Planning:

Residential extensions / alterations

INTRODUCTION

People often need to extend their homes as an alter-native to relocating to another property, but it is important that extensions are appropriate in design, size and appearance to the original building. Extensions can have a significant impact upon the appearance and character of a building, and larger extensions can often be inappropriate. It is worth remembering that bad design can also reduce the value of your home and also affect the surrounding area.

This guide is intended to provide advice about designing extensions in the Borough of Berwick-upon-Tweed. It should help to ensure that your extension makes a positive contribution to your house and the surrounding area in a way that does not adversely affect your neighbours, especially where your house is within a town or village.

Before considering an extension, please read these notes carefully Applications for planning permission will be considered against the principles shown within this guide.
GENERAL DESIGN PRINCIPLES
Your existing house was designed as a whole, and the Council will expect alterations and extensions to reflect its present character and appearance in a manner that will enhance rather than detract from the building.

Ideally, any extension should appear as though it were an integral part of the original design.

An extension should not dominate the existing building by being overlarge. It should harmonise with the shape, roof pitch and proportions of the original building.

The design of an extension to a Listed Building or a building in a Conservation Area should be treated with particular sensitivity so as to preserve and enhance the appearance of the building and its setting.

Roofs should normally be pitched, and at an angle that equates as closely as possible to that of the original building (This may determine the appropriate width for an extension), and should rise no higher than any part of the existing roof ridge of the house.
Flat roofed extensions, although very often the least expensive option in terms of initial outlay, can often give rise to considerable maintenance costs later, and they very rarely look right. Such extensions are not encouraged, and will not be granted permission where they are visible from a public area.

SIDE EXTENSIONS
Extensions will often have a big impact upon the appearance of the house and the street. They should relate well to the front of the existing house, following through the original style, proportions and features. Windows are often the most dominant features of the building, and therefore, it is important that window styles and openings in existing buildings are repeated in the extension.

Most houses have openings with a vertical emphasis (i.e. windows are positioned directly above one another, rather than randomly across the same elevation, and are taller than they are broad), and where this is the case, this emphasis should be replicated in the extension.

In general, extensions should be subservient to the main building. With side extensions, this can be achieved by setting the extension back from the front wall, and keeping the maximum height to below the existing roof ridge.

If you live in a street where your house is very similar to those of your neighbours, it will rarely be acceptable to extend your house in a manner that would make it stand out.

If your house forms part of a street where most of the buildings are detached or semi-detached, it is desirable to retain gaps or open spaces between buildings so that “terracing” does not occur. In order that this can be achieved, it is recommended that there is a clear gap of one metre between the flank wall of your property and your boundary. It may also be desirable to set the front wall of the extension back, so that the perception of a gap is maintained.
REAR EXTENSIONS
A rear extension is very often the only way of providing additional space. However, it is also very often the type of extension that is most likely to affect your neighbours. So that the effect upon the neighbouring properties is kept to a minimum, single storey extensions abutting a common boundary should not exceed three metres in length, unless there is an existing extension to the rear of the adjoining property. This should help prevent your extension from dominating your neighbour’s house or garden or affecting light. The Building Research Establishment daylight and sunlight indicators (1991) will be used to assess the effect of any extension on light to a neighbouring property, where necessary.

Two storey extensions on common boundaries are unlikely to be acceptable, and where they are proposed, they should be sited as far as practicable from common boundaries.
In order to prevent overlooking neighbouring properties, avoid windows in side walls of rear extensions, particularly at first floor level, unless they can be obscure glazed, and you don’t mind them being fixed shut.

In the case of two storey rear extensions, try to keep the eaves level as low as possible, by providing the first floor accommodation within the roof-space of the extension, so as to keep the overall height of the extension as low as possible.

You should also consider your own amenity. Your proposals might mean that existing rooms become darker or less attractive, and if it is to be built against an existing boundary, how will it be maintained?

Your extension should not take away your ability to park your car off the street if this kind of provision already exists.

Roof terraces over single storey rear extensions are quite common but may cause too much overlooking of neighbouring properties. They are unlikely to be acceptable within a terrace or some semi-detached properties.

FRONT EXTENSIONS
With the general exception of porches, extensions to the front of properties, particularly those occupying prominent positions, will seldom be appropriate.

Like other extensions, porches should harmonise with the existing house. They should not normally extend more than a metre and a half beyond the front of your house, and should have a pitched roof that does not extend higher than the bottom of first floor windows.

ALTERATIONS TO THE ROOF
Another means of providing additional accommodation is to create accommodation within the existing roofspace.

The size and number of dormer windows should be kept to a minimum, and should be of traditional design. They should be kept below the ridge line of the main roof, and should have a pitched roof at the same angle as the main roof.

Unless there are similar traditional examples characterising the surrounding houses, it is better to avoid dormers on front-facing roofs, particularly in Conservation Areas.
Flat roofed dormers or those that dominate or obscure the original roof will not be permitted. Dormers should normally be set at least one metre in from the side of the house (which will help prevent the appearance of an additional storey, particularly from the side), and should generally be vertically in line with the windows below them.

In keeping with traditional window styles, dormers should normally be taller than they are wide.

CONSERVATORIES AND GARAGES
An appropriate conservatory should generally meet the criteria relating to other forms of extension. They should harmonise with the existing house, and should not be allowed to dominate the elevation on which they are to be constructed. Conservatories should adopt the simplest possible form, and so lean-to types are very often the most appropriate. On older properties, UPVC conservatories are not encouraged, with timber and glass construction being more appropriate. The materials used in the base of the conservatory will normally be expected to match those of the main body of the house. UPVC structures are not acceptable on listed buildings or on many buildings in Conservation Areas.

New garages should also relate well to the existing house, and should follow the principles relating to other extensions. Detached garages will normally be expected to have a pitched roof, which will not only look better, but will also provide additional storage space. Doors should preferably be of timber construction, but in any case, should have a vertical boarding pattern. A hinged side-hung rather than up-and-over door opening mechanism will normally be preferred.

MATERIALS
The Council will normally expect the external materials used to construct an extension to match as closely as possible those of the existing house. Different materials normally detract from the overall appearance of the finished building.

Reclaimed local stone or matching brick may be suitable for older buildings, but where a good match is difficult, the appearance may be less jarring if the wall of the extension is set back.

Slates and tiles should match the main roof, and again, you may find that second-hand materials are worth considering, particularly on prominent roofslopes, although new materials may soon weather to match the existing.

Unless your house is already rendered, it is inadvisable to render your extension, or to render your whole house so as to match the extension. Where render is proposed, it should match both the existing colour and texture. Smooth render is generally preferred, particularly in Conservation Areas.

Although perhaps not immediately apparent, the use of differing mortars can have a considerable effect upon the integration of the extension to the main body of the house. It is therefore always important to ensure that a matching mortar is prepared.

Decorative detail or features, such as corbelling, string courses and window surrounds, should be carried through from the original house.

Types of window have varied through time, although generally, the traditional window type throughout the
Borough is the timber sliding sash. This type of window will normally be the only appropriate form for older properties within the Borough, particularly if they are Listed or in a Conservation Area, and especially if they are within public view.

In many cases, even newer properties have timber sliding sash windows, and these will be the preferred type of window on front elevations.

However, whatever style of window your house originally contained, it is usually most appropriate to replicate these in your extension, so that the character of your house is carried into the extension. Where windows are set back in a reveal, this detail should be matched in the extension.
Original openings should not be widened, and unless characteristic of your existing house, windows should not be wider than they are tall. They should also follow the vertical emphasis in the manner described in the section pertaining to dormers.

PERMITTED DEVELOPMENT
Certain extensions can be built without the need for formal planning permission, although additional restrictions apply in some parts of the Borough and on Listed Buildings. The Planning Unit will be able to advise on whether permission is required for your extension or alteration. However, even where permission is not necessary, the advice contained within this leaflet will still apply to ensure the most appropriate design and impact.