Modular house extension cost
A craned-in extension typically costs £2,100 to £3,300 a square metre, including VAT. Set the room, the size and how the crane gets in, and the calculator gives a range for the whole job.
Guide price, including VAT
£50,500 to £69,500
£42,000 to £58,000 before VAT at 20%
A guide, not a quote. National figures for the finished room on a standard base with a one-day lift. Design and council fees, and kitchen units, are extra. London and the South East usually cost 20 to 40% more.
The cost of a modular extension by size
These are for a house with clear crane access outside London and the South East, including VAT at 20%. They cover the finished room, a standard base, delivery and a one-day lift.
They are national figures: a guide, not a quote. A firm can only fix a price after seeing the ground and the street.
| Floor area | Living room or bedroom | Kitchen or kitchen-diner |
|---|---|---|
| 10 m² | £21,000 to £29,000 | £25,000 to £33,000 |
| 15 m² | £31,500 to £43,500 | £37,500 to £49,500 |
| 20 m² | £42,000 to £58,000 | £50,000 to £66,000 |
| 25 m² | £52,500 to £72,500 | £62,500 to £82,500 |
| 30 m² | £63,000 to £87,000 | £75,000 to £99,000 |
| 40 m² | £84,000 to £116,000 | £100,000 to £132,000 |
| 50 m² | £105,000 to £145,000 | £125,000 to £165,000 |
What sits outside that figure
None of these is unusual, and together they can add a fifth to the bill. Ask each firm which it has included, so that you compare like with like.
Where the figures on this page come from
Rates per square metre, crane hire and the extra for difficult access are typical national ranges for 2026, including VAT. How the range is divided between room types is our own judgement, and the module sizes in the calculator are a working assumption of 3.5 m by 8.5 m at most; makers differ. Professional fees are typical national ranges; the party wall figure assumes one surveyor agreed by both sides, and if your neighbour appoints their own you pay for both. Planning fees are set by MHCLG from 1 April 2026.
| Item | Typical cost |
|---|---|
| Planning drawings and design | £1,000 to £2,500 |
| Engineer's calculations | £600 to £1,200 |
| Building control fees | £700 to £1,100 |
| Party wall surveyor (each neighbour, one agreed surveyor) | £700 to £1,500 |
| Planning application, if needed England, 2026 | £548 |
| Lawful development certificate Optional proof that no application was needed | £274 |
| Lift over the house, or a road closure | £1,500 to £3,000 |
| London and the South East | 20 to 40% more |
| VAT | 20% |
Where the money goes
Roughly speaking, a modular extension has three bills folded into one. The first is the room: frame, insulation, windows, wiring, plaster, roof. The second is the ground it stands on: excavation, concrete or piles, drains. The third is getting it there and joining it up: transport, the crane, the opening in your wall and the connections.
Only the first is made cheaper by a factory. The other two happen at your house, in the weather, and they are where prices drift. A quote that is vague about foundations or says "connection by others" has left the uncertain part with you.
What pushes a price to the top of the range
Glass. A wall of sliding doors and a large rooflight can cost as much as the walls they replace several times over.
Ground. Clay, made-up ground, or trees within a few metres mean deeper foundations or piles. A trial hole dug before the order is placed costs little and removes the largest unknown. Piles are designed and priced by your engineer after a ground investigation, and can add several thousand pounds.
Access. When the crane must stand in the road and reach over the roof, the machine is bigger and the council is involved. Use the access setting in the calculator to see the difference, and read how delivery works before assuming the worst.
Drains. A public sewer under the new room needs the water company's consent, and sometimes a manhole has to be moved.
Splitting the room. Two modules mean two lorries, a longer day for the crane and a joint to finish indoors.
Comparing two quotes fairly
Put them side by side and mark, for each, whether it includes: foundations to a stated depth, drainage, the structural opening and steel beam, making good inside the house, electrics tested and certified, building control fees, the crane, any road closure, and VAT. Then compare what is left.
Ask each firm how long its price holds and what would change it. A fixed price that depends only on the ground survey is worth more than a lower one with a list of provisional sums.
Cost questions
What does a modular house extension cost per square metre?
Typical national prices in 2026 are £2,100 to £3,300 for each square metre of a ground-floor room, VAT included, with a standard base and a one-day crane lift in the price. Plain rooms sit towards the lower end; kitchens and small pods towards the upper end.
Does modular work out cheaper than brick and block?
Not usually. A single-storey brick and block extension typically costs £1,800 to £3,000 per m², much the same as modular. The base, drains, glazing and finishes are priced alike whichever way the walls go up, and the saving on site labour is spent on transport and the crane. People choose modular for a shorter, more predictable build, not a lower bill.
What is not included in a typical quote?
Design and engineering fees, council fees, kitchen units and appliances, and anything the survey finds in the ground, such as the need for piles, which your engineer prices after a ground investigation and which can add several thousand pounds. Check whether each quote includes VAT. Allow £2,300 to £4,800 for drawings, an engineer and building control together.
How much deposit should I pay?
Factory-built work is paid for earlier than site-built work, because most of the cost is spent before anything reaches your house. Staged payments tied to events you can check, such as drawings approved, module complete at the factory and module delivered, are normal. Be wary of a large payment with nothing to show for it, and ask whether deposits are protected by insurance or held in a separate account.
Does the price include the crane?
Most quotes include a one-day lift where a crane can stand on your drive or beside the plot. Lifting over the house or closing the road is priced as an extra, commonly £1,500 to £3,000 before council fees. A crane on its own costs £400 to £1,500 a day depending on size, and a one-day contract lift with a 25 tonne crane and its lifting crew is about £1,400. See delivery and cranes.
Why do small extensions cost more per square metre?
Because some costs do not shrink with the room. The lorry, the crane, the opening into the house, the building control fee and the electrician’s visit cost about the same for 10 m² as for 30 m².
- Delivery and cranesWhat your street adds to the job
- Modular kitchen extensionsFit-out, drains and glazing limits
- House extension podsSingle small modules
- Modular loft conversionsWhy roof-level work is priced per job
Get a quote for your size
Three short steps, about a minute. Start with the postcode so we know which firms can reach you.
This is a free introduction service, not a modular extension firm. We look for a firm that builds this type of extension where you live and tell you its name. Your details go to that firm only when you say yes.
Thank you. That is everything we need.
- We look for a firm that builds and cranes in this kind of extension in your area, usually within a working day.
- We email or phone you with the firm's name. Nothing has been passed to them at that point.
- If you are happy, we send your enquiry on and they arrange to see the house and the access. We never send marketing.