The seven metre rule for two-storey rear extensions

If you are planning a two storey rear extension 7 metre boundary distance is the condition that decides whether you need permission. Class A of Part 1 of Schedule 2 to the General Permitted Development Order 2015 does not permit a rear extension of more than one storey where the enlarged part would come within 7 metres of any boundary of the curtilage that is opposite the rear wall of the house. Separately, a two-storey rear extension cannot project more than 3 metres beyond the original rear wall.

Both limits apply at once. Miss either and the extension needs a householder application, which is not a disaster, just a different timetable and a fee.

Why the rear boundary distance matters

The 7 metre figure exists to protect the garden behind yours. A two-storey rear wall close to a shared rear boundary blocks light and dominates the outlook from the neighbouring garden in a way a single-storey extension does not, and the order deals with that by keeping a buffer rather than by asking anyone to judge the impact.

The consequence is that the rule bites hardest on exactly the houses whose owners most want the space. Short gardens on post-war estates and Victorian terraces with 12 metre plots often cannot achieve 7 metres behind a two-storey extension at all.

Work out the distance before you pay for drawings. A tape measure and ten minutes saves a wasted design.

Measuring to an irregular rear boundary

The test refers to any boundary opposite the rear wall of the house, so the shortest distance governs. One corner within 7 metres removes the right for the whole extension.

Splayed and angled boundaries are where this goes wrong. A garden that narrows towards one corner can measure 8 metres on one side of the extension and 6.4 metres on the other, and the extension is then outside Class A even though most of it clears the limit. The same applies where the garden boundary steps, or where a rear access path cuts the corner off.

Three practical points:

• Measure from the proposed rear face of the extension, not from the existing rear wall
• Measure to the boundary itself, which may not be the fence line if the fence sits inside the title boundary
• Where a corner is marginal, measure it on site rather than scaling off a title plan, because land registry plans are indicative

The householder technical guidance published by the government shows the measurement conventions with diagrams, and it is the document an officer will reach for.

The three metre depth limit for two storeys

A rear extension of more than one storey can project at most 3 metres beyond the rear wall of the original dwellinghouse. "Original" means as built, or as it stood on 1 July 1948 for older houses, so a previous extension counts against your allowance even if you did not build it.

That matters on houses that already have a small rear addition. A Victorian terrace with an original back addition is a particular trap, because what looks like an obvious infill is often measured from a wall that was there in 1948.

Two further Class A limits catch two-storey work. The extension cannot exceed the height of the highest part of the existing roof, and where it comes within 2 metres of a boundary the eaves height is capped at 3 metres, which usually rules out a two-storey extension close to a side boundary.

Matching the roof pitch of the existing house

Class A carries a condition that where the enlarged part has more than one storey, or where the extension is to the side, the roof pitch of the enlarged part must, so far as practicable, be the same as the roof pitch of the original house.

"So far as practicable" leaves room for argument, and the argument usually concerns a hipped roof or an awkward junction. Where you cannot match the pitch, you are outside Class A and need permission, so the safer course on a marginal design is to apply for a lawful development certificate for proposed works under section 192 of the Town and Country Planning Act 1990 rather than build and hope.

Materials are a separate condition: the exterior must be of a similar appearance to the existing house. Similar, not identical, though a brick that reads as a different colour from across the garden will attract a complaint.

Window restrictions on the upper floor

Any window in a side elevation at first floor level or above has to be obscure-glazed, and non-opening unless the openable part is more than 1.7 metres above the floor of the room. That condition applies to the extension itself and is a common reason for retrospective trouble, because clear glazing goes in during the build and nobody checks.

Rear-facing windows are unrestricted under Class A, which is the quiet irony of the rule: the 7 metre buffer protects the garden behind while the windows looking into it face no restriction at all.

Rooflights are treated as part of the roof and have their own projection limit under Class C where they are added to an existing roof rather than formed in a new one.

Where the rule removes the right entirely

On article 2(3) land, which covers conservation areas, National Parks, National Landscapes, the Broads and World Heritage Sites, Class A does not permit a rear extension of more than one storey at all. The 7 metre question does not arise, because the right is not there.

Flats and maisonettes have no Part 1 rights of any kind, so any extension needs permission. Houses created by a prior approval conversion, for example under Class MA from commercial use, often have permitted development rights removed by condition, and the same applies where an Article 4 direction is in force. Our note on how a council makes an Article 4 direction explains how to find one.

Check the planning history as well. Conditions on an earlier permission frequently remove Class A rights on new estates, and the relevant decision notice may be twenty years old.

Plans that evidence the distance

Where the extension is within Class A, keep the evidence as though you will need it, because a buyer's solicitor will ask in due course.

Produce a dimensioned site plan showing the rear boundary, the proposed rear face and the measured distance at the closest point, a section through the extension and the garden, and dated photographs with a tape or staff visible. Keep the supplier's specification for the glazing in the side elevation.

Where permission is needed, the application is a householder one with an eight week determination period, and the case will turn on light, outlook and overlooking rather than on the 7 metre figure. A short planning statement dealing with the neighbouring garden and the daylight effect does more than an elevation drawing alone. If the works are already built, the enforcement time limits for operational development in England changed under the Levelling-up and Regeneration Act 2023, and the current position is in our note on enforcement time limits for permitted development breaches.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it, and remember that a lawful development certificate is the only formal way to confirm that works are lawful.

Enter your postcode on PlanScope to see which documents a householder application for a two-storey extension needs.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.