Ground Floor Extension Options

Rear extensions

A rear extension pushes the back wall into the garden. It is the most common ground floor extension because it is simple to build and usually creates the open kitchen-diner people want. The main limits are depth, because of neighbours' light, and height near the boundary.

Under permitted development a single-storey rear extension has depth and height limits that depend on whether the house is detached, and larger depths can sometimes be approved through the prior approval route. The planning guides on this site explain the process; beyond those limits, a householder application is needed.

Side return extensions

Many Victorian and Edwardian terraces have a narrow side passage beside the back addition. Filling it with a side return extension widens the kitchen, often only by a couple of metres, but that is enough to turn a galley kitchen into a room with an island or dining table.

Light is the challenge, because the side return removes a window from the original kitchen. A glazed roof or large rooflights over the new section usually solve it, and they are part of what makes this style popular.

Wrap-around extensions

A wrap-around combines a side return and a rear extension in an L shape. It gives the most floor area and allows a clear split between cooking, dining and living. It is also the most involved option: it usually needs planning permission, more structural steel where the old walls come out, and careful design where the two roofs meet.

The separate guide on L-shaped extensions looks at wrap-around design in more detail, including roof junctions and drainage.

Comparing the three shapes

The table sets out the typical fit for each option; the final choice always depends on the individual house and garden.

Ground floor extension shapes compared. Shape | Best suited to | Main watch-points. Rear — Most houses with a usable garden — Depth and height near boundaries, drainage runs; Side return — Terraces and semis with a side passage — Light to the middle of the plan, party wall work; Wrap-around — Owners wanting the maximum ground floor space — Planning, roof junctions, structural steel

Things that shape every ground floor extension

Whatever the layout, a few practical factors decide cost and programme more than the shape itself.

Drains: a manhole or sewer under the footprint may need diverting or a build-over agreement · Ground conditions and trees, which set the foundation depth · Party wall notices where the extension is on or near a shared boundary · Steel beams where existing walls are opened up · Glazing: bi-folds, sliders and rooflights, which affect both light and heat · Building regulations sign-off for structure, insulation, drainage and fire safety

Where to go next

Once the shape is chosen, the useful next steps are budgeting and planning. The single-storey extension cost guide and the extension cost per square metre guide cover money; the permitted development guide covers what can be built without an application; and the single-storey extension stages guide explains what happens on site, week by week.

Frequently asked questions

What is a ground floor extension?

Any single-storey addition to the ground floor of a house, most commonly a rear extension, a side return or a wrap-around combining the two.

Do ground floor extensions need planning permission?

Many rear extensions fall within permitted development if they stay within the depth and height limits. Side returns on some houses and most wrap-arounds need a planning application.

Which ground floor extension adds the most space?

A wrap-around, because it extends both to the side and the rear. It is also the most complex to design and build.

How do you keep a side return extension light?

With a glazed roof or large rooflights over the new section, since the extension removes the original side window.