Usually, in uPVC or aluminium. A uPVC orangery typically costs well under a single-storey extension of the same size, aluminium a little under, and hardwood lands in much the same band. The frames and the lantern decide it.
People often assume an orangery is the budget version of an extension. It can be, but the two overlap far more than the names suggest, and in a hardwood specification the orangery saves little or nothing.
The typical figures
As typical national ranges for 2026, with VAT included:
| Room | Per m² | A 20 m² room |
|---|---|---|
| Single-storey extension, standard spec | £1,800 to £3,000 | £36,000 to £60,000 |
| Orangery, uPVC frames | £850 to £2,000 | £17,000 to £40,000 |
| Orangery, aluminium frames | £1,600 to £2,500 | £32,000 to £50,000 |
| Orangery, hardwood frames | £2,000 to £3,000 | £40,000 to £60,000 |
London and the South East usually cost 20 to 40% more. These are a guide, not a quote.
Why the two cost so nearly the same
Below the windowsills they are the same building. Both need foundations to the depth building control asks for, an insulated floor slab, drainage and a connection to the house. Both have an insulated flat roof. None of that gets cheaper because the room is called an orangery.
The differences are above the sill. An extension has more brick and less glass, and brickwork is cheaper per square metre than good glazing. An orangery swaps wall for tall windows and adds a roof lantern, which a plain extension does not have. In uPVC the glazing is inexpensive enough that the orangery comes out well ahead. In hardwood it does not, and the two rooms cost much the same.
Where an orangery saves money
Not on paperwork. A solid roof keeps an orangery out of the conservatory exemption, so it goes through building control just as an extension does, with the same fee and the same insulation standards for the walls, floor and deck.
The saving, where there is one, is in the walls. In uPVC, a run of standard-size frames can cost less than the brickwork, insulation, render and windows of an equivalent extension wall.
Orangery builders also tend to work from standard frame systems and lantern sizes. If your room fits one, the design cost is low.
Where an extension saves money
Open the room to the kitchen and both routes need full building regulations approval and a steel beam over the opening. The orangery then has a harder job meeting the energy rules, because glazing beyond 25% of the floor area must be justified by calculation. That usually means better glass and more roof insulation, and the cost rises towards the extension’s.
An extension is also the cheaper way to get a room with a lot of usable wall, for a utility, a bathroom or a kitchen with long runs of tall units.
How to choose between them
Ask what the room is for. If daylight and the view of the garden are the point, an orangery gives you more of both for similar money. If you need walls, privacy from neighbours or a bedroom above later, build the extension.
Then get both priced. Builders who do one usually do the other, and the difference on your site may be smaller than any national average suggests. Our orangery cost calculator will give you a starting range for the orangery side of that comparison.
Sources and how the figures are worked out
Rules are for England unless the text says otherwise, and are general guidance. Your council decides for your house.