Larger Home Extension – up to 6m or 8m

The Larger Home Extension provisions are part of Class A of Part 1 of the GPDO. They can allow a deeper single-storey rear enlargement than the normal 3 or 4 metre limit, but only if the proposal satisfies the Class A rules and the paragraph A.4 prior approval procedure is completed before development begins.

For a qualifying house, the maximum rear projection can be up to 8 metres for a detached house or 6 metres for any other house, measured from the relevant rear wall of the original dwellinghouse.

If the extension does not exceed the ordinary 3 or 4 metre rear limit, see our Rear Extensions guide instead.

How much larger can the extension be?

The larger-home provisions in paragraph A.1(g) apply to a single-storey enlargement which goes beyond the normal paragraph A.1(f) rear depth but remains within the larger maximum:

• Detached house: more than 4 metres and up to 8 metres beyond the relevant original rear wall.
• Any other house: more than 3 metres and up to 6 metres beyond the relevant original rear wall.

The enlarged part must not exceed 4 metres in overall height, and all the other relevant Class A limits still apply.

Where the Larger Home Extension provisions do not apply

Paragraph A.1(g) is not available where the dwellinghouse is on article 2(3) land or on a Site of Special Scientific Interest.

Class A itself is also unavailable in some cases, including flats and maisonettes, houses created only by the Part 3 classes listed in A.1(a), and dwellinghouses built under Part 20. A planning condition or Article 4 direction can also remove the relevant permitted development right.

See the main Class A guide for the wider restrictions and the meaning of the original dwellinghouse.

The 42-day prior approval procedure

You must notify the local planning authority before beginning development. The information required by paragraph A.4 includes a written description of the proposal, the rear projection, maximum height and eaves height, a plan showing the site and proposed development, details of any existing enlargement to which the proposal will be joined, the addresses of adjoining premises and the developer’s contact details.

The local planning authority can refuse at an early stage if it considers that the proposal does not comply with the Class A limitations or that insufficient information has been provided to establish compliance.

If the application proceeds, the authority must notify each adjoining owner or occupier and give them an opportunity to make representations. Where an adjoining owner or occupier objects, the authority must consider the impact of the proposed development on the amenity of adjoining premises and decide whether prior approval should be granted.

The development must not begin until one of the events in A.4(10) has occurred: written confirmation that prior approval is not required, written prior approval, or expiry of the statutory 42-day period without the authority notifying the developer whether prior approval is given or refused.

What if nobody objects?

If no adjoining owner or occupier objects, the amenity prior approval test in A.4(7) is not triggered. However, you should still wait for the relevant A.4(10) event before starting work. The procedure is not simply a neighbour vote: the proposal must still comply with the underlying Class A limitations.

What counts as an adjoining premises?

The notification requirement is concerned with adjoining premises. In practice, this can include premises sharing a boundary with the application site, including to the side or rear. The application information should identify the addresses of adjoining premises so the local planning authority can serve the required notices.

There is an application fee

An application fee is payable to the local planning authority. Rather than quoting a figure here, see our planning application fees page for the current amount.

Existing and joined extensions

This is one of the most important parts of the current Class A wording. Where the proposed enlargement will be joined to an existing enlargement of the original dwellinghouse, paragraph A.1(ja) can require the total enlargement to remain within the relevant limits.

Paragraph A.4 also requires the application information to describe the total enlargement where the proposed work will be joined to an existing enlargement. A pre-existing extension can therefore affect both whether the proposal is permitted development and what must be shown in the prior approval submission.

If an existing enlargement already projects beyond the original rear wall, you cannot simply measure a fresh 6 or 8 metres from the back of that later extension. The relevant measurement is from the original rear wall, and the joined enlargement must remain within the statutory maximum.

Can a Larger Home Extension also be a side extension?

Potentially, yes. A single-storey enlargement can extend beyond a side elevation and also extend beyond a rear wall. In that situation, the side-extension restrictions in A.1(j) and the rear-extension restrictions in A.1(g) both apply.

So a proposal which relies on the larger rear depth must still be single-storey, no more than 4 metres high and, where it extends beyond a side-elevation wall, no wider than half the width of the original dwellinghouse at its widest point. A side elevation that fronts a highway can also prevent the enlargement under A.1(e).

This is why a deep side or wrap-around extension needs to be assessed as one geometric proposal rather than being labelled simply “side” or “rear”.

Can you do more than one Larger Home Extension?

There is no useful shortcut based simply on submitting separate applications. Each proposed enlargement must be assessed against the Class A wording that applies to the development actually proposed, including A.1(ja) where enlargements are joined.

Physically separate enlargements may be capable of being assessed separately, while joined enlargements can have to be assessed together. If you are proposing multiple extensions, show the full relationship clearly on the plan and test each relevant Class A limitation before relying on permitted development.

Other Class A limits still apply

• The total area of ground covered by buildings must remain within the 50% curtilage rule.
• If any part of the enlargement is within 2 metres of a curtilage boundary, eaves height is restricted to 3 metres.
• The enlargement cannot extend beyond the principal elevation or beyond a side-elevation wall that fronts a highway.
• Materials must be of a similar visual appearance to the existing dwellinghouse, subject to the wording of A.3.
• The enlargement cannot include a verandah, balcony or raised platform under Class A.

After prior approval

Where prior approval is required, the development must be carried out in accordance with the approved details. Where prior approval is not required, or the 42-day provision applies, the development must be carried out in accordance with the information submitted unless the local planning authority and developer agree otherwise in writing.

Permitted development deals only with planning permission. Building Regulations may still be required, and the Party Wall etc. Act 1996 may also apply depending on the works.

If CIL may be relevant, see our CIL guide before starting development.

Also see the government Permitted development rights for householders – Technical Guidance. It is helpful for diagrams and interpretation, but always check the current GPDO because the guidance predates some later amendments.

Larger Home Extension legislation

Class A – enlargement, improvement or other alteration of a dwellinghouse

Permitted Development

A. The enlargement, improvement or other alteration of a dwellinghouse.

Development not permitted

A.1 Development is not permitted by Class A if—

(a) permission to use the dwellinghouse as a dwellinghouse has been granted only by virtue of Class G, M, MA, N, P, PA or Q of Part 3 of this Schedule (changes of use);

(b) as a result of the works, the total area of ground covered by buildings within the curtilage of the dwellinghouse (other than the original dwellinghouse) would exceed 50% of the total area of the curtilage (excluding the ground area of the original dwellinghouse);

(c) the height of the part of the dwellinghouse enlarged, improved or altered would exceed the height of the highest part of the roof of the existing dwellinghouse;

(d) the height of the eaves of the part of the dwellinghouse enlarged, improved or altered would exceed the height of the eaves of the existing dwellinghouse;

(e) the enlarged part of the dwellinghouse would extend beyond a wall which—
(i) forms the principal elevation of the original dwellinghouse; or
(ii) fronts a highway and forms a side elevation of the original dwellinghouse;

(f) subject to paragraph (g), the enlarged part of the dwellinghouse would have a single storey and—
(i) extend beyond the rear wall of the original dwellinghouse by more than 4 metres in the case of a detached dwellinghouse, or 3 metres in the case of any other dwellinghouse, or
(ii) exceed 4 metres in height;

(g) for a dwellinghouse not on article 2(3) land nor on a site of special scientific interest, the enlarged part of the dwellinghouse would have a single storey and—
(i) extend beyond the rear wall of the original dwellinghouse by more than 8 metres in the case of a detached dwellinghouse, or 6 metres in the case of any other dwellinghouse, or
(ii) exceed 4 metres in height;

(h) the enlarged part of the dwellinghouse would have more than a single storey and—
(i) extend beyond the rear wall of the original dwellinghouse by more than 3 metres, or
(ii) be within 7 metres of any boundary of the curtilage of the dwellinghouse being enlarged which is opposite the rear wall of that dwellinghouse;

(i) the enlarged part of the dwellinghouse would be within 2 metres of the boundary of the curtilage of the dwellinghouse, and the height of the eaves of the enlarged part would exceed 3 metres;

(j) the enlarged part of the dwellinghouse would extend beyond a wall forming a side elevation of the original dwellinghouse, and would—
(i) exceed 4 metres in height,
(ii) have more than a single storey, or
(iii) have a width greater than half the width of the original dwellinghouse;

(ja) any total enlargement (being the enlarged part together with any existing enlargement of the original dwellinghouse to which it will be joined) exceeds or would exceed the limits set out in sub-paragraphs (e) to (j);

(k) it would consist of or include—
(i) the construction or provision of a verandah, balcony or raised platform,
(ii) the installation, alteration or replacement of a microwave antenna,
(iii) the installation, alteration or replacement of a chimney, flue or soil and vent pipe, or
(iv) an alteration to any part of the roof of the dwellinghouse; or

(l) the dwellinghouse is built under Part 20 of this Schedule (construction of new dwellinghouses).

A.2 In the case of a dwellinghouse on article 2(3) land, development is not permitted by Class A if—

(a) it would consist of or include the cladding of any part of the exterior of the dwellinghouse with stone, artificial stone, pebble dash, render, timber, plastic or tiles;

(b) the enlarged part of the dwellinghouse would extend beyond a wall forming a side elevation of the original dwellinghouse; or

(c) the enlarged part of the dwellinghouse would have more than a single storey and extend beyond the rear wall of the original dwellinghouse.

(d) any total enlargement (being the enlarged part together with any existing enlargement of the original dwellinghouse to which it will be joined) exceeds or would exceed the limits set out in sub-paragraphs (b) and (c).

Conditions

A.3 Development is permitted by Class A subject to the following conditions—

(a) the materials used in any exterior work (other than materials used in the construction of a conservatory) must be of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse;

(b) any upper-floor window located in a wall or roof slope forming a side elevation of the dwellinghouse must be—
(i) obscure-glazed, and
(ii) non-opening unless the parts of the window which can be opened are more than 1.7 metres above the floor of the room in which the window is installed; and

(c) where the enlarged part of the dwellinghouse has more than a single storey, or forms an upper storey on an existing enlargement of the original dwellinghouse, the roof pitch of the enlarged part must, so far as practicable, be the same as the roof pitch of the original dwellinghouse.

A.4—(1) The following conditions apply to development permitted by Class A which exceeds the limits in paragraph A.1(f) but is allowed by paragraph A.1(g).

(2) Before beginning the development the developer must provide the following information to the local planning authority—
(a) a written description of the proposed development including—
(i) how far the enlarged part of the dwellinghouse extends beyond the rear wall of the original dwellinghouse;
(ii) the maximum height of the enlarged part of the dwellinghouse; and
(iii) the height of the eaves of the enlarged part of the dwellinghouse;
(iv) where the enlarged part will be joined to an existing enlargement of the dwellinghouse, the information in sub-paragraphs (i) to (iii) must be provided in respect of the total enlargement (being the enlarged part together with the existing enlargement to which it will be joined);

(b) a plan indicating the site and showing the proposed development and any existing enlargement of the original dwellinghouse to which the enlarged part will be joined;

(c) the addresses of any adjoining premises;

(d) the developer’s contact address; and (e) the developer’s email address if the developer is content to receive communications electronically. together with any fee required to be paid.

(3) The local planning authority may refuse an application where, in the opinion of the authority—
(a) the proposed development does not comply with, or
(b) the developer has provided insufficient information to enable the authority to establish whether the proposed development complies with, the conditions, limitations or restrictions applicable to development permitted by Class A which exceeds the limits in paragraph A.1(f) but is allowed by paragraph A.1(g).

(4) Sub-paragraphs (5) to (7) and (9) do not apply where a local planning authority refuses an application under sub-paragraph (3) and for the purposes of section 78 (appeals) of the Act such a refusal is to be treated as a refusal of an application for approval.

(5) The local planning authority must notify each adjoining owner or occupier about the proposed development by serving on them a notice which—
(a) describes the development by setting out the information provided to the authority by the developer under paragraph A.4(2)(a);
(b) provides the address of the proposed development;
(c) specifies the date when the information referred to in sub-paragraph (2) was received by the local planning authority and the date when the period referred to in sub-paragraph (10)(c) would expire; and
(d) specifies the date (being not less than 21 days from the date of the notice) by which representations are to be received by the local planning authority.

(6) The local planning authority must send a copy of the notice referred to in sub-paragraph (5) to the developer.

(7) Where any owner or occupier of any adjoining premises objects to the proposed development, the prior approval of the local planning authority is required as to the impact of the proposed development on the amenity of any adjoining premises.

(8) The local planning authority may require the developer to submit such further information regarding the proposed development as the authority may reasonably require in order to determine the application.

(9) The local planning authority must, when considering the impact referred to in sub-paragraph (7)—
(a) take into account any representations made as a result of the notice given under subparagraph (5); and
(b) consider the amenity of all adjoining premises, not just adjoining premises which are the subject of representations.

(10) The development must not begin before the occurrence of one of the following—
(a) the receipt by the developer from the local planning authority of a written notice that their prior approval is not required;
(b) the receipt by the developer from the local planning authority of a written notice giving their prior approval; or
(c) the expiry of 42 days following the date on which the information referred to in subparagraph (2) was received by the local planning authority without the local planning authority notifying the developer as to whether prior approval is given or refused.

(11) The development must be carried out—
(a) where prior approval is required, in accordance with the details approved by the local planning authority;
(b) where prior approval is not required, or where sub-paragraph (10)(c) applies, in accordance with the information provided under sub-paragraph (2), unless the local planning authority and the developer agree otherwise in writing.

(12) The local planning authority may grant prior approval unconditionally or subject to conditions reasonably related to the impact of the proposed development on the amenity of any adjoining premises.

(16) When computing the number of days in sub-paragraph (5)(d), any day which is a public holiday must be disregarded.

 

Does the 45-degree rule apply to a larger home extension?

 

Do not confuse the neighbour-consultation prior approval test with a council’s local 45-degree rule. A 45-degree test is not one of the national dimensions in Class A of the GPDO. It is normally local design or amenity guidance used when a proposal needs planning permission.

Where local guidance is relevant, the council should actually apply it rather than merely mention it. R (Bronwen Manby) v Mayor and Burgesses of the London Borough of Hackney [2026] EWHC 1543 (Admin) confirms that point. But the guidance remains guidance: different councils use different methods, and passing or failing the test is not automatically decisive.

See our main guide to rear extensions and our separate guide explaining how the 45-degree rule fits into planning decisions.

 

Larger Home Extension Page Updated: 27th August 2026