Oak Frame Extension Cost
A finished oak frame extension typically costs £2,400 to £3,500 per square metre including VAT. Set the type, size and level of detail below to see a range for your own room, then send it to a framer for a real price.
Cost calculator
Typical cost to build, including VAT
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A guide, not a quote. Includes foundations, the oak frame, roof, glazing, plastering and electrics. Leaves out design fees and kitchens. London and the South East usually cost 20 to 40% more.
Prices by size
These figures are for a single-storey oak framed room on ordinary ground, built and finished: foundations, plinth, frame, roof, glazing, insulation, electrics, plaster and floor.
Below 15 m² the rate rises by about a tenth, because design, scaffolding, crane hire and setting up on site cost nearly the same for a small room as for a large one.
A guide, not a quote. National figures, including VAT.
Where these figures come from
Typical national ranges for 2026, including VAT. London and the South East usually cost 20 to 40% more. Bespoke oak work can exceed £3,500 per m². A guide, not a quote.
| Floor area | Simple | Detailed | Elaborate |
|---|---|---|---|
| 15 m² | £36,000 to £42,000 | £42,000 to £48,000 | £48,000 to £52,500 |
| 20 m² | £48,000 to £56,000 | £56,000 to £64,000 | £64,000 to £70,000 |
| 25 m² | £60,000 to £70,000 | £70,000 to £80,000 | £80,000 to £87,500 |
| 30 m² | £72,000 to £84,000 | £84,000 to £96,000 | £96,000 to £105,000 |
| 40 m² | £96,000 to £112,000 | £112,000 to £128,000 | £128,000 to £140,000 |
| 50 m² | £120,000 to £140,000 | £140,000 to £160,000 | £160,000 to £175,000 |
What moves the price
How much oak is on show. Trusses and wall posts in oak with softwood rafters hidden above the ceiling is the economical way to build. Oak rafters, purlins and curved braces throughout can add a fifth to the frame.
Glass. Rectangular units between posts are standard sizes. A gable glazed to the ridge needs raked units made to a template, and structural glass doors cost more again.
The roof. Handmade clay tiles and lead cost more than machine-made tiles and a membrane. A lantern in a flat roof costs more than either.
The ground. Clay near trees, made-up ground or a sloping site can turn a simple strip foundation into a deeper or piled one. Nobody can price that until the ground is investigated: your engineer designs and prices piles after a ground investigation, and they can add several thousand pounds.
Access. The frame arrives on a lorry and is lifted by a small crane. If neither can reach the back of the house, the timbers are carried through by hand and the raising takes longer.
The house. A listed building adds drawings, a heritage statement and often a slower programme. See the pages on oak orangeries, garden rooms and kitchen extensions for what each type involves.
Rates by type of room
| Type | Simple to elaborate, per m² |
|---|---|
| Single-storey room | £2,400 to £3,500 |
| Garden room | £2,400 to £3,500 |
| Kitchen extension | £2,500 to £3,500 |
| Orangery | £2,500 to £3,500 |
| Brick and block, for comparison | £1,800 to £3,000 |
Fees to allow on top
| Item | Typical cost |
|---|---|
| Architect or designer, planning drawings | £1,000 to £2,500 |
| Structural engineer, single storey | £600 to £1,200 |
| Building control, single storey of 10 to 40 m² | £700 to £1,100 |
| Party wall surveyor, per neighbour, one agreed surveyor | £700 to £1,500 |
| Householder planning application, England | £548 |
| Lawful development certificate, England | £274 |
| Listed building consent | No fee |
| VAT on the build | 20% |
Where the fees and rules come from
Professional fees are typical national ranges for 2026, including VAT; an architect on a full service usually charges 3% to 15% of the build cost. The party wall figure assumes one surveyor agreed by both sides; if your neighbour appoints their own, you pay for both. Planning fees are set by MHCLG from 1 April 2026. Scotland, Wales and Northern Ireland set their own.
A range is a start. A framer who has seen the house can give you a price.
Get a quoteA worked example
Take a 24 m² oak frame garden room, 6 m by 4 m, at a detailed specification: two king post trusses, a glazed gable, underfloor heating and clay tiles.
At £2,800 to £3,200 per m² the build comes to £67,000 to £77,000. Add planning drawings and a structural engineer at £1,600 to £3,700, building control at £700 to £1,100 and a planning fee of £548. Including VAT that is roughly £70,000 to £82,500.
VAT at 20% applies to the building work and to most professional fees, though not to the planning fee, and is included in these figures. Furniture, blinds, landscaping and making good the garden after the builders leave are not in these figures.
Where the money goes
People are often surprised that the oak is not the largest item. On a typical job the frame, cut and raised, is around a quarter to a third of the total. Groundworks and the floor slab take a similar share on difficult ground and less on easy ground. Glazing is the next largest, then the roof. Electrics, plastering, flooring and decoration make up the rest.
That split explains why trimming the oak rarely saves much. Dropping from three trusses to two might take a few thousand pounds off a job that still needs the same foundations, the same roof and the same glass. Reducing the glazed area, or choosing a simpler roof covering, usually saves more.
Paying for it in stages
Oak framers normally ask for a deposit when the frame is ordered, a second payment when cutting starts and the balance when the frame is raised. The general builder is paid separately against stages of work. Before you pay any deposit, ask what happens to it if planning is refused, and get the answer in the contract.
Questions about cost
How much does an oak frame extension cost per m²?
As a national guide, £2,400 to £3,500 per square metre for a finished single-storey room, including VAT; bespoke work can cost more. Orangeries and heavily glazed garden rooms sit towards the top; a plain room with softwood rafters and modest glazing sits at the bottom.
Why does oak cost more than brick and block?
The timber is a small part of it. Most of the premium is skilled workshop time cutting joints by hand, made-to-measure glazing fixed to the face of the frame, and the extra design work needed to allow for a structure that shrinks as it dries.
How much of the price is the oak frame itself?
Commonly somewhere between a quarter and a third of the finished cost. Foundations, the roof, glazing, insulation, electrics and plastering cost much the same whatever holds the roof up.
Is it cheaper to buy the frame and manage the build myself?
It can be, if you have the time and a builder who has worked round green oak before. You take on the risk where the trades meet: plinth levels, glazing sizes and weathering.
Do oak frame extensions cost more to maintain?
No. The frame needs nothing. Budget for a return visit after a year or two to re-seal joints that have opened as the oak dried, which a good builder includes.
Are these prices the same across the UK?
They are national figures. Expect London and the South East to run 20 to 40% higher, and remote sites to carry extra for delivery and crane hire.
Get a quote for your oak frame
Three short steps: the postcode, four questions about the build, then how to reach you.
This is a free introduction service, not an oak frame specialist. We find a firm that frames in oak near you and tell you its name. Your details stay with us until you say yes.
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- We look for an oak framer who takes on this kind of build in your area, then email or phone you with the firm's name.
- Nothing is passed on unless you say yes to that firm.
- They visit, look at the house and price the work. We never send marketing.