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Design Guide to Domestic Extensions
External Design and Appearance
The careful consideration of the external appearance of
an extension must not be ignored if a sympathetic addition to your dwelling
is to be achieved. It is usually easier and more successful to copy the
appearance of the existing house, however, a contrasting design using
different materials can achieve satisfactory results when the effect is
to change the overall appearance of the dwelling.
Physical Constraints
The most obvious constraint to any extension is the amount
of physical space available for the extension, the location to the existing
house and its relationship to the nearest boundary. The obvious functional
aspects such as structural stability and general construction standards
are covered by the application for Building Control approval. An extension
may affect car-parking arrangements by restricting vehicle manoeuvring
space or the need to form a new access. An extension can also affect the
neighbouring house and gardens in terms of potential loss of sunlight,
daylight and privacy. A window in the side of an extension for example
or even a new window on an existing wall can cause problems of overlooking,
that may be rejected by the local Planning Office.
Form and location of side and rear extensions
The extension must not dominate the appearance of the
existing house, its shape, size and position must be carefully considered,
if a harmonising between old and new is to be achieved. Great care must
be taken in the selection of external materials, which should normally
match those already found on the existing house. The aim will be to integrate
the extension with the original house keeping the number of materials
used to a minimum. In the case of many older houses the existing materials
will have changed colour and texture due to age and weathering and may
require cleaning to restore their appearance. The reuse of existing materials
such as roofing tiles can greatly improve the integration of the extension
into the existing house. In general the following factors could be said
to contribute to a well-designed extension.
(a) A new extension harmonises with the original appearance of the house.
(b) It has a pitched roof compatible with the existing roof.
(c) The colour and shape of roof materials and ridge tiles match existing.
(d) Eaves line up with those of the main house.
(e) The type and proportions of new windows echo those in the original house.
(f) New windows positioned to conform to the existing symmetry.
(g) Materials and detailing match those already found on the house.
The following factors could be said to contribute to an unsightly extension.
(a) The extension ignores the style, character and appearance of the original house.
(b) It has a flat roof that clashes with the existing pitch roof and gable.
(c) There is a clumsy junction between the old and the new roofs.
(d) It has inappropriate windows that differ in shape, in alignment, and materials from the existing.
(e) The new materials for walls and roofs of the extension are unattractive and incompatible with the existing house.
Roofs
To achieve the aim of harmonising an extension
to an existing house, the new roof must match the style, pitch, colour,
material and shape of the existing. The line of the eaves of two storey
side and rear extensions must also line up with those of the existing
house. The colour and shape of new tiles and slates should match those
of the existing roof, this is particularly important when the new roof
connects directly into the existing.
Windows and Doors
The style, shape and detailing of windows
and doors to the extension must correspond with the appearance of their
counterparts in the existing house, if a satisfactory integration of
design is to be achieved. The proportional size, sill and lintel heights
of new window openings should conform in general terms, echoing those
of the main house. The symmetry of window and door positions should
be maintained to preserve the character of the existing house.
Dormer Windows
It is rarely desirable to add dormers to the
front of the house, but where necessary they must have a pitched roof
and materials to both the roof and the sides of dormer windows should
match those existing on the roof. Try to ensure that the dormers relate
to the shape, position, design and size of the existing doors and windows
and ensure that the construction of dormer windows and other roof extensions
do not dominate the original house. This will require any new dormer
to have a clear area of roof around its perimeter and to be kept as
small as possible.
Services
The location of services to the existing house
must be investigated and established so that the extent of any alteration
to them can be realised. This is particularly true for rainwater down
pipes, soil vent pipes and underground drainage runs. It is preferable
that pipe-work or wiring for gas. T.V., etc. should be run up rear elevations
wherever this is practical.
Home improvements can cost a lot of money so how can you borrow? We examine a few of the options.
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