Rear extension

The short answer

A rear extension adds space to the back of a house, most commonly to enlarge a kitchen or create an open-plan living and dining area. Depth and height limits under permitted development vary by council and property type, and many rear extensions still need planning permission, particularly in conservation areas or where a previous extension already exists. Costs depend on size, glazing and roof design, with flat and pitched roof options costing differently.

What the project involves

Typically a single-storey addition with a flat, pitched or lantern roof design, often incorporating large glazed doors onto the garden and sometimes a structural opening into the existing kitchen or living room.

Consents and regulations in Scotland

Rear extensions often qualify for permitted development up to certain depth and height limits set by the relevant council, but conservation areas, listed buildings and flats generally have reduced or no permitted development rights. A building warrant is required regardless of planning status.

Sequencing

Design, planning check, building warrant, foundations, structure and roof, glazing installation, then services and internal finishing, often combined with a kitchen renovation.

What commonly goes wrong

Underestimating how much a flat roof lantern design costs compared with a simple flat roof, drainage falls not being planned around the new footprint, and disruption to existing kitchen use during the connecting structural opening works.

What it usually costs

Indicative ranges only, to help you judge a quote. They are not an estimate for your property — only the business doing the work can give you that.

• Basic flat-roof rear extension: the lower-cost option for a straightforward footprint.
• Roof lanterns or full-glazed gable ends: add notable cost but bring more natural light.
• Structural opening into the existing house: adds a steel beam and building warrant cost on top of the extension itself.
• Drainage rerouting: can add cost where the new footprint sits over an existing drain run.

What to do, in order

1. 1Check depth and height limits for permitted development with the relevant council.
2. 2Finalise design, including any structural opening into the existing house.
3. 3Obtain planning permission if required, and a building warrant in all cases.
4. 4Complete foundations, structure and roof before internal works.
5. 5Fit glazing and complete the structural opening into the existing house.
6. 6Finish internally and arrange final inspection.

Local detail for the Lothians

• In Edinburgh's tenements, ground-floor rear extensions into a shared back green need the consent of other owners with rights over that ground, in addition to planning permission.
• Conservation area properties in the New Town and other historic parts of Edinburgh often have reduced permitted development rights, making a formal planning application more likely to be needed.
• Mid Lothian and East Lothian villages with conservation area status can have similar restrictions on visible rear extensions where they affect a shared streetscape.
• In West Lothian's more recently built housing, rear gardens are often smaller, which can limit how large a rear extension can be relative to remaining garden space under planning policy.

When you need a professional

An architect can advise on permitted development limits and design a rear extension that suits the existing house, with a structural engineer designing any opening into the current kitchen or living space.

Common questions

How far can I extend at the rear without planning permission?

This depends on the property type and council policy, with different limits for detached, semi-detached, terraced houses and flats, so checking with the council before designing is worthwhile.

Can flats get a rear extension?

Ground-floor flats sometimes can, subject to planning permission and the consent of other owners with rights over the shared ground.

Related pages

• House extension

  Adding floor space to a house, from a single-storey side extension to a two-storey addition.

• Kitchen renovation

  Replanning layout, units, worktops and services in the room most homes are refitted around.

• Conservatory or garden room

  Adding a lightweight glazed room or a fully insulated garden building for year-round use.