Oak framed extensions are the single most-requested service we quote each month, and costs have shifted noticeably over the last two years. Timber prices, labour rates, energy regulations and glazing specifications have all changed. Here is an up-to-date, honest breakdown of what an oak framed extension really costs in 2026, based on the projects we build across Sussex, Surrey and Kent.
Oak Framed Extension Cost at a Glance (2026)
| Specification | Per m² | Typical 30 m² Project |
|---|---|---|
| Shell only (frame & foundations) | £1,600 – £2,200 | £48,000 – £66,000 |
| Supply & install (weathertight) | £2,400 – £3,200 | £72,000 – £96,000 |
| Fully finished turnkey | £3,500 – £5,000 | £105,000 – £150,000 |
Where the Money Goes
On a typical £90,000 single-storey oak framed extension, the split of costs looks roughly like this:
- Design, planning & building control — 6%
- Foundations & groundworks — 12%
- Oak frame (manufacture + raising) — 22%
- SIP encapsulation & roof — 18%
- Glazing, doors & bi-folds — 14%
- Plastering, flooring, internal finishes — 14%
- M&E (plumbing, electrics, heating) — 9%
- Contingency & fees — 5%
The Factors That Push Cost Up
Complexity of the Tie-In
Tying a new oak frame into an existing period property — particularly one with cob walls, flint, or timber framing — requires more design work and more careful structural detailing. Expect an extra 8–15% over a simple tie-in to a standard brick cavity wall.
Glazing Ratio
Modern oak framed extensions often feature huge bi-fold or slide-and-turn door systems. Premium aluminium bi-folds cost £700–£1,100 per linear metre installed. A glazed gable with bespoke fixed glass and oak mullions runs from £8,000–£20,000 depending on size.
Roof Specification
Handmade clay tiles, natural slate or cedar shingles all add character — and cost. Budget an extra £25–£80 per square metre of roof area over a standard machine-made tile.
Site Access
Restricted access sites add time and sometimes require crane hire for the frame raising. Cranes typically cost £1,200–£2,500 per day.
Listed Buildings & Conservation Areas
Listed building consent, heritage statements and specialist architectural input can add £4,000–£8,000 to the professional fees and often drive higher material specifications.
Oak Framed Extension vs Brick Extension
As a rule of thumb, expect to pay a 10–20% premium over a like-for-like brick extension. What you get in return is the architectural drama of exposed oak beams internally, better thermal performance with SIP encapsulation, and a significantly faster build on site.
How to Keep Costs Under Control
- Get a proper site survey first. A detailed survey reveals ground conditions, services, and structural realities that often dictate foundation cost.
- Lock down glazing specification early. Changes to glazing are one of the single biggest sources of scope creep on extension projects.
- Use SIP encapsulation. Kingspan TEK or equivalent SIPs dramatically cut heat loss and speed the build compared with traditional stud-and-insulation infill.
- Treat the oak frame as the focal point. If the frame is the hero of the room, you can save significantly on internal finishes without the space feeling cheap.
- Build in a sensible contingency. 5–10% contingency is industry standard; we recommend 10% on older properties.
Get an Accurate Quote for Your Project
No two sites are the same, and online calculators can only take you so far. If you want a detailed, honest quote for an oak framed extension at your home, book a free consultation and our team will come out, survey the property, and produce a fixed-fee proposal within 10 working days.
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Frequently Asked Questions
How much does an oak frame extension cost in 2026?
Typically £2,800–£4,500 per m² fully installed, with small extensions starting from £45,000 and large double-height kitchens reaching £180,000+.
Is an oak framed extension more expensive than brick?
Typically 10–20% more — the premium pays for the oak frame, exposed beams and SIP thermal performance.
Do I need planning permission for an oak framed extension?
Many fall under permitted development, but larger, front, conservation area or listed building projects require full planning consent.
How long does an oak framed extension take to build?
Typically 14–20 weeks from planning approval to completion.
