One of the most common planning misconceptions among flat owners is that they have the same permitted development rights as house owners. They don’t. If you own a flat or maisonette in the UK, the permitted development rights that allow house owners to extend, convert lofts, and alter roofs without planning permission simply do not apply to you. This guide explains why, and what your options are.

Why Flats Don’t Have Permitted Development Rights for Extensions

Permitted development rights under Schedule 2, Part 1 of the Town and Country Planning (General Permitted Development) (England) Order 2015 apply only to dwellinghouses. The legal definition of a dwellinghouse does not include a flat or maisonette.

This means that the following permitted development rights — which house owners routinely use — are NOT available to flat owners:

• Class A: Single-storey and two-storey extensions
• Class B: Roof alterations (adding dormers)
• Class C: Other roof alterations (rooflights)
• Class D: Porches
• Class E: Outbuildings and garden structures
• Class G: Chimney stacks and flues

Any physical alterations to the external appearance of a flat that would require these rights instead require full planning permission from the local authority.

What Flat Owners Can Still Do Without Planning Permission

While external works require planning permission, many internal works do not:

• Internal layout changes: Removing or adding non-load-bearing internal walls
• Kitchen and bathroom refits: Replacement using the existing positions (though drainage changes may need building regulations)
• Flooring: Replacing or upgrading flooring (though acoustic performance requirements apply in certain cases)
• Decorating: All internal decoration
• Like-for-like window replacement: Replacing existing windows in the same aperture, same style — though some leases require freeholder consent for this

Note: Even if planning permission is not required, your lease agreement will almost certainly have restrictions on what you can do without freeholder consent. Always check your lease before making any alterations.

The Leasehold Dimension: A Separate Layer of Consent

Most UK flats are sold on leasehold — meaning you own the flat but not the building (the freehold). Your lease will typically require you to obtain the freeholder’s consent for:

• Structural alterations of any kind
• Alterations visible from outside the building
• Changes to the drainage, plumbing, or electrical system
• Subletting (in many leases)
• Running a business from the flat

Freeholder consent is separate from and additional to planning permission. You need both if both apply. Freeholders can impose conditions and typically charge “licence fees” for consent to alterations.

Applying for Planning Permission as a Flat Owner

If you want to make external alterations to your flat — add a roof terrace, install a dormer (if you own the top-floor flat), or extend in some other way — you must apply for planning permission. The process is the same as for any householder application:

• Instruct an architect to produce the required drawings
• Submit via the Planning Portal or your LPA’s portal
• Pay the application fee (£258 for a householder application in England, 2025)
• Wait for the LPA to determine the application (typically 8 weeks)

The planning assessment will consider the same factors as for any residential application: design, impact on neighbours, character of the area. For a top-floor flat seeking a roof terrace or dormer extension, the LPA will also consider the visual impact on the streetscape and neighbouring properties.

Common Scenarios: What Flat Owners Often Want to Do

Top-Floor Flat: Adding a Loft Conversion or Dormer

If you own the top-floor flat and have the roof space in your ownership (check your lease — the roof structure and air space is sometimes excluded from the top-floor flat’s leasehold), you may be able to apply for planning permission for a dormer or loft conversion. This requires:

• Ownership of the air space / roof included in your lease (or the freehold)
• Full planning permission (not permitted development)
• Freeholder consent (if not the freeholder yourself)
• Building regulations approval
• Potentially a deed of variation to your lease to include the new space

Ground-Floor Flat: Adding a Garden Outbuilding

If you have exclusive use of a garden as part of your lease, outbuildings in that garden may require planning permission (as the Class E permitted development right doesn’t apply to flats). Small sheds or garden buildings may still require planning permission depending on size and local rules.

External Cladding or New Windows

Changing the external appearance of a flat building — cladding, new window styles, new front door — requires planning permission. Many flat owners assume window replacement is routine, but for flats, it may require planning permission (and certainly requires freeholder consent).

Frequently Asked Questions

Can a flat owner extend under permitted development?

No — permitted development rights for extensions, roof alterations, and outbuildings apply only to dwellinghouses, not flats. Any external works to a flat require planning permission.

Can I add a terrace to my top-floor flat?

Potentially — but you need planning permission, freeholder consent (if leasehold), and building regulations approval. Planning authorities will assess the impact on overlooking, privacy, and the character of the roof. Crown Architecture can advise on the prospects for your specific situation.

Do maisonettes have permitted development rights?

No — maisonettes, like flats, do not benefit from the dwellinghouse permitted development rights in Part 1. All external works require planning permission.

What planning rights do houses converted to flats have?

If a Victorian house has been converted to flats, the permitted development rights for extensions and roof alterations are removed — because the building is now a flat conversion, not a dwellinghouse. The building’s planning use class determines what rights apply, not its original form.

Can Crown Architecture help me with a planning application for my flat?

Yes — Crown Architecture handles planning applications for flats, including top-floor extensions, roof terraces, and alterations requiring consent. Call us on 07443 804841 to discuss your project.