A single-storey extension in Nottinghamshire typically costs between £1,800 and £2,600 per square metre at a standard specification, which works out at roughly £30,000 to £55,000 for a family-sized rear extension. The exact figure depends on the size, the finish you choose, and how much structural work is involved. Want a number based on your own project rather than a national average? Try our instant extension estimator and get a ballpark figure in under a minute.

Why per-square-metre pricing is the easiest way to think about it

Builders price extensions per square metre because it’s the fastest way to compare like with like. Foundations, roofing, walls, windows, electrics, plumbing and plastering all scale roughly with the size of the space, so multiplying your floor area by a price-per-m² figure gives you a sensible starting point before you get a proper quote.

In Nottinghamshire, that figure usually sits between £1,800 and £2,600 per square metre for a full-build extension finished to plaster. Basic specifications with simple windows and standard bricks sit nearer the bottom of that range. Extensions with bifold doors, roof lanterns, underfloor heating or a full kitchen fit-out push towards the top, and sometimes above it.

What a single-storey extension actually costs

To put that into real numbers:

  • A 12m² extension (roughly the size of a small kitchen extension) typically costs around £22,000 to £32,000 including VAT.
  • A 20m² extension (a common size for an open-plan kitchen-diner) usually comes in at £40,000 to £55,000.
  • A 30m² extension (a larger family space, sometimes wrapping around the side of the house) tends to land between £55,000 and £80,000.

These are ballpark figures, not fixed prices. Every extension is different once you factor in ground conditions, access for materials, and how much of your existing house needs opening up to connect the new space.

Want to see where your own project sits? Head to the instant extension estimator, pick your extension type, set your dimensions, and you’ll see a live price range update as you go.

What actually pushes the price up or down

A handful of things make the biggest difference to your final figure:

Glazing. Bifold or sliding doors and roof lanterns are the fastest way to add £5,000 to £15,000 to a project. They also transform how a space feels, so it’s often money well spent, but it’s worth knowing upfront.

Kitchens and bathrooms. The fit-out (units, worktops, tiling, appliances) often costs as much as people expect the whole extension to cost. It’s a separate budget line from the building work itself.

Structural openings. If you’re knocking through into the existing house with a large steel beam, that typically adds £2,000 to £6,000 depending on the span.

Ground conditions and drains. Clay soil, nearby trees, or drains that need diverting or building over can all add cost and time. If your extension goes over a drain, you’ll need a build-over agreement with Severn Trent, which your builder should sort out for you.

Spec choices. Matching brick versus render or cladding, standard windows versus aluminium, basic flooring versus underfloor heating. These choices, more than anything else, explain the gap between £1,800/m² and £2,600/m².

Do you need planning permission?

Most single-storey rear extensions in Nottinghamshire fall under permitted development, which means you can build without a full planning application, provided you stay within the rules. As a rough guide:

  • Up to 3 metres beyond the rear wall for an attached house (semi-detached or terraced).
  • Up to 4 metres for a detached house.
  • Under the larger home extension scheme, this can extend to 6 or 8 metres with prior approval from the council.

Conservation areas, listed buildings, and homes that have already used up their permitted development allowance usually need full planning permission instead. It’s always worth checking with your local authority before you commit to a design, since the rules can catch people out.

How long does it take?

Most single-storey extensions in Nottinghamshire take 10 to 16 weeks on site from breaking ground to a finished, plastered space, though this depends on the weather, how easy the site is to access, and how much of the existing house needs altering to connect it.

Why a ballpark figure is only the starting point

A price-per-square-metre range is useful for early planning, but it can’t account for your specific house, your ground conditions, or the finish you actually want. Two extensions of exactly the same size can cost very differently depending on what’s underneath the ground and what’s going into the build above it.

That’s exactly why we built the instant estimator. It gives you a realistic range in a couple of minutes based on your extension type, dimensions and any upgrades you’re considering, so you walk into a conversation with us already knowing roughly what you’re working with. From there, if you want a proper, accurate quote, you can submit your details (and your drawings, if you have them) directly through the tool and we’ll follow up.

Try it for yourself

If you’re at the early stages of planning an extension in Nottinghamshire, South Yorkshire or Derbyshire, the quickest way to get a feel for cost is to try it yourself.

Try the Instant Extension Estimator

Set your extension type and size, see the price range update live, and get in touch when you’re ready for an accurate quote from Rosebrick Developments.