Modular Extension Cost
A factory-built, single-storey extension costs £2,100 to £3,300 a square metre in 2026, finished and craned in. Pick a size.
Choose a size to see the price.
Finished and craned in, VAT included. With drawings, engineer and building control: . A national guide, not a quote.
- £2,100 to £3,300a square metre, finished and craned in, VAT included
- +20 to 40%in London and the South East
- £1,400or so for a day of crane and lifting crew, already in the rate
- £548council fee in England if you need planning permission
Modular extension cost calculator
Set the floor area, then the things that move a budget most. The first line covers the finished room, a standard base, delivery and a one-day lift.
About 4 m by 5 m.
Budget for the whole job, VAT included
Where these figures come from
Typical national ranges for 2026, VAT included. Expect 20 to 40% more in London and the South East. A guide, not a quote. The rate per square metre, the crane day, the fit-out lines and the professional fees are typical ranges from UK cost guides published during 2026, shown as a whole range rather than a midpoint. Building control fees are set by each council. The planning fee is the one set nationally for England from 1 April 2026.
What the price covers
The per-metre figure buys a finished room: frame, insulation, roof, windows and doors, wiring, plaster, a standard base, the lorry and the crane.
It stops where houses start to differ. Kitchen units, piles on clay, a moved drain and the fees for drawings all sit outside it.
Typical prices by floor area
Single storey, clear crane access, outside London and the South East, VAT included.
| Floor area | The room | With fees |
|---|---|---|
| 12 m² | £25,000 to £39,500 | £27,500 to £44,500 |
| 16 m² | £33,500 to £53,000 | £36,000 to £58,000 |
| 20 m² | £42,000 to £66,000 | £44,500 to £71,000 |
| 25 m² | £52,500 to £82,500 | £55,000 to £87,500 |
| 30 m² | £63,000 to £99,000 | £65,500 to £104,000 |
| 40 m² | £84,000 to £132,000 | £86,500 to £137,000 |
A brick and block build of the same room costs about £2,200 to £3,200 per m², so modular against traditional is a choice about time more than money. More sizes on the cost by size page.
Quick answers
How much does a modular extension cost in the UK?
£2,100 to £3,300 for each square metre of floor in 2026, finished, craned in and with VAT included. A 20 m² room comes to £42,000 to £66,000.
Is modular cheaper than building in brick?
Not by much, and sometimes not at all. A traditional single-storey build runs about £2,200 to £3,200 per m². The saving is time: the room is made in a factory while the base goes in, then lifted on in a day.
Why is the range so wide?
Glass, ground and finish. A wall of sliding doors, clay soil near trees or a high-end fit-out each push a price towards the top.
Are prices the same everywhere?
These are national figures. London and the South East usually cost 20 to 40% more, and the calculator has a setting for that.
Get a quote for your extension
A guide figure only goes so far. Tell us where the house is and what you want built, and a builder can price the real thing.
Your pick:
This site is a free introduction service, not a builder. We look for a firm that builds modular extensions where you live and tell you its name. Your details go to that firm only once you say yes.
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- We look for a builder that makes this kind of extension and works in your postcode, then ring or email you with its name.
- Nothing is passed on unless you tell us to go ahead.
- The builder visits, looks at the ground and the street, and gives you a price in writing. We never send marketing.