Rear residential extensions
You might have questions such as ‘What size rear extension can I build without planning permission?’ or ‘Do I need to ask the council before building the rear extension’ – this page will answer those questions. If you are looking at an extension greater than 3m or 4m then check out the larger home extension where you might be able to extend up to 8m.
You can erect a rear extension on houses and bungalows, but not flats. You are limited to 3m on a terraced or semi-detached property or 4m on a detached property for a single storey rear extension. A double storey extension is limited to 3m.
All these permissions are contained within Part 1 of the GPDO and apply to dwelling houses. The definition for dwellinghouses contained within Article 2 of the GPDO says “does not include a building containing one or more flats, or a flat contained within such a building;” Therefore a dwelling house ought to apply to both C4 and sui generis dwellinghouses. However there have been examples of local authorities refusing an rear extension if asked prior to permitted development. This has been overturned at appeal many times.
Before starting work check to see if there any conditions that have been placed on your property which might prevent building a rear extension. These are quite common on new build properties or maybe as a result of a previous planning approval. In those cases full planning permission might be required relevant to that condition or restriction for your extension.
As long as you comply with the rules, you do not need to seek permission before you build. Once you have built your rear extension enjoy it or you can choose to submit an optional application for a Lawful Development Certificate (LDC) which might be useful when you come to sell the property.
Note that the permitted development right of rear extensions does not remove the need to have both building regs and Party Wall agreements.
If you are in a CIL area check this important information for extensions.
Outriggers! / Wraparound Extension
Be careful if your property has an outrigger. A what? No, nothing to do with external rigging on a ship! An outrigger was more common on Victorian properties and might contain the kitchen and I suspect the original outside toilet! Of course this might be known as something else in your part of the world (the Victorian extension – not the toilet!). Whatever you call it, you need to be careful.
If you wish to build within the L shape and perhaps put an extension on the lounge out, this will be a side extension as you are building onto a side elevation. As a result you will be limited to a single storey and up to 50% of the width of the property.
Another important limitation is whilst it is possible to put an extension onto the side of the outrigger, as a side extension, it is vital that the rear of this does not either extend beyond 3m from a rear wall of the house. In the example below there are 3 rear walls. Or 6m if you also submit a larger home extension before construction. This can be confusing, so please feel free to book a Zoom session with Ian, the founder of Planning Geek to check on your particular rear extension.
The actual rear elevation for your extension will be quite narrow and can only go on the actual rear elevation.
In most cases it is not possible to create a wraparound extension by combining both a rear and a side extension due to this limit on side extensions. Due to the way that the rules are written, the part at the rear will be considered a side extension and not a rear extension.
For this wraparound extension you will need to opt for planning permission.
If you are unsure as to whether you extensions comply with the limits, feel free to book a Zoom session with Ian, the founder of Planning Geek.
Where else can’t we benefit?
These permissions do not apply to flats or maisonettes. Nor do they apply to houses that have been converted from agricultural buildings, storage, light industrial, shops or casinos. They do however apply to houses (not flats) converted from offices under Class O. If the building is listed, in a conservation area, AONB, Broads or Heritage site you can’t build a two storey rear extension, but a single storey rear extension might be possible – check below for restrictions. Your rights for Class A might also have been removed as a result of an Article 4 or a condition on a previous planning application.
Finally extensions are from the original building or as it was on 1st July 1948. In other words, you can’t extend an extension to the full amounts mentioned below if the property has already used up part or all of the allowance since it was built or if added after 1st July 1948. If the extension was built prior to 1948, then you can extend it again. Knowing whether the extension was original or been built by a previous owner is key.
You have said where we can’t – so what can we do?
Glad you asked! The answer depends as to whether you have a detached or a semi-detached/terraced house. But let’s go through each type of extension in turn…….
Note that it is possible to extend a previous extension, but the combined extensions must comply with all the criteria below. Note that the original extension could have been via full planning or permitted development.
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Single Storey Extensions – up to 3m depth for a terrace or semi-detached house
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Double Storey Extensions – up to 3m depth on a detached, terrace or semi-detached house
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Despite the various restrictions, you can build quite a large side or rear extension as long as your garden is large enough. The 50% restriction includes any outbuildings, so beware of any garages or large sheds etc.
Also see Permitted development rights for householders – Technical Guidance
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.
Rear Extensions Page Updated: 21st August 2023