Class AA – enlargement of a dwellinghouse by construction of additional storeys
The General Permitted Development Order (GPDO) has given the ability to add additional storeys in the airspace to many homes by one or two additional storeys.
You may add up to two additional storeys where the existing house consists of two or more storeys or one additional storey where the property consists of one single storey or a bungalow.
As with any new permitted development rights there are situations where it does not apply! Oh and some rules to stick to in the application as you might expect. Of course there is no guarantee that your foundations were even designed to take an additional storey or two, so take the advice of a structural engineer seriously.
The most up to date version of the legislation is below.
Where can’t we benefit from this permission?
They do not apply to houses that have been converted from offices under Class O, nor conversions under Class G, Class MA, agricultural buildings, storage, light industrial, shops or casinos. You cannot build up if your property is in on Article 2(3) land, which is in a conservation area, AONB, Broads, National Park or Heritage site, nor on an SSSI
They might also have been removed as a result of an Article 4 or a condition on a previous planning application. If the property was built before 1st July 1948 or after 28th October 2018 then I’m afraid this is also not available.
If the property has already been extended upwards, then you do not get a second chance, even if you had full planning. In theory you could do this on a listed building, subject to the criteria below about the design of the principal elevation, although you would need listed building consent!
Finally this right for additional storeys does not apply where the building contains one or more flats. If the property has one or more flats, check out Part 20. In particular check out our easy reference table to see which airspace opportunities apply to which type of properties.
You have said where we can’t – so what can we do?
Glad you asked!
You may extend upwards by the additional storeys on a detached property, subject to a prior approval application, up to a maximum height of 3.5m on a bungalow or single storey property or up to 7m where the existing house consists of two or three storeys. These measurements are the highest part of the house that are permitted. If the property is a semi-detached or in a terrace then you are limited to 3.5m above the other property or the highest part of the terrace on any building.
The height of the upwards extensions is also limited by the factor that it can’t exceed that of any existing floor to ceiling height or 3m, whichever is the lower. Finally you must only extend the principal part of the house upwards and any strengthening works required must be within the boundaries of your own property and those works cannot be visible on the outside of the property.
So far, I think I comply – so what next?
In any construction there are some items you can’t do. For example the materials must be of a similar appearance to the rest of the house, and you can’t add any windows to a side elevation including the roof, which must be the same pitch as the existing roof. Once constructed you can only use this for a C3 dwellinghouse. This will eliminate the future conversion to a C4 under Class L. You can potentially split this into flats, but you would require planning permission to do this.
So how do I apply or can I do this tomorrow?
Unlike some other extensions, you can’t just start work tomorrow! You must apply via a Prior Approval to the local authority for the additional storeys who will consider several elements. This includes the impact on any adjoining property including overlooking, privacy and the loss of light. The design of the property on the principal elevation and that of any side fronting a highway.
If you are in a zone that might affect air traffic then this will be a consideration and finally whether the new storeys would affect a protected view. You will also need to inform the local authority how you will mitigate against disturbance to the neighbours and the hours of any construction which must be completed within three years of any successful prior approval application.
When you do apply you must supply drawings showing the elevations and any windows etc.
Class AA – enlargement of a dwellinghouse by construction of additional storeys
AA. The enlargement of a dwellinghouse consisting of the construction of—
(a) up to two additional storeys, where the existing dwellinghouse consists of two or more storeys; or
(b) one additional storey, where the existing dwellinghouse consists of one storey,
immediately above the topmost storey of the dwellinghouse, together with any engineering
operations reasonably necessary for the purpose of that construction.
Development not permitted
AA.1. Development is not permitted by Class AA if—
(a) permission to use the dwellinghouse as a dwellinghouse has been granted only by virtue of Class G, M, MA, N, O, P, PA or Q of Part 3 of this Schedule (changes of use);
(b) the dwellinghouse is located on—
(i) article 2(3) land; or
(ii) a site of special scientific interest;
(c) the dwellinghouse was constructed before 1st July 1948 or after 28th October 2018;
(d) the existing dwellinghouse has been enlarged by the addition of one or more storeys above the original dwellinghouse, whether in reliance on the permission granted by Class AA or otherwise;
(e) following the development the height of the highest part of the roof of the dwellinghouse would exceed 18 metres;
(f) following the development the height of the highest part of the roof of the dwellinghouse would exceed the height of the highest part of the roof of the existing dwellinghouse by more than—
(i) 3.5 metres, where the existing dwellinghouse consists of one storey; or
(ii) 7 metres, where the existing dwellinghouse consists of more than one storey;
(g) the dwellinghouse is not detached and following the development the height of the highest part of its roof would exceed by more than 3.5 metres—
(i) in the case of a semi-detached house, the height of the highest part of the roof of the building with which it shares a party wall (or, as the case may be, which has a main wall adjoining its main wall); or
(ii) in the case of a terrace house, the height of the highest part of the roof of every other building in the row in which it is situated;
(h) the floor to ceiling height of any additional storey, measured internally, would exceed the lower of—
(i) 3 metres; or
(ii) the floor to ceiling height, measured internally, of any storey of the principal part of the existing dwellinghouse;
(i) any additional storey is constructed other than on the principal part of the dwellinghouse;
(j) the development would include the provision of visible support structures on or attached to the exterior of the dwellinghouse upon completion of the development; or
(k) the development would include any engineering operations other than works within the curtilage of the dwellinghouse to strengthen its existing walls or existing foundations.
AA.2.—(1) Development is permitted by Class AA subject to the conditions set out in sub-paragraphs (2) and (3).
(2) The conditions in this sub-paragraph are as follows—
(a) the materials used in any exterior work must be of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse;
(b) the development must not include a window in any wall or roof slope forming a side elevation of the dwelling house;
(c) the roof pitch of the principal part of the dwellinghouse following the development must be the same as the roof pitch of the existing dwellinghouse; and
(d) following the development, the dwellinghouse must be used as a dwellinghouse within the meaning of Class C3 of the Schedule to the Use Classes Order and for no other purpose, except to the extent that the other purpose is ancillary to the primary use as a dwellinghouse.
(3) The conditions in this sub-paragraph are as follows—
(a) before beginning the development, the developer must apply to the local planning authority for prior approval as to—
(i) impact on the amenity of any adjoining premises including overlooking, privacy and the loss of light;
(ii) the external appearance of the dwellinghouse, including the design and architectural features of—
(aa) the principal elevation of the dwellinghouse, and
(bb) any side elevation of the dwellinghouse that fronts a highway;
(iii) air traffic and defence asset impacts of the development; and
(iv) whether, as a result of the siting of the dwellinghouse, the development will impact on a protected view identified in the Directions Relating to Protected Vistas dated 15th March 2012 issued by the Secretary of State;
(b) before beginning the development, the developer must provide the local planning authority with a report for the management of the construction of the development, which sets out the proposed development hours of operation and how any adverse impact of noise, dust, vibration and traffic on adjoining owners or occupiers will be mitigated;
(c) the development must be completed within a period of 3 years starting with the date prior approval is granted;
(d) the developer must notify the local planning authority of the completion of the development as soon as reasonably practicable after completion; and
(e) that notification must be in writing and include—
(i) the name of the developer;
(ii) the address of the dwellinghouse; and
(iii) the date of completion.
Procedure for applications for prior approval
AA.3.—(1)The following sub-paragraphs apply where an application to the local planning authority for prior approval is required by paragraph AA.2(3)(a)
(2) The application must be accompanied by—
(a) a written description of the proposed development, including details of any works proposed;
(b) a plan which is drawn to an identified scale and shows the direction of North, indicating the site and showing the proposed development; and
(c) a plan which is drawn to an identified scale and shows—
(i) the existing and proposed elevations of the dwellinghouse, and
(ii) the position and dimensions of the proposed windows.
together with any fee required to be paid.
(3) The local planning authority may refuse an application where, in its opinion—
(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, any conditions, limitations or restrictions specified in paragraphs AA.1 and AA.2.
(4) Sub-paragraphs (5) to (8) 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 proposed development, including the maximum height of the proposed additional storeys;
(b) provides the address of the proposed development; and
(c) specifies the date, which must not be less than 21 days from the date the notice is given, by which representations are to be received by the local planning authority.
(6) Where the application relates to prior approval as to the impact on air traffic or defence assets, the local planning authority must consult any relevant operators of aerodromes, technical sites or defence assets and where appropriate the Civil Aviation Authority and the Secretary of State for Defence.
(7) Where an aerodrome, technical site or defence asset is identified on a safeguarding map provided to the local planning authority, the local planning authority must not grant prior approval contrary to the advice of the operator of the aerodrome, technical site or defence asset, the Civil Aviation Authority or the Secretary of State for Defence.
(8) Where the application relates to prior approval as to the impact on protected views, the local planning authority must consult Historic England, the Mayor of London and any local planning authorities identified in the Directions Relating to Protected Vistas dated 15th March 2012 issued by the Secretary of State.
(9) The local planning authority must notify the consultees referred to in sub-paragraphs (6) and (8) specifying the date by which they must respond, being not less than 21 days from the date the notice is given.
(10) When computing the number of days in sub-paragraphs (5)(c) and (9), any day which is a public holiday must be disregarded.
(11) The local planning authority may require the developer to submit such information as the authority may reasonably require in order to determine the application, which may include—
(a) assessments of impacts or risks;
(b) statements setting out how impacts or risks are to be mitigated, having regard to the National Planning Policy Framework issued by the Ministry of Housing, Communities and Local Government in July 2021; and
(c) details of proposed building or other operations.
(12) The local planning authority must, when determining an application—
(a) take into account any representations made to them as a result of any notice given under sub-paragraph (5) and any consultation under sub-paragraph (6) or (8); and
(b) have regard to the National Planning Policy Framework issued by the Ministry of Housing, Communities and Local Government in July 2021, so far as relevant to the subject matter of the prior approval, as if the application were a planning application.
(13) The development must not begin before the receipt by the applicant from the local planning authority of a written notice giving their prior approval.
(14) The development must be carried out in accordance with the details approved by the local planning authority.
(15) The local planning authority may grant prior approval unconditionally or subject to conditions reasonably related to the subject matter of the prior approval.
Interpretation of Class AA
AA4.—(1) For the purposes of Class AA—
“defence asset” means a site identified on a safeguarding map provided to the local planning authority for the purposes of a direction made by the Secretary of State in exercise of the powers conferred by article 31(1) of the Procedure Order or any previous powers to the like effect;
“detached”, in relation to a dwellinghouse, means that the dwellinghouse does not—
(a) share a party wall with another building; or
(b) have a main wall adjoining the main wall of another building;
“principal part”, in relation to a dwellinghouse, means the main part of the dwellinghouse excluding any front, side or rear extension of a lower height, whether this forms part of the original dwellinghouse or is a subsequent addition;
“semi-detached”, in relation to a dwellinghouse, means that the dwellinghouse is neither detached nor a terrace house;
“technical sites” has the same meaning as in the Town and Country Planning (Safeguarded Aerodromes, Technical Sites and Military Explosives Storage Areas) Direction 2002;
“terrace house” means a dwellinghouse situated in a row of three or more buildings, where—
(a) it shares a party wall with, or has a main wall adjoining the main wall of, the building on either side; or
(b) if it is at the end of a row, it shares a party wall with, or has a main wall adjoining the main wall of, a building which fulfils the requirements of paragraph a.
(2) In Class AA references to a “storey” do not include—
(a) any storey below ground level; or
(b) any accommodation within the roof of a dwellinghouse, whether comprising part of the original dwellinghouse or created by a subsequent addition or alteration, and accordingly, references to an “additional storey” include a storey constructed in reliance on the permission granted by Class AA which replaces accommodation within the roof of the existing dwellinghouse.
Page Updated:22nd March 2023