You might have questions such as ‘What size side extension can I build without planning permission?’ or ‘Do I need to ask the council before building the side extension’ – this page will answer those questions. You can build a rear extension or even a larger home extension at the same time, but please don’t be tempted to build a wraparound extension as this is likely to fall foul of the regulations.
You can erect a side extension on houses and bungalows, but not flats. You are limited to 50% width of the property. If you want a double storey extension this will require planning permission. You do not need to consult with the local authority before you build the side extension (bar building regs), but if you are unsure why not book a Zoom session with Ian, the founder of Planning Geek. Although you are able to obtain a certificate of proposed development. Please contact us if this is of interest.
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 extension if asked prior to permitted development. This has been overturned at appeal many times.
Can you have a side extension on both sides?
Yes you can. A client recently approached us after they had been refused a certificate of lawfulness for a side extension on both sides of a dwelling. This is inaccurate.
In appeal APP/R5510/X/13/2207335 from 2014, the Inspectorate, Graham Self, said “The appellant’s interpretation of the GPDO is correct. As was stated in an appeal decision on a similar proposal in Essex in 2010,1 the phrase “the enlarged part” refers back to the opening words in Class A (“the enlargement….of a dwellinghouse”), and sub-paragraph A.1(h) is written in the singular. In their stated reason for refusal, the council have altered words in the GPDO to make them plural (“enlarged parts” and “side elevations”), but the singular wording of sub-paragraph A.1 indicates that each enlarged part is to be considered individually. The extensions would not be physically attached to each other.”
The appeal was granted and a certificate of lawfulness issued.
If you need our assistance with any appeal, then please contact us for a free and without obligation fee proposal.
Any restrictions or Article 4s?
Before starting work check to see if there any conditions that have been placed on your property which might prevent building a side 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.
Once you have built your side 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. It is worth reading through the Permitted development rights for householders Technical Guidance issued by the government for assistance with not so straightforward extensions such as those properties with outriggers and those on corner plots etc.
Note that the permitted development right of side 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 side extensions.
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. You also cannot build a side extension if the building is listed, in a conservation area, AONB, Broads or Heritage site. They might also have been removed as a result of an Article 4 or a condition on a previous planning application.
Finally side 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 will also not be able to build a side extension where a highway is to the side if the property – in other words a corner plot. You might however be able to erect an outbuilding there, such as a garage.
You have said where we can’t – so what can we do?
Glad you asked! The criteria for a side extension is quite simple.
Single Storey Extensions
Double Storey Extensions
The 50% restriction includes any outbuildings, so beware of any garages or large sheds, or even decking etc.
Class A – enlargement, improvement or other alteration of a dwellinghouse
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).
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.
Page Updated: 4th September 2023