Planning · Flats
Extending a flat or maisonette
Flats have no permitted development rights at all — and the freeholder's consent is a separate hurdle from the council's.
No permitted development, at all
Permitted development rights apply to houses. They do not apply to flats or maisonettes. Any external alteration — a rear extension, a roof extension, a new window opening — requires a full planning application.
This surprises people who have watched a neighbour in a house extend without applying for anything. The difference is the property type, not the street.
The lease is the other half of the problem
Planning permission gives you the council's consent. It does not give you your freeholder's. Almost every lease requires the landlord's written consent for structural alterations, and many require it for far less — changing floor coverings, moving a bathroom, altering plumbing.
Obtaining a licence to alter takes time and normally involves paying the freeholder's legal and surveyor's costs. Start it early, in parallel with the planning application rather than after it, or it becomes the thing holding up the programme.
What is usually achievable inside
Internal refurbishment of a flat is generally straightforward from a planning point of view, though it may still be notifiable under the Building Regulations — new electrics under Part P, altered drainage, and any structural opening.
Removing an internal wall in a flat needs the same structural rigour as in a house, plus lease consent, plus consideration of sound insulation between dwellings under Part E where the works affect separating floors or walls.
Ground-floor flats with gardens
A ground-floor flat with a demised garden is the one case where a rear extension is often realistic. It still needs full planning permission and freeholder consent, and it needs the upstairs leaseholder's position to be considered, but it is a common and consentable project in London.
The structural question is whether the extension can be built without relying on the structure above, and that is an engineer's judgement made at survey stage.
This guide describes national rules for England and was written to be accurate at the time of publication. Local designations can restrict them further, and legislation changes. Always confirm the position for your own address with your local planning authority, or ask us to do it in writing.
Answers
Questions we get asked alongside this
Do I need planning permission for building work in London?
It depends on the property type and what is proposed. Many single-storey rear extensions and loft conversions fall under permitted development, but those rights do not apply to flats and are restricted in conservation areas or where an Article 4 direction applies. We check the planning position for your specific address before quoting, and tell you in writing which route applies.
How do you price the work?
From a site survey, written up as a fixed and itemised scope before any deposit is discussed. If something genuinely unforeseen appears once work is opened up, it is priced and agreed in writing before we continue — never added to the final invoice after the fact.
When do I pay?
In arrears of work completed. You pay for work that has been done and inspected, not for work that has been promised. This has been how the company operates since 2008.
Do you handle Party Wall notices?
Yes, where the work requires them. Under the Party Wall etc. Act 1996, notifiable work on a shared wall needs 2 months written notice to the adjoining owner, while excavation near a neighbouring structure and building at the line of junction need 1 month. We serve the notices and manage the award process as part of the job.
Will I get certificates at the end?
Yes. Electrical work is tested and certificated under Part P, and building control issues a completion certificate where an application was required. You receive the handover pack — it is what a buyer's solicitor will ask for when you eventually sell.
How long will it take?
It depends entirely on scope, and we give a programme with the written quote rather than a guess on the phone. What we will not do is start a job we cannot resource, which is the usual reason a build stalls halfway through.
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