It is the first question most people ask. It is the last question we can answer meaningfully — because a price without a specification is not a price, it is a number that will mislead you in one direction or the other. This article explains what drives the cost of a timber frame commission, provides some honest indicative ranges, and tells you what the right way to get an accurate number actually is.
What drives cost
Species
Oak costs roughly twice what Douglas Fir costs for equivalent structural grades. This is not a small difference. For a garden room frame where the timber will be largely enclosed, paying the oak premium produces no material benefit. For a traditional exposed extension frame where the posts and knee braces are the visual centrepiece of the room, oak is the correct material and the premium is justified. We recommend the right species for the application. They grow both, so they have no commercial incentive to push you toward the more expensive one.
Complexity
A simple box frame — four walls, a ridge, principal rafters — is the baseline. A cruck frame, where curved principal members rise from ground to ridge in a single piece, requires sourcing timber with the right natural curve and considerably more hand work to prepare. A raised aisle frame — with aisles extending beyond the principal posts under a continuous roof — is a more complex structural system with more joints and more engineering. Complexity drives cost in two ways: more components and more time per component.
Decorative complexity also adds cost. Curved knee braces are more expensive than straight ones. A chamfered stop on an arris costs workshop time. Pegged joints are slower than bolted ones. None of these details is wasteful — they are what distinguishes traditional framing from structural steel with a wooden face. But they cost time, and time costs money.
Size
The relationship between size and cost is not linear. Design time, engineering, and setup costs are largely fixed regardless of frame size — a 3×3m garden room and a 5×4m garden room require similar amounts of design and engineering work. Material cost scales with volume. Fabrication time scales with component count, which is roughly proportional to area but with diminishing marginal cost as the frame gets larger — the same CNC setup runs a longer cutting list at minimal additional overhead. In practice, larger frames are proportionally cheaper per square metre than smaller ones, because the fixed costs are amortised across more material.
Access
A straightforward site — flat, good vehicle access, telehandler can reach the foundation without difficulty — is the baseline for delivery and raising. A constrained site adds cost. A garden accessible only through a 2m gate requires the frame to be delivered in sections small enough to pass through it and assembled on site rather than pre-assembled and craned in. A steep hillside requires different machinery or more people. Access constraints are not reasons to decline a project; they are factors that need to be assessed at site visit and priced accordingly.
Finishes
Green oak left natural is the cheapest finish — nothing applied, nothing maintained. Kiln-dried oak with an oiled finish requires more drying time before it leaves the workshop and adds a material and labour cost for the oil treatment. Painted softwood windows and doors require priming, undercoating, and top coating at the workshop before installation. Each finish has an appropriate cost, and the right finish depends on the application rather than the budget — you would not leave painted joinery unprimed to save money, because it would fail within two years.
Indicative ranges
These are rough figures only. They assume typical complexity, good site access, and standard finishes. Any particular project may be significantly higher or lower depending on the factors above.
- Oak garden room, 4×3m structural frame only: Pricing depends on species, dimensions, and project complexity. Contact the workshop for a detailed quote.
- Oak single-storey rear extension, standard three-bay: Pricing depends on species, dimensions, and project complexity. Contact the workshop for a detailed quote.
- Douglas Fir equivalent — garden room or extension at similar size: Pricing depends on species, dimensions, and project complexity. Contact the workshop for a detailed quote.
- Oak entrance porch, two-post: quoted per project — typically the most accessible entry point
These ranges do not include groundworks, foundations, infill panels, glazing, roofing, or any services installation. They cover design, materials, fabrication, trial assembly, and delivery and raising to a reasonable distance from Welshpool.
Why kit frames are cheaper
A kit oak frame from a large manufacturer costs less than a commission from us for the same floor area. The reason is production economics, not quality competition. A kit manufacturer designs a standard frame once and produces it thousands of times. The design cost is amortised across the production run. The components are cut to a standard specification and the joints are standardised. What you receive is a product — well-designed for what it is, but not designed for your site, your planning context, or your brief.
We do not compete with kit frames on price. They compete on what a bespoke commission provides: design specific to your site, timber from a known source, fabrication by the people you spoke to, trial assembly before delivery, and a direct line back to the workshop when anything needs attention after installation. For clients who need a structure quickly and at minimum cost, a kit frame is a legitimate option. For clients who want something built for them rather than bought off a shelf, the Citadel process is the answer.
What the price includes
A Citadel quotation covers: initial site visit and consultation, structural design and working drawings, structural engineering coordination (engineering fee is usually a separate cost quoted by the engineer directly), all materials from our own woodland where applicable, fabrication at the Welshpool workshop, trial assembly in the workshop yard, and delivery and raising to within a reasonable radius of the workshop. Client visits during fabrication and at trial assembly are included — they are part of how Citadel works, not extras.
What it does not include
Groundworks and foundations are outside our scope. The foundation must be complete and to level before the frame arrives. Infill panels — SIPs, studwork, cladding — are usually outside scope unless specifically agreed. Glazing supply and installation is outside scope (Citadel designs the structural opening; a glazing contractor installs the unit). Roofing is outside scope. Services — electrical, plumbing, heating — are outside scope. These are straightforward to coordinate through a main contractor or directly with specialist subcontractors, and the sequencing is logical: Citadel raises the frame, others enclose it and fit it out.
How to get an accurate number
There is no shortcut. Describe your project to Citadel: what you want to build, where it sits, what your planning context is, and what budget you have available. Citadel will visit the site, assess the brief, and produce a quotation to a specific scope. That quotation is the accurate number. An online calculator, a ballpark from a friend who had an extension, or a figure extrapolated from a rate per square metre will all mislead you — timber frame pricing depends too heavily on the specific variables of your project. The consultation is free. The quotation is free. The only cost is the time of the site visit.