Class A — enlargement, improvement or other alteration of a dwellinghouse (extensions)

Class A – enlargement, improvement or alteration This provides permitted development rights for the enlargement, improvement or other alteration of a house. Under Class A the following limits and conditions apply: 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 M, N, P, PA or Q of Part 3 of this Schedule (change of use) Enlargement etc. is not permitted where the house was created under the permitted development rights to change use, set out in Classes M, N, P, PA, and Q of Part 3 of Schedule 2 to the Order (see page 4). (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) Extensions (including any extensions to the original house under Class A or under a separate planning permission) and other buildings must not exceed 50% of the curtilage. The 50% limit covers all buildings so will include existing and proposed outbuildings as well as any existing or proposed new extensions to a house. It will exclude the area covered by the original house but will include any later extensions or any separate detached buildings, even where they were built prior to 1948, or if the house was built after that date, built when the house itself was built (for example a detached garage or garden shed). In the diagram below, the maximum area that can be built on as permitted development, whether as an extension to the house or outbuildings erected under Class E, would be 50% of the white area. Curtilage of house Original house 11 (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 Any enlargement, improvement, or alteration to a house must not exceed the height of the highest part of the roof of the existing house. If it does, an application for planning permission will be required. The highest part of the roof of the existing house will be the height of the ridge line of the main roof (even though there may be other ridge lines at a lower level) or the height of the highest roof where roofs on a building are flat. Chimneys, firewalls, parapet walls and other protrusions above the main roof ridge line should not be taken into account when considering the height of the highest part of the roof of the existing house. However, when calculating the height of the enlarged part of the house, this measurement should be at the highest part of the enlargement and may include any protrusions above the roof such as parapet walls etc. (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 For the purpose of measuring height, the eaves of a house are the point where the lowest point of a roof slope, or a flat roof, meets the outside wall. The height of the eaves will be measured from the ground level at the base of the external wall of the extension to the point where the external wall would meet (if projected upwards) the upper surface of the roof slope. Parapet walls and overhanging parts of eaves should not be included in any calculation of eaves height. 12 The following example shows the side view of an extension with a pitched roof: Where there is a flat roof, a similar approach should be taken for measuring eaves: Eaves height is measured from ground level at the base of the outside wall to the point where that wall would meet the upper surface of the roof slope - the overhang should be ignored for the purposes of measurement. Roof of enlarged part of house Eaves height is measured from the ground level at the base of the outside wall to the point where that wall would meet the upper surface of the flat roof - the overhang and the parapet wall should be ignored for the purposes of measurement. Flat roof Parapet Wall 13 Where the existing house has eaves of different heights, then the restriction on the height of the eaves for the part of the house enlarged, improved or altered is measured against the highest level of eaves on the existing house. However, where a house is built on sloping ground, the height of the eaves on the existing house should be measured in terms of the elevation from which any extension of a house is to be made. The eaves of any extension can not be above the horizontal level of this line on this elevation of the house. The eaves of any extension can not be above the horizontal level of this line on this elevation of the house. 14 (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 This restriction means that any development to enlarge a house that is in front of a principal elevation, or in front of a side elevation that fronts a highway will require an application for planning permission. Principal elevation has the meaning set out in the ‘General Issues’ section of this document (see page 7). In this context, ‘extend beyond a wall’ comprises not only the area immediately in front of the wall, but also an area in front of a line drawn from the end of the wall to the boundary of the property. In the diagram below, neither extension shown would be permitted development - they both extend beyond a wall forming a principal elevation that fronts a highway. Original house These extensions would not be permitted development Any extension forward of this line would not be permitted development and will require an application for planning permission Boundary of property Highway Principal Elevation 15 The principal elevation could include more than one wall facing in the same direction - for example, where there are large bay windows on the front elevation, or where there is an ‘L’ shaped frontage. In such cases, all such walls will form the principal elevation and the line for determining what constitutes ‘extends beyond a wall’ will follow these walls. Any extension forward of this line will not be permitted development and will require an application for planning permission Bay windows form part of principal elevation Highway Any extension forward of this line will not be permitted development and will require an application for planning permission Highway Highway Walls Forming Principal Elevation Principal Elevation 16 If a house sits on a corner plot where a side elevation fronts a highway, there will be an additional restriction on permitted development to the side of the house. Original house These extensions would not be permitted development Any extension forward of these lines at the front of the house and and between the side of the house and the highway will not be permitted devePD technical guidance, Class A · official source →