Modular extension vs traditional
The headline prices are almost the same. The useful question is not which is cheaper, but which kind of money you would rather spend: factory time and a crane, or weeks of trades in your garden.
One room, priced both ways
A 20 m² single-storey kitchen extension. Typical national ranges for 2026, VAT included. Expect 20 to 40% more in London and the South East. A guide, not a quote.
| Line | Modular | Brick and block |
|---|---|---|
| The room, finished Modular includes delivery and a one-day lift | £42,000 to £66,000 | £44,000 to £64,000 |
| Drawings, engineer, building control | £2,300 to £4,800 | £2,300 to £4,800 |
| Kitchen | £15,000 to £35,000 | £15,000 to £35,000 |
| Total before contingency | £59,300 to £105,800 | £61,300 to £103,800 |
The totals overlap almost completely. Where your quote lands inside each band depends on glass, ground and finish far more than on the method.
Where the money goes differently
When you pay
A brick extension is paid in stages as it rises: footings, walls, roof, first fix. A modular maker usually asks for a larger share before the factory starts, because it is buying materials and booking a production slot for a room that only fits your house. Ask how that deposit is protected, and pay the balance against delivery and sign-off rather than in advance.
What the crane replaces
The modular price carries a lift of about £1,400 that a brick build never pays. In return it drops weeks of scaffold, skips, mixers and wet trades. On a tight terrace with no crane access, that trade turns against modular quickly; on a house with a drive, it rarely matters.
The cost of time
No guide puts a figure on living without a kitchen, but you can. If you would otherwise rent somewhere, eat out or take time off to let trades in, count each week. That is the line where modular tends to win, and it is yours to fill in.
Changing your mind
Moving a window on a brick build halfway through costs a day of a bricklayer. On a module that is already made, it may not be possible at all. Decide everything before the factory starts, and treat late changes as the expensive kind.
Which is better value for you
Modular tends to make sense for a rectangular room of 15 m² or more, on a house with a drive or a quiet road behind it, where the family is living at home through the work and wants a fixed price early.
Brick and block tends to make sense for small rooms, awkward shapes, wraparounds and side returns, houses with no room for a crane, and owners who want to keep design decisions open as the build goes on.
Planning and building regulations treat both the same. Neither route changes the £548 householder fee in England, or the need for a building warrant in Scotland.
To see your own numbers, try the calculator with your size and region.
Where these figures come from
Both per-m² bands, the crane day and the kitchen cost are typical national ranges from UK cost guides published during 2026. The planning fee is set nationally for England from 1 April 2026. The rules referred to are on the pages below.
Modular or traditional: questions
Is a modular extension cheaper than a traditional one?
Rarely by much. Per square metre the two bands are £2,100 to £3,300 for modular and £2,200 to £3,200 for brick and block, VAT included. The fees, the kitchen and the ground cost the same either way.
Where does modular actually save money?
In the costs that come from time: fewer weeks of disruption, less chance of a winter stoppage, and a price that is fixed before the factory starts rather than revised as the build goes on.
When is a traditional build better value?
When the shape is awkward, the access is poor, or the room is small. A crane day costs the same for 10 m² as for 40 m², and an L-shape or a curved wall suits bricks better than boxes.
Do the planning and building rules differ?
No. A modular extension needs the same planning route and the same building regulations approval as a brick one. In Scotland both need a building warrant before work starts.
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:
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