Class A: new flats above detached blocks of flats

Class A permits up to two storeys of new flats above a qualifying purpose-built detached block of flats, subject to height, date, fire safety and prior approval requirements.

This permitted development right applies in England under Part 20 of Schedule 2 to the GPDO. Establish the current and historic building use, protected-land position and written prior approval before committing to a scheme.

Which block qualifies?

Class A applies to a purpose-built detached block of flats at least three storeys high above ground, built from 1st July 1948 to 5th March 2018 inclusive. It permits up to two additional storeys of new flats immediately above the existing topmost residential storey, on the principal part of the building. It cannot be used if the permission for the building’s dwellinghouse use was granted only by Part 3 Class M, MA, N, O, P, PA or Q.

Limits on the extension

The new roof must rise no more than 7 metres above the old roof and be no higher than 30 metres above ground level, disregarding plant for those roof-height tests. An additional storey’s internal floor-to-ceiling height cannot exceed the lower of 3 metres and the height of any storey of the principal part of the existing block. The proposed homes must be flats. Replacement or additional rooftop plant is allowed only if there is existing plant, and its height cannot exceed the specified existing plant height.

Structural strengthening is restricted to existing walls or foundations within the curtilage, along with permitted service works. Visible external supports are not permitted on completion. New access and ancillary storage or waste facilities must remain within the curtilage, with the latter kept behind the specified principal and highway-facing side walls.

Where the right is excluded

The site cannot be article 2(3) land, a site of special scientific interest, a listed building or land within its curtilage, a scheduled monument or land within its curtilage, a safety hazard area, a military explosives storage area, or land within 3 kilometres of an aerodrome perimeter. Article 2(3) land includes conservation areas, National Parks, the Broads, areas of outstanding natural beauty (National Landscapes) and World Heritage Sites. Check any Article 4 Direction and conditions on earlier permissions as well.

Prior approval issues

Prior approval addresses transport and highways; air traffic and defence assets; contamination and flood risk; external appearance; natural light in all habitable rooms of the new flats; the amenity of the existing building and neighbours, including overlooking, privacy and loss of light; and protected views where relevant.

Fire safety is an additional statutory issue. If the existing block is at least 18 metres high, external wall construction requires a professional report confirming compliance with Building Regulations requirement B4(1). Where the development meets the Part 20 fire risk condition, the authority also considers the fire-safety impacts on intended occupants, with a fire-safety statement and Health and Safety Executive consultation (replaced by Building Safety Regulator consultation from 21st October 2026 under SI 2026/1056) under Paragraph B. The fire risk condition is met where the post-development building has at least two dwellings and reaches 18 metres in height or seven storeys, measured under article 9A of the Development Management Procedure Order. The external-wall and new-building fire tests have different triggers.

Provide a construction-management report before starting, setting out working hours and mitigation of noise, dust, vibration and traffic for occupants and neighbours.

For Classes A to AD, provide a description, a scaled north-pointing site plan, scaled floor plans showing each new flat’s total floor space, room dimensions and use, windows, doors and walls, existing and proposed elevations, the number of new dwellings, and addresses of flats and other premises already in the building. A site-specific flood risk assessment is needed where Paragraph B requires Environment Agency consultation. The authority may seek reasonably necessary supporting assessments. Notices go to neighbours and relevant existing occupiers.

Every new home must meet the GPDO article 3(9A) minimum of 37 square metres gross internal area and the nationally described space standard. The development must be completed within three years from prior approval, and the local planning authority must be notified in writing of completion. The new dwellinghouses are subject to the statutory Class C3 use condition.

Application and decision

Apply for prior approval before work starts. Paragraph B sets out the application information, consultation and publicity procedure. The authority can refuse if eligibility is not demonstrated or if information is insufficient, and must refuse prior approval where adequate natural light is not provided in every habitable room of the proposed new dwellinghouses. Work must await a written notice granting prior approval; there is no automatic consent after 56 days. Approved plans and any reasonable conditions must be followed. Check the latest consolidated legislation before making a proposal.

Legislation and related guidance

Read Class A, A.1 and A.2 in the current legislation, together with Paragraph B and the eligibility table.

Class A legislation (checked 24th September 2026)

The following reproduces the consolidated Class A, A.1 and A.2 text as checked on 24th September 2026. Read the official Part 20 text for the legal source and any subsequent amendments. Contains public sector information licensed under the Open Government Licence v3.0.

Permitted development

A. Development consisting of works for the construction of up to two additional storeys of new dwellinghouses immediately above the existing topmost residential storey on a building which is a purpose-built, detached block of flats, together with any or all—

(a) engineering operations reasonably necessary to construct the additional storeys and new dwellinghouses;

(b) works for the replacement of existing plant or installation of additional plant on the roof of the extended building reasonably necessary to service the new dwellinghouses;

(c) works for the construction of appropriate and safe access to and egress from the new and existing dwellinghouses, including means of escape from fire, via additional external doors or external staircases;

(d) works for the construction of storage, waste or other ancillary facilities reasonably necessary to support the new dwellinghouses.

Development not permitted

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

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

(b) above ground level, the building is less than 3 storeys in height;

(c) the building was constructed before 1st July 1948, or after 5th March 2018;

(d) the additional storeys are constructed other than on the principal part of the building;

(e) 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 building;

(f) the new dwellinghouses are not flats;

(g) the height of the highest part of the roof of the extended building would exceed the height of the highest part of the roof of the existing building by more than 7 metres (not including plant, in each case);

(h) the height of the highest part of the roof of the extended building (not including plant) would be greater than 30 metres;

(i) development under Class A.(a) would include the provision of visible support structures on or attached to the exterior of the building upon completion of the development;

(j) development under Class A.(a) would consist of engineering operations other than works within the existing curtilage of the building to—

(i) strengthen existing walls;

(ii) strengthen existing foundations; or

(iii) install or replace water, drainage, electricity, gas or other services;

(k) in the case of Class A.(b) development there is no existing plant on the building;

(l) in the case of Class A.(b) development the height of any replaced or additional plant as measured from the lowest surface of the new roof on the principal part of the extended building would exceed the height of any existing plant as measured from the lowest surface of the existing roof on the principal part of the existing building;

(m) development under Class A.(c) would extend beyond the curtilage of the existing building;

(n) development under Class A.(d) would—

(i) extend beyond the curtilage of the existing building;

(ii) be situated on land forward of a wall forming the principal elevation of the existing building; or

(iii) be situated on land forward of a wall fronting a highway and forming a side elevation of the existing building;

(o) the land or site on which the building is located, is or forms part of—

(i) article 2(3) land;

(ii) a site of special scientific interest;

(iii) a listed building or land within its curtilage;

(iv) a scheduled monument or land within its curtilage;

(v) a safety hazard area;

(vi) a military explosives storage area; or

(vii) land within 3 kilometres of the perimeter of an aerodrome.

Conditions

A.2. —

(1) Where any development under Class A is proposed, development is permitted subject to the condition that before beginning the development, the developer must apply to the local planning authority for prior approval of the authority as to—

(a) transport and highways impacts of the development;

(b) air traffic and defence asset impacts of the development;

(c) contamination risks in relation to the building;

(d) flooding risks in relation to the building;

(e) the external appearance of the building;

(f) the provision of adequate natural light in all habitable rooms of the new dwellinghouses;

(g) impact on the amenity of the existing building and neighbouring premises including overlooking, privacy and the loss of light; …

(h) whether because of the siting of the building, the development will impact on a protected view identified in the Directions Relating to Protected Vistas dated 15 March 2012 issued by the Secretary of State, …

(i) where the existing building is 18 metres or more in height, the fire safety of the external wall construction of the existing building, ; and

(j) where the development meets the fire risk condition, the fire safety impacts on the intended occupants of the building

and the provisions of paragraph B (prior approval) of this Part apply in relation to that application.

(2) Any development under Class A is permitted subject to the condition that it must be completed within a period of 3 years starting with the date prior approval is granted.

(3) Any development under Class A is permitted subject to the condition that 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 occupiers of the building and adjoining owners or occupiers will be mitigated.

(4) The developer must notify the local planning authority of the completion of the development as soon as reasonably practicable after completion.

(5) The notification referred to in sub-paragraph (4) must be in writing and must include—

(a) the name of the developer;

(b) the address or location of the development; and

(c) the date of completion.

(6) Any new dwellinghouse created under Class A is to remain in use 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.

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Page updated: 2nd October 2026