1. The front of the proposed extension should be set behind the building line of the main dwelling in order to achieve a visual break in the line of the building frontage. With two storey or first floor flank extensions, in order to decrease the possibility of "terracing", a minimum gap of 1 metre from the common boundary with the adjoining dwelling should be retained for the whole length of the extension and a hipped or half-hipped roof should be used.

2. Where a 2 storey extension is proposed to a dwelling which has a pitched roof, the extension should also be constructed with a pitched roof, irrespective of siting, and tiled to match the existing dwelling.

3. Dormers must be in keeping and in scale with the roof area in which they are installed. Separate dormers which reflect the window proportions of the main dwelling are visually more appropriate than a single large dormer. Large box like structures which appear to add an additional floor to the dwelling by completely altering the original roofline will not be permitted. Dormers should not break through, or extend above, the existing ridge line.

4. If dormers are appropriate and otherwise acceptable, their impact on visual amenity and the character and appearance of the area can be minimised by siting them on the elevation of a property least visible in the street scene, usually the rear.

5. The detailed design of an extension should reflect elevational features of the original dwelling such as windows, doors and cornice lines. The horizontal or vertical emphasis of the extension should be in keeping with the property to which it relates visually in the street scene.

6. On south facing rear elevations there may be scope, without prejudicing the visual aesthetics of the design, to seek enlarged glazed areas in order to maximise passive solar gain.

7. Extensions should be constructed in the same materials as specified for the original dwelling in order to avoid visual disharmony and a downgrading effect on the locality as a whole.

8. Where it is not possible or appropriate to use the same materials as the original, a sharp break line should be achieved by setting the extension backwards, or in exceptional circumstances, forwards of the existing building. This is particularly appropriate where the extension is in a prominent position or where the change in materials is likely to be particularly noticeable in the street scene.

9. The design of an extension must consider the value of any trees and any potential adverse effects on them due to development close by. Extensions should not lead to the loss of important trees both during construction works and in the longer term.

10. Any extension to a property which would by reason of its size, siting or design be so overly oppressive or dominating in relation to an adjoining dwelling as to unduly overshadow or cause loss of daylight or sunlight will not be permitted.

11. In some cases the Council will need to test individual proposals against the criteria set out in the Building Research Establishment document, Site Layout Planning for Daylight and Sunlight - A Guide to Good Practice (1991). Applicants will be advised if such investigations identify particular difficulties.

12. Where the principal windows of two dwellings are directly opposite each other, at least 21 metres should be maintained between the windows so as to avoid an unacceptable loss of privacy.

13. In order to avoid an unacceptable loss of privacy to the private garden areas of adjoining properties, all new windows and balconies should have their principal outlook so that it avoids direct overlooking into such areas and none should overlook these areas at a distance of less than 21 metres.

14. Windows which have a flank outlook into the private garden area of an adjoining property will not be permitted. Where such windows are exceptionally justified, the use of high level strip windows or obscured glass, with top opening fanlights only, will be required.

15. The provision of a balcony above a flat roofed extension will not be acceptable unless fitted with a privacy screen to block out flank views into the private area of adjoining properties. Such privacy features must be designed so that they do not harm the character or appearance of the individual dwelling or the wider area.

16. In order to minimise any reduction in daylight into adjoining dwellings, and any impact on the outlook from such dwellings arising from an extension, both single and two storey rear extensions should be designed so as to fall within the relevant 45° angle zone as taken from the nearest habitable room window of an adjoining property (see diagram). Large two-storey rear extensions are unacceptable where dwellings are closely spaced.

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17. Proposals for extensions should minimise loss of sunlight and overshadowing on the private garden area of adjoining dwellings. An extension should therefore be carefully designed in terms of size and siting in relation to adjoining properties, particularly where an extension is set to the south or west of an adjoining property. The private area is normally considered as being an area 3 metres in depth extending from the rear main wall of a property.

18. Parking provision will be required to meet the adopted parking standards for the increased number of bedrooms. Depending on the nature of the road onto which access is being gained, it may be necessary to provide on-site turning and improved visibility splays. Car parking and visibility splays should be designed and located so as not to harm the visual quality of the street scene.

19. The design of an extension to a building in a Conservation Area should respect the special architectural and historic character of the area as required by Local Plan Policy P4/4. This may require traditional designs, proportions, building methods and materials to be used, depending on the individual building concerned and its situation in the street scene.

20. Proposals for extensions to Listed Buildings will be considered under the terms of Policy P4/1.