I Want to Extend My House

Your home may have already been extended over time, or it may have been built in one go. When deciding on an extension it’s important to understand how the house has changed in the past, its particular character and how it sits within the garden or surroundings - its ‘setting’.

Planning permission and building regulations approval may be required to extend your house. In addition, you will need listed building consent if your building is listed. You should seek advice on the need for consent before carrying out these changes.

What should my extension look like?

If your property has previously been altered or extended, permission for a new extension may be possible, so long as it does not overpower what is already there. It may be possible to replace a poorly built and designed extension with a new structure.

A new extension should not dominate a historic building: this usually means it should be lower and smaller. Some small buildings such as lodges and cottages can easily be swamped by an extension, unless very carefully designed. There is no rule on the ideal percentage increase in size: it all depends on the size, character and setting of your house. There will still be some cases where a new extension will not be possible.

An extension will usually have less effect on your historic house if it is built onto the back and not seen from the front. This is because the back is usually less important for its architecture than the front. Side extensions may also work well. Permission for an extension that projects to the front is rarely given as this is usually the most important and most visible part of the house.

Connecting doorways

When you build an extension, you will need to connect it to a room in the existing house. You may be able to avoid removing any historic walling if there is an existing doorway, but sometimes a new opening will be needed. The decision about where to make the new doorway needs careful thought. In some houses, such as medieval timber-framed buildings, removing part of a wall to form a doorway can cause structural problems.

A new doorway may also spoil the design of a panelled or significantly decorated room. Once old fabric is removed it is lost forever. You also need to think about how the extension will affect windows and daylight in existing rooms. It may be worth keeping old windows where they are, as features.

Choosing the right materials

The exterior needs to be carefully designed. You should expect to use matching or complementary materials for walls and roof. However, cleverly chosen contrasting materials in a modern design may work well for some buildings, where the extension can then be clearly ‘read’ as different to the old house. But the effect should not be so different that the extension is more prominent than the main building.

Windows on an extension are likely to need double-glazing to comply with the Building Regulations that apply to new construction, though there may be some exceptions. It is important to choose sympathetic styles for any new doors or windows. The physical detail of the junction between old and new is important, to avoid water getting into the old house, and to disturb the historic wall as little as possible.

As there are important design matters to get right, using an architect or surveyor with experience of extending historic buildings will help. See Finding Professional Help.