Planning Portal

PPS 7 (Addendum): Residential Extensions and Alterations
Annex A: Context and Design

A4 An extension or alteration to a residential property should be designed to become an integral part of the property both functionally and visually. Such works should not be designed in isolation solely to fit in a required amount of accommodation. Proposals that are badly sited or designed, or that are incompatible with their surroundings, can lead to an undesirable change in the character of the existing property and the area in which they are located. Success depends upon striking the right balance between adaptation and sensitivity to the original design.
A5 The overall aim is to encourage high quality design solutions irrespective of whether the approach followed seeks to mirror the style of the existing property or adopts a contemporary modern design approach. To ensure good design any extension or alteration will need to complement the host building and respect its location and wider setting.   
A6 An extension or alteration should not be so large or so prominent as to dominate the host property or its wider surroundings, rather development proposals should be in scale with existing and adjoining buildings. All such works should have proportion and balance, fitting in with the shape of the existing property. The height, width and general size of an extension should generally be smaller than the existing house and subordinate or integrated so as not to dominate the character of the existing property, although it is accepted that on occasion a larger extension may be required - for example to facilitate the renovation and upgrading of a small rural dwelling to meet modern amenity standards. It will not usually be appropriate to allow an extension to project above the ridge line of the existing dwelling and this will be especially important where uniform building height is part of the street scene.
A7 Proposals in an urban context should not overdevelop the site in terms of massing, plot size and proximity to boundaries thereby, for example, creating a visual ‘terrace’ effect. This is one of a number of problems associated with side extensions, where they can alter the character of the area by filling the visual gaps between residential properties. The need for adequate space along side boundaries is also important to provide ease of access to the rear of the property and to allow for maintenance. This will also serve to eliminate the possibility of any part of the extension, including rainwater goods, overhanging neighbouring property.
A8 A further concern may arise where a side extension to a semi-detached dwelling is proposed at the same height and follows the same building line as the block comprising an original pair of dwellings. This will often compromise the appearance and architectural integrity of the block, and if repeated throughout a neighbourhood is likely to have an adverse impact upon the character of the wider area. To address this particular problem, proposals of this nature should be ‘set back’ from the building line or front of the house and also ‘set down’ from the ridge line.
A9 Extensions or alterations to the front of a property require great care as the front elevation is often the most visible to public view. Poor design can upset the architectural integrity of the existing property and have an intrusive effect on the street scene. It is important, therefore, to ensure that extensions and alterations to the front of property do not detract from the street scene, especially where there is a clear and visually obvious ‘building line’ or architectural features. In such cases they should appear to be part of the existing property and not an obvious addition. This can be achieved by ensuring any such works are in proportion with the property, its fenestration and detailing, with matching materials, roof design and pitch.
A10 Alterations or an extension to a dwelling should not infringe upon a neighbour’s property. For example, it is an infringement of a neighbour’s property rights should foundations or guttering encroach onto their land or if an extension overhangs or attaches to their property. Where an extension abuts or runs close to a property boundary, permission to enter neighbouring land will also be required to enable approved works to be carried out or for future maintenance purposes. Consequently, it is advisable to discuss proposals with any neighbours before submitting a planning application. It should be noted that infringement of property rights is primarily a legal matter between the relevant parties.
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