The larger home extension prior approval and neighbour notice
Up to eight metres for a detached house, six for a semi or terrace. What the notice must contain, who gets consulted, and why silence from neighbours settles it.
The larger home extension prior approval lets you build a single storey rear extension deeper than the ordinary permitted development limits, provided you tell the council first and your neighbours do not successfully object. Up to eight metres for a detached house, up to six for a semi or terrace. The council writes to the adjoining owners, they get 21 days to object, and if nobody does, the council cannot refuse. That last sentence is the part most people miss.
The depths, the heights and which houses qualify
The scheme applies only to single storey rear extensions on houses. Flats are excluded, and so is anything above ground floor level.
| House type | Standard Class A depth | Larger home extension depth |
|---|---|---|
| Detached | Up to 4 metres | Over 4 and up to 8 metres |
| Semi-detached or terraced | Up to 3 metres | Over 3 and up to 6 metres |
Three dimensional limits apply throughout. Maximum height of 4 metres. Where any part of the extension is within 2 metres of the boundary of the curtilage, the eaves height must not exceed 3 metres. And the extension must not extend beyond a side wall of the original house.
The wider Class A conditions still bite. Materials of similar appearance to the exterior of the existing house. No verandah, balcony or raised platform. And the total ground area covered by buildings within the curtilage, excluding the original house, must not exceed half the curtilage once the original house footprint is deducted.
The scheme does not apply on article 2(3) land, so conservation areas, National Parks, National Landscapes, the Broads and World Heritage Sites are out. Nor does it apply to listed buildings. Original means the house as built or as it stood on 1 July 1948, so an earlier rear extension counts against your depth.
What you send, and what the council does with it
You give the council written notice before starting. The notice has to contain a written description of the proposal, stating how far the extension projects beyond the rear wall of the original house, its height at the eaves and its maximum height. It also needs a plan of the site showing the proposed development, the addresses of the adjoining premises, and your contact address including an email address if you have one. A fee is payable, and the current amount is on the Planning Portal fee schedule.
The council then notifies the owners or occupiers of the adjoining premises. Adjoining means sharing a boundary, so that is the properties either side and any behind you, and it can include a flat above a neighbouring shop. The notification describes the proposal, gives the address, and states the date by which representations must be received.
Councils may also put up a site notice or serve notice directly, and some do both. What they cannot do is consult the world at large and treat every response as an objection: only representations from adjoining owners or occupiers count.
The 21 day window
Adjoining owners and occupiers have 21 days from the date of the notification to object. The clock is on the council's letter.
If no representations are received in that period, the council may not refuse. The development may proceed, subject to the conditions of the class. That is an unusual position in English planning, and it is why the depth allowance is worth pursuing even where a neighbour is grumbling verbally: unless they write in, their view does not enter the process.
If representations do arrive, the position changes and the council must consider the impact of the extension on the amenity of adjoining premises. Objections about the loss of a view, property values, boundary disputes, construction noise or the neighbour's opinion of the design carry no weight, because the scheme confines the assessment to amenity impact on adjoining premises.
It is worth speaking to the neighbours before the notice goes in. A drawing shown across the fence, with the depth marked on the ground, prevents more objections than any amount of correspondence afterwards.
What the council may consider, and what it may not
Amenity of adjoining premises means the practical effects of the extension on the neighbouring properties: loss of light to habitable room windows, overbearing effect and enclosure, and overshadowing of the neighbour's garden or rear windows.
The council may not consider design, materials beyond the similar appearance condition, highway matters, drainage, ecology, the effect on the wider street scene, or any other planning issue. If a refusal notice cites those, it is open to challenge.
Where the amenity case is arguable, evidence helps. A simple shadow study at the equinox and in midsummer, or an Overshadowing Study showing the extent of shadow cast on the neighbour's garden through the day, answers the question the council is actually asking. So does a section drawing taken through the boundary showing the 45 degree line from the centre of the neighbour's nearest habitable window.
Small design changes often resolve it. Pulling the extension in from the boundary. Dropping the eaves. Replacing a flat roof at 3 metres with a lower mono-pitch. Setting the deepest part away from the neighbour's principal windows.
The 42 days, and the effect of silence
The council must determine within 42 days beginning with the day after it received the notice. Three outcomes are possible.
It notifies you that prior approval is not required, and you may build. It grants prior approval, and you may build in accordance with it. Or it refuses prior approval, in which case you can appeal to the Planning Inspectorate, or apply for full planning permission, or build within the standard Class A depth instead.
If the 42 days pass with no decision, the development may proceed. Do not rely on that without evidence: keep the submission receipt, the fee payment record and the date the council confirmed the notice was received. And check the class conditions, because silence does not cure a proposal that never qualified, and an extension that exceeds the depth or the eaves height gains nothing from the council's inaction.
Do not start work before the earlier of the council's notification and the expiry of the 42 days. Starting early takes the development outside the class.
Records, completion and what comes next
The class requires the development to be completed within a set period after the date the notice was received, so the approval does not sit on the shelf indefinitely. Check the current wording before assuming you have unlimited time, and tell the council in writing when the work is finished if the class or the council's letter asks for it.
Keep a file. The notice you gave, the plan, the council's letter, the neighbour notification dates and the decision. If the house is sold, a buyer's solicitor will ask for evidence that a large rear extension was lawful, and a prior approval letter is much easier to produce than a retrospective argument.
Building Regulations are a separate approval and always apply. Party wall matters under the Party Wall etc. Act 1996 are separate again, are civil rather than planning, and a boundary wall or foundations near the line usually trigger them.
Where prior approval is refused, a full householder application is the fallback and a short Planning Statement dealing with amenity, design and the local design guide is usually the only supporting document needed. Browse the full report list if the site has trees, flooding or heritage constraints that push the requirements wider.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. A lawful development certificate is the only formal way to confirm that works are lawful. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Enter your postcode on PlanScope to see which documents an extension application is likely to need.
Frequently asked questions
How deep can a larger home extension be?
Over four and up to eight metres beyond the rear wall for a detached house, and over three and up to six metres for a semi-detached or terraced house. Maximum height is four metres, and where any part sits within two metres of the boundary the eaves must not exceed three metres. Earlier rear extensions count against the depth.
What happens if no neighbour objects?
The council may not refuse. If no representations are received from adjoining owners or occupiers within the 21 day period, the development may proceed subject to the conditions of the class. Verbal grumbling does not count, so a neighbour who never writes in has not objected for the purposes of the scheme.
What can the council consider if a neighbour objects?
Only the impact of the extension on the amenity of adjoining premises: loss of light to habitable room windows, overbearing effect and enclosure, and overshadowing of the neighbour's garden or rear windows. Design, materials, highways, drainage, ecology and the street scene are outside the assessment.
How long does the council have to decide?
Forty two days beginning with the day after it received the notice. If that period passes without a decision, the development may proceed. Keep the submission receipt, the fee payment record and the council's acknowledgement, because silence does not cure a proposal that never qualified under the class.
Does the scheme apply in a conservation area?
No. The larger home extension route does not apply on article 2(3) land, which covers conservation areas, National Parks, National Landscapes, the Broads and World Heritage Sites, nor to listed buildings. In those locations a rear extension beyond the standard Class A depth needs a full planning application.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.