Objecting to a larger home extension under prior approval
The neighbour consultation scheme gives you 21 days, and only amenity counts. Here is what the council may consider, how the projection is measured, and where objections fail.
You have 21 days from the date of the council's letter to object, and the letter is the only notice you will get. The larger home extension right lets a neighbour build a single storey rear extension deeper than the ordinary permitted development limits without applying for planning permission, provided the council runs a neighbour consultation first. If nobody objects, the council never looks at the effect on your house at all. If you do object, the council must consider the impact on the amenity of adjoining properties before it decides.
That is the whole mechanism. A larger home extension objection is not a planning application objection, and the difference in what the council may take into account is the thing most people get wrong.
What the right allows
Class A of Part 1 of Schedule 2 to the General Permitted Development Order 2015 permits enlargement of a house. The larger home extension provision allows a single storey rear extension projecting up to 8 metres beyond the original rear wall for a detached house and up to 6 metres for any other house, subject to a maximum height of 4 metres and, where the extension is within 2 metres of a boundary, a maximum eaves height of 3 metres.
Several limits sit alongside it. The extension must be single storey and at the rear. It must not extend beyond a side wall, must not include a veranda, balcony or raised platform, and the materials must be of similar appearance to the existing house. The right is not available on article 2(3) land, which covers conservation areas, National Parks, National Landscapes, the Broads and World Heritage Sites, and it can be removed anywhere by an article 4 direction.
It is also not available where the house is a flat or a maisonette, or where the building was not originally built as a house.
The neighbour consultation scheme in outline
The owner gives the council a written description of the proposal with the projection beyond the original rear wall, the maximum height and the eaves height, a plan of the site, and the addresses of the adjoining premises. The council then writes to the owners and occupiers of adjoining premises, giving 21 days to respond.
Adjoining means sharing a boundary, including at the rear. Someone two doors away does not get a letter, and their views carry no weight in this process even if they write in.
If no objection is received within the period, the development may go ahead. If an objection is received, the council has to consider the impact of the proposal on the amenity of all adjoining premises and decide whether to grant prior approval. The decision has to be made within 42 days of the council receiving the information, and if the council fails to decide in time the development may proceed.
What the council may consider once you object
Amenity, and only amenity, of adjoining premises. In practice that means loss of light to habitable room windows, overshadowing of the garden and the house, an overbearing or enclosing effect from a tall wall close to a boundary, and loss of outlook.
What the council may not consider is longer than most people expect. Design and appearance, materials beyond the similarity requirement, loss of a view, effect on property value, construction noise and disruption, boundary and party wall issues, drainage into your garden as a private matter, and the applicant's motives all fall outside. Objections built on those points are politely set aside, and an objection that mixes one good amenity point with five irrelevant ones reads weaker than the good point alone.
Write about light, overshadowing, enclosure and outlook, at specific windows and specific parts of the garden, at specific times of day. Our note on how daylight and sunlight assessments work explains the tests a professional would apply, and an overshadowing study is the document that shows shadow at different times of year. You are not expected to produce either, and knowing what they measure helps you describe the effect accurately.
Measuring the projection and the height yourself
Two measurements decide whether the right applies at all, and both are commonly got wrong.
The projection is measured from the original rear wall of the original house, meaning the house as first built or as it stood on 1 July 1948. If the neighbour already has a 3 metre extension and now proposes another 4 metres, the total from the original wall is 7 metres, which exceeds the 6 metre limit for a semi-detached or terraced house. That is not a matter of amenity. It means the proposal is not permitted development at all and needs a planning application.
Height is measured to the highest point of the extension, excluding a chimney or aerial, and the 3 metre eaves limit applies where any part is within 2 metres of the boundary. Measure from a fixed point and photograph your tape.
If you think a limit is exceeded, say so separately and clearly at the start of your response, because that is a different argument from amenity and the council has to be satisfied the proposal qualifies before it considers amenity at all.
Ground level differences
Sloping sites cause trouble. For these purposes height is measured from the surface of the ground immediately next to the building, and where the ground is not level the measurement is taken from the highest part of that surface. A house standing above its neighbour therefore gets its height measured from its own higher ground, and the resulting structure can be well above 4 metres as seen from the garden below.
That is lawful. It is also a legitimate amenity point, because the enclosing effect of a 4 metre wall built on ground a metre higher than yours is the effect the council should be assessing. Describe the level difference with a measurement and a photograph taken from your own side.
Timing, which is short
Twenty-one days runs from the date on the letter, not from the day you opened it. Respond in writing, by email so there is a record, quote the reference, and ask the council to confirm receipt. Keep it to one page with photographs attached.
If you are away when the letter arrives, send something short within the period and follow it with detail. A late objection may be considered if the council has not yet decided, and it does not have to be.
If the council grants approval anyway
Prior approval decisions are decisions, and the applicant can appeal a refusal. Third parties have no equivalent right of appeal, so the practical options are narrower. Where you believe the council made a procedural error, for example it failed to notify an adjoining occupier or decided before the 21 days expired, raise it with the council first and then consider the ombudsman route for maladministration.
Where the built extension does not match what was notified, that is a different matter entirely. The right is only available for what was described, so an extension built deeper or higher than the approved details is a breach of planning control and can be reported to the enforcement team.
And if the proposal turns into a planning application because the limits are exceeded, the range of considerations opens up. Design, overlooking, character and everything else becomes relevant, and you get another consultation period. Our guide to commenting on a planning appeal covers the stage after that.
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.
If you are the one extending rather than objecting, the 66 report types show which supporting documents a householder application needs. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
How long do I have to object to a larger home extension?
Twenty-one days from the date on the council's notification letter. Respond in writing, ideally by email so there is a record, quote the reference and ask for confirmation of receipt. A late response may be considered if the council has not yet decided, but there is no obligation on the authority to take it into account.
What can the council take into account?
Only the impact on the amenity of adjoining premises. That covers loss of light to habitable room windows, overshadowing of house and garden, an overbearing or enclosing effect, and loss of outlook. Design, materials, loss of a view, property value, construction disruption and boundary disputes are all outside the scope of this process.
How far can a neighbour extend under this right?
Up to 8 metres beyond the original rear wall for a detached house and up to 6 metres for any other house, single storey, with a maximum height of 4 metres and a maximum eaves height of 3 metres where the extension is within 2 metres of a boundary. The right is not available in conservation areas and other article 2(3) land.
Does an existing extension count towards the limit?
Yes. The projection is measured from the original rear wall of the house as first built or as it stood on 1 July 1948, not from the current rear wall. An earlier extension therefore eats into the allowance, and a proposal that exceeds the limit when measured properly is not permitted development at all and needs a planning application.
What if the ground levels differ between the two gardens?
Height is measured from the surface of the ground immediately next to the building, taken at its highest part where the ground is uneven. A house standing higher than yours measures from its own ground level, so the wall can be well above 4 metres seen from your side. That is lawful, and it is still a legitimate amenity point to raise.
Can I appeal if the council grants prior approval?
No. Only the applicant has a right of appeal, against a refusal. Where you believe the council made a procedural error, such as failing to notify an adjoining occupier or deciding before the 21 days expired, raise it with the council and then consider a complaint to the Local Government and Social Care Ombudsman about maladministration.
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.