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Extensions

Single-storey extensions

Rear and side extensions on one level, built to match your house. Designed, approved and built by SK Residential, with a fixed price in writing for the agreed specification.

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What is a single-storey extension?

A single-storey extension adds one level of new floor space to the back or side of a house, usually to open up a kitchen, dining or family room. It is the most common way to gain space without moving, and many can be built without a planning application.

Single-storey rear extension with bifold doors and a roof lantern on a red-brick 1930s semi

We design the extension around how you use the house: where the light comes from, how the new room joins the old one, and what happens to the drains and the garden. The structure is built in brick or block to match the house, finished with a flat roof and lantern or a pitched roof, then insulated, plastered and handed back ready to decorate.

Typical time on site
10 to 16 weeks
Guide price
£2,600 to £4,000 per m²
Building regulations
Required

What is included?

  • Measured survey and design drawings
  • Planning or lawful development certificate where needed
  • Building control application and inspections
  • Foundations, drainage and structural steel
  • Brickwork, roof, glazing and insulation
  • First-fix and second-fix electrics, plastering and making good

How much does a single-storey extension cost?

A 20 m² rear extension at a good specification is typically around £60,000 to £70,000 including VAT.

Single-storey extensionsGuide price incl. VAT
Standard specification£2,600 to £3,000 per m²
Good specification£3,000 to £3,500 per m²
High specification£3,500 to £4,000 per m²

Unit: per m² of new floor area. Guide ranges only; your price is fixed in writing after the survey.

Use the guide price tool for a figure based on your size and specification, or see all guide prices.

Does a single-storey extension need planning permission?

England

In England a single-storey rear extension can often go ahead under permitted development: up to 3 m deep on an attached house or 4 m on a detached one, no higher than 4 m, with eaves no higher than 3 m within 2 m of a boundary. Deeper extensions, up to 6 m or 8 m, need prior approval from the council first. Flats, maisonettes, listed buildings and houses whose permitted development rights have been removed need full planning permission.

Wales

Wales has its own permitted development rules, set by the Welsh Government. Small single-storey rear extensions can often go ahead without an application, but the limits differ from England's and there is no larger-extension prior approval route, so we check the current Welsh rules for your house before drawings are finalised.

Scotland

Scotland has its own householder permitted development rules, and small single-storey rear extensions are often covered. Whatever the planning position, you need a building warrant from the council before any building work starts, and a completion certificate at the end.

Northern Ireland

In Northern Ireland permitted development is set by the Planning (General Permitted Development) Order (Northern Ireland) 2015, and small single-storey rear extensions can often go ahead without an application. Building control approval from the council is still needed.

What about building regulations?

Building regulations approval is always needed: foundations, structure, insulation, drainage, fire escape routes, ventilation and electrics are all inspected.

What should I think about before starting?

  • Drains under the footprint may need diverting or a build-over agreement with the water company.
  • Building on or near a shared boundary usually means serving a party wall notice in England and Wales.
  • Large glazed areas need to meet energy rules, which can shape the size of doors and rooflights.
  • Kitchens and doors have long lead times, so we order them early.

How does the project run?

  1. Tell us about the project. Call, use the guide price tool or send the form with a few photos and a postcode.
  2. Free site visit. We measure up, look at access, drains and the structure, and talk through options and budget.
  3. Design and fixed price. You get drawings and a written price for the agreed specification before anything is ordered.
  4. Build and hand over. Our teams build to the programme, building control inspects, and you get the completion paperwork at the end.

Questions about single-storey extensions

How much does a single-storey extension cost?

Most single-storey extensions cost about £2,600 to £4,000 per square metre including VAT, depending on specification, glazing and ground conditions. We give a fixed price in writing for the agreed specification after the survey.

Do I need planning permission for a single-storey extension?

Often not in England, if the extension stays within permitted development limits: 3 m deep on an attached house or 4 m on a detached house, and no higher than 4 m. Larger ones need prior approval or a planning application. Wales, Scotland and Northern Ireland have their own rules.

How long does a single-storey extension take to build?

The build itself usually takes 10 to 16 weeks once work starts on site. Design, approvals and ordering usually add 6 to 12 weeks before that.

Can we stay in the house during the build?

Usually yes. We keep the existing house closed off from the works until the knock-through near the end, and agree a temporary kitchen set-up with you if the kitchen is affected.

Do you need to dig up the drains?

Sometimes. If a public sewer runs under the extension, the water company has to agree a build-over or a diversion. We check this at survey stage.

Will the brick match?

We source the closest available match for colour, size and texture and agree a sample panel with you before laying.

Related projects

Guides

Where do we build single-storey extensions?

We take on single-storey extensions across England, Wales, mainland Scotland and Northern Ireland. Choose your area:

Planning an extension, loft or new home?

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