Converting a loft in a flat or maisonette

Loft conversion planning permission for a flat is required in every case, because the permitted development rights that let a house owner build a dormer without an application do not exist for flats. Part 1 of the General Permitted Development Order applies to dwellinghouses, and the Order's own definition excludes a building containing one or more flats, and a flat contained within such a building. Maisonettes are caught by the same exclusion.

So the comparison people make with the neighbouring terraced house is not a useful one. The house next door can convert its loft under Class B. The maisonette cannot, whatever the roof looks like from the street.

Why Part 1 does not apply to flats

The exclusion is definitional rather than discretionary. It is not an Article 4 direction, it is not a local policy, and no council can waive it. A top-floor flat with sole use of the roof space and its own front door is still a flat for these purposes.

That has a knock-on effect people discover late. The rest of Part 1 goes with it: no permitted development for rooflights, no dormer allowance, no rear extension right, no outbuilding right in the shared garden, no chimney or flue right. Every external alteration to a flat is either not development at all, because it is internal, or it needs planning permission.

Internal works remain outside planning control. Opening up a loft hatch, insulating and boarding the void for storage, or fitting a fixed staircase within the flat are internal alterations, provided nothing changes outside and no separate unit is created. The moment a rooflight, a dormer or a raised ridge appears, an application is needed.

The application, the drawings and the fee

The application is a full planning application rather than the householder route, because the householder application type and its lower fee apply to houses. Take the current figure from the published fee schedule, since the fees are indexed annually and the categories are easy to misread.

The drawings have to show the whole building rather than your flat alone. Existing and proposed elevations of the full elevation to which the dormer relates, a roof plan, sections through the building showing floor to ceiling heights, and a site plan identifying the flat within the block. Officers assess the effect on the building as a whole and on the street, and a drawing set that stops at your ceiling makes that impossible.

Where the block sits in a conservation area or the building is listed, a heritage statement assessing the effect on the character of the area or the special interest of the building is normally a validation item. A roofscape of unbroken slate with regular chimney stacks is exactly the kind of feature a conservation area appraisal identifies as characteristic.

A short planning statement dealing with policy, amenity and design is worth including even where it is not on the local list, because the officer's report will have to address those points anyway.

Roof space ownership, leases and freeholder consent

This is where most maisonette loft schemes fail, and it has nothing to do with planning.

Long leases usually demise the flat itself and stop at the ceiling. The roof structure, the void above it and the airspace are typically retained by the freeholder, which means the leaseholder has no right to build there even with planning permission. Acquiring that right takes a deed of variation to extend the demise, or a separate grant of the airspace, and the freeholder can charge for it or refuse.

Read the lease before you commission drawings. The clauses that matter are the extent of the demise, any covenant against alterations, any requirement for landlord's consent not to be unreasonably withheld, and the service charge and repairing obligations for the roof.

Planning permission does not override any of this. A permission granted to a leaseholder who has no interest in the roof space is a permission that cannot be implemented, and the application will have required an ownership certificate acknowledging that another owner exists, with notice served on the freeholder. Serving that notice is how many freeholders first hear about the scheme, so speak to them first.

Fire escape from a new top storey

Adding a storey to a flat changes the escape strategy for the flat and can affect the block. Approved Document B treats each new storey as adding to the travel distance and to the escape problem, and a new top-floor room in a maisonette generally needs a protected route to the flat entrance door, self-closing fire doors, interlinked detection, and in some layouts a sprinkler or misting system.

Two further points apply in a block rather than a house. The common parts and the compartmentation between flats are the freeholder's responsibility and your works must not compromise them. And where the building is tall enough to fall within the higher-risk regime under the Building Safety Act 2022, an entirely separate approval process applies, and any relevant development also needs a fire statement at the planning stage. Most two-storey maisonettes fall well outside that, but check the building height before assuming so.

Engage building control early. A design that works on paper for planning can be undeliverable once the escape route is drawn.

Neighbour amenity in a converted terrace

The planning assessment focuses on three things: the effect on the appearance of the building and the street, overlooking, and loss of light.

Dormers on a front roof slope in a terrace are usually resisted where the roofscape is uniform. Rear dormers are more often acceptable, subject to being set below the ridge, above the eaves and in from the party walls, which are the same design conventions councils apply to houses even though the permitted development limits do not apply.

Overlooking is the sharper issue in a flat conversion, because a new rear window at second-floor level can look directly into the neighbouring garden and rear rooms at closer range than any ground-floor extension. Obscure glazing to flank windows, and roof lights set high enough that the sill is above eye level, are the usual answers. Loss of light to the flat below or next door is assessed in the same way as for any extension, and the 45 degree rule as officers apply it is a reasonable first test of whether a rear dormer will cause a problem.

Structural work into a party wall, including steels bearing on a shared wall, brings the Party Wall etc. Act 1996 into play with its own notice periods.

What to submit

Assemble the pack in this order and the application is usually straightforward:

1. Existing and proposed plans, elevations of the full building, sections and a roof plan.
2. Site location plan and block plan identifying the flat.
3. The correct ownership certificate, with notice served on the freeholder and any other owner.
4. Heritage statement where the building is listed or in a conservation area.
5. Planning statement covering design, amenity and policy.
6. Evidence that the lease position is resolved, or at least a note explaining it.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

Enter your postcode on PlanScope to see which supporting documents a flat conversion application needs. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.