Prior approval drawings for a larger home extension cost from £375 drawings + £150 survey (£525 total) at Fixed Fee Plans, and your council charges £249 on top. That buys the survey, the scaled plans and the written description the Order asks for, so your council can run its 42-day process on a 6m extension, or 8m on a detached house.
The route sits halfway between ordinary permitted development and a full householder application. You notify rather than apply, your neighbours get a say on one question only, and the paperwork is lighter than either. It still fails on a wrong depth or a missing address, and both come from measuring the house properly.
What does the fee cover, and what goes to the council?
Our fee covers the survey and the drawings; the council's fee goes to the council and is never part of ours. The split, to scale:
The figure that trips people up is depth. Paragraph A.1(ja) of Class A counts any earlier extension that the new one joins, so a 3m kitchen extension from the 1990s plus a new 3m room is a 6m enlargement. On a semi-detached house that is the limit. We measure from the rear wall of the house as first built, and the description we write gives the total, which is what the council checks.
Which houses can use the larger home extension route?
Houses outside conservation areas and other article 2(3) land can use it, for a single-storey rear extension only. Flats and maisonettes cannot, and nor can a house whose rights were removed by an article 4 direction or a planning condition. If any of those apply, the route is a householder application instead.
Two London patterns come up often. Many inner boroughs are largely conservation area, so the route is closed for a whole street. And post-war semi-detached houses in the outer boroughs often already carry a rear extension, which uses up part of the 6m. Our permitted development checker answers the first question in a minute, and it will tell you plainly if your extension needs no notification at all.
What happens once the council has the notification?
The council writes to the adjoining neighbours, waits at least 21 days for comments, and then has until day 42 to decide. If nobody objects, it only checks the extension against the Class A limits. If a neighbour objects, it also weighs the effect on the amenity of the adjoining homes, and nothing else.
Across London, the 33 planning authorities decided 4,547 larger home extension notifications in the year to June 2026, and 3,478 of them could go ahead (MHCLG live table PS1). Refusals vary widely by borough: Harrow refused 106 in that year and Camden one, which is why we read your council's recent decisions before drawing a proposal close to a boundary.
When is a householder application the better route?
When the extension is deeper than 6m (8m detached), taller than 4m, more than one storey, or on article 2(3) land, prior approval cannot cover it and a householder application is the route. Our complete planning drawing service is £645 drawings + £150 survey (£795 total), and the council's householder fee is £548.
Whichever route you take, building regulations approval is separate. The structure, insulation and drainage of a 6m extension go to building control on their own drawings, which are £545 drawings + £150 survey (£695 total) from us. A long rear extension usually needs a steel beam where the old rear wall opens up, sized by structural calculations. The larger home extension guide sets out every paragraph of Class A with its source.
Frequently asked questions
How long does larger home extension prior approval take?
Up to 42 days from the day the council receives a complete notification. If the council has not given its decision by then, the extension may go ahead under paragraph A.4(10). Our survey is usually booked within five working days.
Can my neighbour stop a 6m extension?
A neighbour cannot veto it. An objection makes the council assess the effect on the adjoining homes' amenity, and the council can refuse on that ground alone. Most London notifications in the year to June 2026 could go ahead, but the share varies by borough.
Do I need a certificate of lawfulness as well?
Not for the extension itself: the council's written decision, or the passing of 42 days, is the record. Some buyers' solicitors ask for more, and a certificate of lawfulness is from £545 drawings + £150 survey (£695 total) if you want one.
Can I start building before the 42 days are up?
Only if the council has already written to say prior approval is not required or is granted. Starting earlier, even with your neighbours' agreement, means building without the permission the route gives.