Rear, side, wrap-around or front: the main types of house extension

Single-storey rear extensions

The most common type. It pushes the back of the house into the garden, usually to create an open-plan kitchen-diner. Many fall within permitted development within set depth and height limits, though prior approval or planning permission may be needed for larger schemes.

The main design decisions are roof type (flat with a lantern, or pitched), how the new space joins the existing house — often via a steel beam — and glazing onto the garden.

Side and side-return extensions

A side extension fills space beside the house. On Victorian and Edwardian terraces, the narrow passage beside the rear wing is called the side return; infilling it widens a cramped kitchen dramatically.

Side extensions bring boundaries into play: drainage along the side, party wall matters and neighbours' light. Access for materials can become difficult once the side is built on, so sequencing matters.

• Boundary position and party wall notices
• Drains often run along the side of the house
• Neighbour light and outlook
• Keeping access to the rear during the build

Wrap-around and L-shaped extensions

A wrap-around combines rear and side extensions into an L shape around the corner of the house. It creates the largest ground-floor space and is often the solution for a period terrace or semi where the rear wing leaves an awkward courtyard.

Because it is larger and usually exceeds permitted development, planning permission is normally needed. The roof junction where the two arms meet needs careful detailing to avoid leaks.

Double-storey extensions

Going up two floors adds bedrooms as well as living space, for proportionately less foundation and roof. Double-storey side extensions are common on detached and semi-detached houses. They almost always need planning permission and are judged on their impact on the street and neighbours.

Where there is already an attached garage, building over it is a related option — see our separate guide on over-garage extensions.

Front extensions and porches

Front extensions are the most tightly controlled because they change the street scene. Small porches can be permitted development within limits; anything larger generally needs permission. They suit houses with a deep front garden and a cramped hallway.

A note on construction method

Most extensions we build are blockwork with rendered or timber-clad finishes, but timber-frame construction is another route. The type of extension (where it goes) and the construction method (how it is built) are separate choices. Your designer or engineer will advise on the method for your site.

Choosing between them

Start with what the new space must do, then look at plot, boundaries, drainage and planning constraints. A free site visit is the quickest way to rule options in or out. Anthony walks the property, looks at access and ground, and talks through which types are realistic before any drawings are commissioned.

Common questions