Planning a Garden Room in 2026? Here's What the Cladding Actually Costs
Garden rooms have become one of the most popular home improvement projects in the UK and for good reason. A well-built, well-insulated garden room adds usable space, improves working-from-home quality, and contributes meaningfully to property value. But the costs involved are not always straightforward, particularly when it comes to the exterior finish. Cladding is one of the areas where quoted prices vary most dramatically between suppliers and installers, and where the wrong choice can create significant ongoing costs long after the build is complete.
If you are planning a garden room project in Devon or the South West, understanding what exterior cladding actually costs — and why the cheapest option is rarely the best value — is the most useful research you can do before instructing a contractor or placing a materials order.
Why Cladding Costs Vary So Much
Cladding costs vary significantly by species, profile, grade, and finishing treatment. The supply cost for the boards themselves ranges from as little as £15 per square metre for basic Nordic spruce shiplap through to £90 or more per square metre for premium charred timber profiles. The most commonly specified mid-range options — Siberian larch and thermally modified ThermoWood — fall in the £30 to £65 per square metre range depending on profile and grade.
Installation costs add a further £25 to £60 per square metre for labour, depending on elevation complexity, the fixing system specified, and whether a new subframe and membrane are required. Simple rectangular elevations with no openings or reveals are at the lower end. Elevations with multiple windows, complex reveals, or hidden fixing systems are at the upper end.
The decision that most significantly affects long-term cost is species selection. Pressure-treated pine is the cheapest supply option but carries the highest long-term cost: annual or biannual retreating at £8 to £15 per square metre, periodic board replacement at fixing points, and a visual deterioration timeline that begins at year three to five without consistent maintenance. Naturally durable or thermally modified species cost more upfront and eliminate or dramatically reduce that ongoing cost for the full service life of the building.
On a typical 30 square metre garden room with 60 square metres of total clad elevation, the supply cost difference between basic treated spruce and premium ThermoWood is approximately £1,500 to £2,500. The elimination of retreating costs over ten years typically exceeds £1,000 at current labour rates, making the premium effectively self-funding within a decade. Beyond ten years, naturally durable timber is genuinely cheaper to own.
For a detailed breakdown of current timber cladding supply and installation costs across all main species — including ThermoWood, Siberian larch, Nordic spruce, charred timber, and Douglas fir — with guidance on calculating quantities, understanding grade differences, and budgeting accurately for the complete external finish of a garden room or extension, the Timber Cladding Specialists guide provides a comprehensive cost reference for homeowners planning a garden building project in 2026.
What to Ask Your Contractor
Most garden room contractors will quote a cladding specification without fully explaining why they have chosen that species and profile. The questions worth asking before accepting any quote are: what species is the cladding, what is the durability class, does it require treatment and if so how often, what fixing system is being used, and what is the cavity depth behind the boards.
The answers to these questions tell you whether the specification is designed for long-term performance or lowest upfront cost. A contractor who specifies a ventilated rainscreen system with stainless steel fixings and a naturally durable or thermally modified species is designing for the building's full service life. A contractor who specifies untreated spruce face-fixed directly to the frame is minimising their material cost at your long-term expense.
For specialist advice on species selection, profile choice, and installation requirements for any garden room or exterior cladding project — and for supply of all main timber cladding species from UK stock with nationwide delivery including Devon and the South West — Timber Cladding Specialists provides technical guidance alongside supply, with samples available before ordering and full installation documentation with every order.
Getting the Most from Your Garden Room Investment
The garden rooms that hold their value best and generate the most satisfaction over the years are those where the external finish was specified for quality from the outset. A building clad in naturally durable timber, installed in a correctly detailed rainscreen system, with appropriate ground clearance and stainless steel fixings, will look right and perform correctly for 25 to 30 years with minimal active maintenance. That longevity is what makes a garden room a genuine asset rather than a liability that requires remedial work within a decade of completion.
