How long does planning permission take for an extension?
The legal target is eight weeks from the day your application is validated, for the householder application most extensions need. In practice, budget nine to twelve weeks from the day you press submit — and considerably longer if your house is listed or in a conservation area.
The clock does not start when you submit
This is the single fact that catches people out. The eight-week period runs from validation, not from the moment you pay the fee and upload your drawings. Validation is the council checking that the application is complete: the right forms, a location plan, existing and proposed elevations, the correct fee. If anything is missing, the application sits in a queue and the clock never starts.
On a well-prepared submission, validation takes a few days to a couple of weeks depending on how busy the planning department is. On a scrappy one, it can drag on while officers write back asking for a document you forgot. So the gap between “I submitted” and “the eight weeks began” is entirely within your control — get the application right first time and you shave weeks off the whole thing.
The stages, and how long each one takes
| Stage | Typical duration | Whose time it is |
|---|---|---|
| Drawings and documents prepared | 2–6 weeks | You and your designer — not council time |
| Validation | A few days to 2 weeks | Council; the eight weeks starts when this finishes |
| Neighbour and public consultation | At least 21 days | Runs inside the eight weeks |
| Householder application decision | 8 weeks from validation | The statutory target |
| Major application decision | 13 weeks from validation | Rarely relevant to one house |
| Larger home extension prior approval | 42 days from validation | The faster permitted-development route |
| Lawful Development Certificate | 8 weeks from validation | Confirms you did not need permission |
Statutory periods are set by article 34 of the Town and Country Planning (Development Management Procedure) (England) Order 2015, with detail from Planning Portal and GOV.UK guidance. Durations for drawings and validation are typical, not fixed.
What eats up the eight weeks
Most of that period is not officers staring at your plans. A chunk of it is the consultation window: the council notifies your immediate neighbours and, where relevant, posts a site notice, then waits at least 21 days for comments. Only after that does the case officer weigh everything up, sometimes visit the site, and write a recommendation.
Objections are the usual cause of a slow decision. A neighbour raising concerns about overlooking, loss of light or the effect on the street does not automatically sink your application, but it does mean the officer has to address each point, which takes longer than nodding through an uncontested rear extension. So does anything that pulls in a specialist consultee — a tree officer, a highways engineer, a conservation officer.
The honest headline is that the system mostly works. English councils decided about 93% of householder applications within eight weeks or an agreed extended period in the year to March 2026, and roughly nine in ten were granted. The eight-week failures tend to be the awkward cases, not the ordinary single-storey extension.
The extension of time agreement
Somewhere around week six, many applicants get an email asking them to agree an “extension of time” — a new, later decision date. It has to be in writing, and it is the council's way of buying a fortnight or so when a decision will not quite land inside eight weeks.
Agreeing is usually the sensible move. Refuse, and you keep your right to appeal against non-determination, but you also risk the officer issuing a quick refusal simply to hit the deadline rather than a considered approval a week later. Most people sign it. If your officer is asking for a second or third extension with no clear reason, that is the point to push back and ask what the hold-up is.
The faster routes, and when they apply
If your extension is permitted development, you may not need a full application at all. The larger home extension prior approval route lets you build a deeper single-storey rear extension — up to 8m on a detached house, 6m otherwise — on a 42-day decision. The council notifies your neighbours; if none objects within 21 days, or the council does not decide within the 42 days, you can build. It is faster than a full application and cheaper, but it only covers that specific type of extension.
If you are building under ordinary permitted development and want proof for a future buyer, apply for a Lawful Development Certificate. It carries the same eight-week statutory period as a planning application but a lower fee, and it gives you a document confirming the work was lawful. For what actually counts as permitted development in the first place, see the permitted development rules for extensions.
If the council misses the deadline, or says no
Miss the deadline with no agreed extension and you gain a right to appeal to the Planning Inspectorate for non-determination — though in practice, chasing your case officer usually gets a decision faster than an appeal, which can take months. For a non-major application left undetermined after 16 weeks with no extension agreed, you are also entitled to a refund of the application fee.
If you are refused, a householder appeal has a tight deadline: it must reach the Planning Inspectorate within 12 weeks of the date on the decision notice, far shorter than the six months you get for most other appeals. Often the quicker fix is to talk to the officer about why it was refused and submit a revised application — you get one free resubmission within twelve months of the decision on the same site.
Once you do have permission, you are not under pressure to build straight away. A full planning permission normally lasts three years; you have to begin the work within that window, after which it can carry on.
How to shave weeks off the process
The biggest single lever is a clean, complete application, so validation is quick and the clock starts sooner. Good drawings matter here as much as good design — see what drawings you need and who should draw them. Pre-application advice from the council, paid for upfront, can flush out objections before the formal clock starts, which is worth it on anything ambitious or in a sensitive location. And a quiet word with the neighbours before they receive a formal consultation letter heads off a surprising number of objections. The householder planning application fee in England is £548 from 1 April 2026; pre-application advice is charged separately and varies by council.
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