significant. Turning a one-bedroom top-floor flat into a two-bedroom one, or a two-bedroom into three, often adds more value than the conversion costs. Ask a local estate agent for a before-and-after valuation.
Loft conversion in a flat: the steps in order
- Check your lease and title with a solicitor: who owns the loft, the airspace and the roof.
- Get a loft survey to see what’s physically possible and roughly what it would cost.
- Approach the freeholder (or the other freeholders) and agree a price for the loft space.
- Get plans drawn: planning drawings, Building Regulations drawings and structural calculations. Read our guide to loft conversion plans.
- Apply for planning permission.
- Get the freeholder’s licence for alterations, after their surveyor has checked the plans.
- Serve party wall notices and agree how shared services will be moved.
- Build, with building control inspections and a completion certificate at the end.
- Update your lease, insurance and roof responsibilities, and register the extra space.
Loft conversion in a flat: frequently asked questions
Can you do a loft conversion in a flat?
Yes, usually only in a top-floor flat. You’ll need the right to use the loft, the freeholder’s consent, full planning permission and Building Regulations approval.
Do I own the loft above my flat?
Often not. Most leases exclude the loft, so it belongs to the freeholder. Check your lease and title, and expect to buy the loft space if you want to convert it.
Do flats have Permitted Development rights for loft conversions?
No. Permitted Development for roof extensions only applies to houses, so a loft conversion in a flat always needs a full planning application.
Can the freeholder refuse a loft conversion?
Yes. Unless your lease says otherwise, the freeholder doesn’t have to sell you the loft or agree to the work. Most will agree for a fair price and with proper drawings.
I own a share of the freehold. Do I still need permission?
Yes. You need the agreement of the other freeholders, usually the owners of the flats below.
Will a loft conversion add value to my flat?
Usually, especially if it adds a bedroom. The gain depends on your area and on the cost of buying the loft space, so get a local valuation before you start.
Thinking about a loft conversion in your flat?
A loft conversion in a flat takes longer to set up than in a house, but with the right guidance it’s very achievable. We’ve helped flat owners across London work through the freeholder, planning and fire safety stages, and we can tell you early on whether your loft is worth pursuing.
