Larger home extensions: the neighbour consultation scheme

The larger home extension route lets you build a single storey rear extension deeper than the normal permitted development limit, up to 8 metres on a detached house and 6 metres on any other house, provided you tell the council first and your neighbours do not successfully object. It is a prior approval process under Class A of Part 1 of the general permitted development order, and it runs to 42 days.

It is not a planning application. The council is not assessing design, materials or the principle of extending. On a larger home extension prior approval its only question, and only if a neighbour objects, is the effect on the amenity of adjoining premises. That narrow remit is the whole value of the route.

What the route actually permits

The normal Class A limit for a single storey rear extension is 4 metres beyond the original rear wall for a detached house and 3 metres for any other house. The neighbour consultation scheme doubles those figures.

The other limits stay in place and catch people out.

• Maximum height of 4 metres overall.
• Maximum eaves height of 3 metres where any part of the extension is within 2 metres of the boundary of the curtilage.
• Single storey only. No balcony, veranda or raised platform.
• The extension must be to the rear, beyond the original rear wall, not to the side.
• Extensions and outbuildings together must not cover more than half the curtilage, excluding the ground area of the original house.
• Materials similar in appearance to the existing house.

The word original matters. It means the house as first built, or as it stood on 1 July 1948 if earlier. Every previous rear extension counts against your allowance, whoever built it, which is why the position on a house that has been extended before is its own question, covered in extending a house that has already been extended.

The route is not available on article 2(3) land, so conservation areas, National Parks, National Landscapes, the Broads and World Heritage Sites are out. It is not available for a listed building, and it does not apply to flats or maisonettes at all.

Making the notification

You send the council a notification, not an application form asking for permission, though most authorities take it through the same portal and charge a fee.

What has to go in:

1. A written description of the proposed development, including how far the extension projects beyond the original rear wall, its maximum height, and its eaves height.
2. A plan of the site showing the proposed development.
3. The addresses of all adjoining premises, including those to the rear.
4. Your contact address and, where you are content to receive it, an email address.

The addresses of adjoining premises are your responsibility, and getting them wrong is the commonest reason a notification is treated as invalid. Adjoining means sharing a boundary with the house's curtilage, including diagonally at a corner and including the property behind. Walk the boundary and write them down rather than working from memory.

Measure the projection from the original rear wall, not from the current back of the house. If there is already a conservatory or a small extension there, say so in the description and show it on the plan. Officers check this against their own records and a discrepancy stops the clock.

How the neighbour consultation period works

Once the notification is valid, the council writes to the owners and occupiers of every adjoining property. The letter describes the proposal and gives them 21 days to object.

Objections have to be about the impact on the amenity of adjoining premises. Loss of light, overshadowing, overbearing effect on a rear window or garden, loss of outlook. Those are within scope.

Plenty of other things are not, and neighbours send them anyway: dislike of the design, concern about property values, disputes about the boundary line itself, worries about construction noise, or the argument that the extension is simply too big. The officer has to filter those out.

If nobody objects within the 21 days, the council must notify you that you may proceed. If anybody does object, the council considers the amenity impact and decides whether to grant prior approval.

What the council may and may not consider

This is where the route differs sharply from a planning application, and where it is worth holding your ground.

The authority's assessment is confined to the impact on the amenity of adjoining premises. It cannot refuse because the extension is out of keeping with the street, because it would prefer a pitched roof, or because the rear garden would be smaller than local policy suggests. It cannot impose conditions about materials, landscaping or hours of work.

It can refuse prior approval where the amenity impact on an adjoining property is unacceptable. In practice the usual ground is loss of light or an overbearing effect on a habitable room window or a small garden, often assessed with a 45 degree line taken from the nearest neighbouring window.

A refusal is not the end. You can appeal, or you can apply for full householder planning permission for the same or a reduced extension, where the council will assess it on ordinary planning merits. Many householders go straight to a householder application when they know the neighbour relationship is difficult, because the wider assessment gives more room to negotiate. A short Planning Statement addressing amenity directly is worth having in that situation.

Handling an objection well

If a neighbour objects, you usually hear about it informally first. Use that.

Ask what specifically concerns them. Loss of light to a kitchen window is a different problem from loss of light to a bathroom, and the fix may be as simple as pulling the extension in half a metre from the boundary or reducing the eaves height on that side. A revised proposal normally means a fresh notification and another 21 days, which is still faster than an appeal.

Where the concern is overlooking from a rooflight or a high-level window, an obscure glazing commitment can settle it, though on a prior approval there is no condition mechanism to secure it. How those commitments are enforced when they are conditions is covered in obscure glazing conditions.

Do not start on site while an objection is live. Building in the middle of a consultation period is the fastest way to turn a planning question into an enforcement file.

The 42 day period and starting work

The council has 42 days from receipt of the valid notification to notify you of its decision.

You may begin when the council tells you prior approval is not required, when it grants prior approval, or when 42 days pass without it notifying you of its decision. That last route is real but it is the weakest position to build from, because a purchaser's solicitor will want evidence that the notification was valid and that the period had expired. Keep the submission receipt, the validation email and a note of the date.

Build exactly what you described. Deemed consent and express prior approval both attach to the particulars you submitted, and an extension 300 millimetres deeper than the notification is not permitted development.

Recording the development

Two administrative steps close the process and both get forgotten.

The developer must notify the council in writing when the development is completed, giving the address and the completion date. Do it, and keep the acknowledgement.

Then assemble the file a future buyer will ask for: the notification, the plans as submitted, the council's letter confirming you may proceed, the completion notification, and the building control completion certificate. A lawful development certificate is the only formal way to confirm that works are lawful, and if there is any doubt about the projection measurement or the original rear wall, applying for one now is far cheaper than resolving it during a sale.

Enter your postcode on PlanScope to see which documents an extension application would need if the prior approval route is not available.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.