Planning permission for extensions.

When you need it, and what removes permitted development.

Reviewed August 2026

The short answer

Many extensions are permitted development and need no application. The limits are strict, they apply to houses not flats, and a previous owner's extensions count. A condition or an Article 4 direction can remove the right. Check that first.

In practice · Weedon

A car port made into a room

The clearest way to explain a householder extension is to watch one go through it.

The order of work

01Read the permissionRights already removed by condition.

02Look under the roofSpace enclosed before anything new.

03Full applicationThe only route left open.

04Consent, then buildBuilding Regulations, then site.

A contemporary house in a wooded plot at Weedon in Northamptonshire, timber clad on a stone plinth, its first floor cantilevered over an open undercroft for parking. We designed it, and it was finished around 2017. Years later its new owners came back to make more of it.

The job

Site: A contemporary house in a wooded plot, Weedon, Northamptonshire
Role: Architect and planning agent, concept to working drawings
Consent: West Northamptonshire Council ref WND/2022/0152, householder permission, 26 May 2022
Outcome: A studio under the cantilever and a matching car port, built

What they wanted was space they already had. Enclosing the undercroft made a light filled room with two desks, a window seat to the garden and a new rear entrance, and a detached two bay car port in matching timber replaced the parking.

There was no permitted development route to any of it. The permission that allowed the house in the first place had removed the householder rights that would ordinarily cover an addition this size, so even a modest one needed a full application. That is the sentence most people never read on their own consent.

It was submitted in February 2022 and granted on 26 May with no objections, the period extended by agreement while the council cleared a backlog. Building Regulations approval followed in August, and the studio and car port have been built.

The arithmetic is the lesson. That room cost a wall, a floor and insulation. The roof, the structure and the foundations were paid for when the house was built. On most houses the cheapest square metres are the ones already under the roof.

The enclosing wall had no freedom to move. The balcony above it is uninsulated, so the new wall had to line up exactly with the structure overhead, and the window seat had to be positioned so the rear door did not take the best of the garden view with it. A rendered finish was chosen rather than new timber, which would have sat awkwardly against cladding that had weathered for five years.

Removing permitted development rights by condition is common on a one off house, and the reason is usually that the authority wanted a say in how a distinctive building was later altered. It is not a penalty. It does mean the first question on any extension is not what the rules allow in general, but what this particular property still has.

The proof

Four extensions, four routes.

Two storey · built

The Woods, Napton

A double storey rear extension to a cottage in a hilltop Warwickshire village with its own neighbourhood plan and a design guide to match. Brick, to sit with the cottage beside it. Decided by an officer under delegated powers rather than at committee, and since built.

Stratford-on-Avon District Council ref 18/03445/FUL · granted 4 February 2019

Prior approval · 8 metres

The White House, Shrewley

A single storey rear extension eight metres deep on a detached house, taken by the larger home extension route instead of a planning application. The council notified the adjoining neighbours, none of them objected, and it determined that prior approval was not required.

Warwick District Council ref W/20/0076 · prior approval, 25 February 2020

Linking extension · granted

Newbold Beeches, Leamington

A detached coach house standing separately in the grounds of a large Leamington villa, brought into the main house by a two storey linking extension so that the two read and work as one dwelling. Well beyond anything permitted development would carry.

Warwick District Council ref W/25/1184 · full permission granted, 27 November 2025

Revised · granted

Nursery Road, Edgbaston

A two storey side and forward extension withdrawn by the agent, redesigned, and consented six months later as a two storey side extension with a porch and a detached garage. Withdrawing is not losing. It keeps the decision in the applicant's hands.

Birmingham City Council refs 2007/07175/PA and 2008/01132/PA · withdrawn January 2008, granted July 2008

Every planning application we make in our own name is a matter of public record on a council register. Of the entries that carry a full description of the work, eighty are householder extensions granted, across nine planning authorities, the earliest of them in 1991.

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The first step

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01 · Where you stand

First, find out what you already have

Permitted development is a national grant of planning permission that already exists. Before anything is drawn, the question is whether this particular property still has it, because a great many do not.

It applies to houses, and the order is blunt about that: a dwellinghouse does not include a building containing one or more flats, or a flat inside one. A flat or a maisonette has no householder rights at all. Nor, in some cases, does a home created by a change of use under one of the prior approval routes.

The allowance is measured against the original house, which means the house as it stood on 1 July 1948, or as first built if it went up later. Every enlargement since counts against it, including the ones a previous owner built and never mentioned. On designated land, meaning a conservation area, a National Park, a National Landscape, the Broads or a World Heritage Site, side extensions and anything above one storey to the rear are out.

And the right can simply be taken away. A condition on an earlier permission removes it, which is common on a recently built one off house. An Article 4 direction removes it too, and it can cover a single property as readily as a whole street or area. A direction is made precisely because the council wants to see the applications.

Checking is cheap, and it is the first hour of the job rather than the last. The council's planning register lists the permissions on the property and the conditions attached to each of them. Article 4 directions are published by the council that made them. The policies map shows whether the site is on designated land. None of the three costs anything to look at.

Listing is a separate matter again, because it reaches the interior as well as the exterior, and no permitted development right is much use for an extension to a listed building. If any of these apply, the answer is not that the work cannot happen. It is that it goes by application, and the case has to be made rather than measured.

02 · The routes

Four ways an extension gets permission

Almost every extension arrives by one of four routes. Which one applies is a question about the property and the size of the work, and it is settled before the design starts.

Route 01

Permitted development

The national grant, and no application. A single storey rear extension may project four metres from the original rear wall on a detached house and three on any other house, and everything else standing in the curtilage must cover under half the land around the original house.

Where it fails: any two storey work to the side or the front needs an application.

Route 02

Larger home extension

A single storey rear extension of up to eight metres on a detached house, or six on any other house, on land that is not designated. Notify the council first. It writes to the adjoining neighbours, and only if one of them objects does it judge the effect on their amenity.

Where it fails: notice comes before work, not after, and the route is closed on designated land.

Route 03

Householder application

The full route, and the one most extensions above the limits take. Eight weeks from the day after the council holds a valid application, judged against national and local planning policy rather than against a table of dimensions, so design, neighbour amenity and character all come into it.

Where it fails: nothing here is measured. A scheme that fits the metres can still be refused on its effect.

Route 04

Lawful development certificate

Not a permission but a ruling. It asks the council to certify that what is proposed would be lawful, and once granted that lawfulness is conclusively presumed unless something material changes before the work begins. Optional, and quietly valuable.

Where it fails: it settles lawfulness only, and says nothing about whether the design is any good.

03 · The clock

What happens in the eight weeks

The statutory period for a householder application is eight weeks, beginning the day after the council receives a valid application. Valid is doing most of the work in that sentence: the application counts as received only once the form, the drawings, the certificates, everything on the authority's own published validation list and the fee are all in.

Nothing about the eight weeks is a promise. Nationally, ninety-three per cent of householder decisions in the year to March 2026 were made inside eight weeks or the time agreed, which is a softer statement than ninety-three per cent in eight weeks, and the difference is where most of the waiting lives.

If the answer is no, the deadline to appeal is twelve weeks from the date on the decision notice, not the six months that applies to other appeals, and it is an easy one to miss.

A householder appeal runs on a simplified written procedure. Neither side files fresh evidence at the appeal stage, so the case the inspector reads is the case that was in front of the council. That is worth knowing before the application goes in rather than after it comes back.

The alternative to appealing is applying again with a changed scheme, which is often the quicker of the two. It is no longer free: the concession that allowed one further application at no charge was abolished on 6 December 2023.

For scale, ninety per cent of householder applications in England were granted in the year to March 2026, and householder work made up fifty-one per cent of all planning decisions. It is the best trodden path in the system, which is a reason for confidence rather than complacency.

04 · The other permissions

Planning is not the only permission

Building Regulations approval is a separate consent, and the government's own guidance puts it in as many words: building regulations approval is different from planning permission, and you might need both. An extension needs it whether or not it needed planning permission. Without it there are no compliance certificates when the house is sold.

Approval comes either from the local authority's building control department or from a registered building control approver. It covers structure, fire, drainage, ventilation and insulation, and it is checked on site as the work goes up rather than settled on paper at the start.

The Party Wall etc. Act 1996 is separate again and is not planning at all. Work to a shared wall needs at least two months' notice to the neighbour. Excavating near their building needs at least one month. Neither notice asks permission. Both start a process that ends in an award if the neighbour does not simply agree.

Then the site specific ones. A protected tree, a bat roost in a roof or an eaves void, a listed building or a conservation area: each carries its own consent, notice or survey, and each is found by looking rather than by hoping.

Order matters more than people expect. A Building Regulations problem that surfaces late, a party wall notice served the week before the builder arrives, or a bat survey that can only be done in summer, all spend time the planning programme has already spent once. Sequencing them is most of what a good programme is.

Common questions

Extensions, answered

What does a householder planning application cost?

The council's fee in England is £548 for an application to extend or alter one house.

That figure applies from 1 April 2026 and it is national, so it is identical at every council. It buys a decision rather than a permission: a refusal is a determination and the fee is not returned. Prior approval for a larger home extension is charged at £249, and a certificate for proposed lawful development at half the full application fee. Applying online adds the Planning Portal's own service charge on top. What a practice charges to design the thing and run the application is a separate question entirely, and the fees guide linked at the foot of this page covers it.

Can a neighbour's objection stop an extension?

Not on its own. An objection carries weight when it raises a planning matter and none at all when it does not.

The council has to publicise the application, and where it does that with a site notice the notice stays up for at least twenty-one days. What the officer then weighs is the effect on light, outlook, privacy and the character of the area. Loss of a view, disruption during the build, a boundary dispute and an effect on property value are not planning matters, and a well written officer report will say so. Numbers do not decide it either, although a large number of objections can send an application to committee rather than to an officer. A conversation with the neighbours before the letters land is worth more than anything written afterwards.

Is a loft conversion covered by the same rules?

No. Additions to a roof are their own class, with a volume allowance rather than a projection limit.

The allowance is forty cubic metres for a terrace house and fifty for anything else, measured against the original roof space, and any earlier roof enlargement comes off it. Nothing may rise above the highest part of the existing roof, and nothing may extend beyond the roof plane of the principal elevation where that faces a highway. On designated land the right is not available at all. Building Regulations approval is needed whichever planning route applies, because a loft in use as a room is habitable space, and that brings fire escape, structure and insulation with it.

Does an extension have to match the house?

Under permitted development, broadly yes: the materials must be of a similar appearance to the existing house. Conservatories are the exception.

Similar appearance is not the same as identical, and it is judged on how the finished thing reads. Upper floor windows in a side elevation have a separate condition of their own: they must be obscure glazed, and non opening below 1.7 metres from the floor of the room. On a full application none of this is a rule at all, and a deliberate contrast is often the better answer. A rendered or glazed addition that reads as plainly new can sit more comfortably against weathered brick or timber than a poor imitation of it.

My house is listed. What is different?

Listed building consent is a separate consent, needed as well as planning permission, and it covers the inside as well as the outside.

Listing catches the whole building, and often separate structures standing in its grounds. Carrying out work that affects the character of a listed building without consent is a criminal offence rather than a planning irregularity, and it does not become lawful with the passage of time in the way an unauthorised extension eventually can. For an extension the practical consequence is that there are really two applications, prepared together and decided together, and the heritage case has to be made rather than asserted.

Could an extension attract a Community Infrastructure Levy charge?

Rarely, but it is worth checking. The levy bites at a hundred square metres or more of new floorspace.

Most extensions are well under that and are exempt without anyone having to do anything. Above it, a residential extension can still be exempt, but that exemption has to be claimed from the collecting authority and granted before development starts, and a claim made after the builder arrives is too late. Not every authority charges the levy, and the rate varies where they do. It is the kind of thing nobody expects on a domestic job, which is exactly why it catches people.

What happens if an extension is built without permission?

The council can take enforcement action, and in England it now has ten years in which to do it.

The single ten year limit took effect on 25 April 2024. For building work the clock runs from substantial completion, and where that completion happened before 25 April 2024 the older four year limit still applies instead. Deliberately concealing a breach can defeat the limit altogether, because the council may ask a magistrates court for a planning enforcement order and act after the period has run. The commoner consequence is quieter and arrives later: no compliance certificate, an awkward question from a buyer's solicitor, and a retrospective application made under pressure.

Written by

Rickett Architects

A RIBA Chartered practice, working since 1970, with more than 2,500 projects behind it. Our senior architects take projects from first survey through planning to completion, for private clients, developers and landowners across the Midlands and well beyond it.

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