Homeowners planning a deck project in 2026 face two questions that matter above all others before any other decision can be made: what is this actually going to cost, and which material will give me the best return on that investment over the next decade or two?
The answers to both questions have changed significantly over the past five years, as premium timber species have become more accessible and the true cost of cheaper alternatives — factoring in maintenance and eventual replacement — has become more widely understood.
This article addresses both questions directly, covering the real cost of timber decking across species and specification options, and explaining why thermally modified ThermoWood with a secret fix installation system has become the preferred choice for homeowners who want to build once and maintain minimally.
What Timber Decking Actually Costs in 2026
The supply cost of timber decking varies significantly by species, with the difference between entry-level pressure-treated pine and premium ThermoWood typically in the range of £30 to £50 per square metre.
On a 20 square metre deck — a common size for a rear garden terrace or outdoor dining area — that difference is between £600 and £1,000 at supply.
Pressure-treated pine starts at approximately £25 to £35 per square metre depending on board dimensions and treatment system. Siberian larch — a naturally durable premium species — sits in the £45 to £65 per square metre range.
ThermoWood, depending on profile and whether a standard or secret fix board is specified, falls between £55 and £85 per square metre. Hardwood alternatives such as Garapa or Ipe are at the upper end of the market, from £80 per square metre upwards.
These supply costs represent only part of the total project cost. Installation typically adds £30 to £60 per square metre for labour, depending on whether the subframe needs to be constructed from scratch, how complex the elevation is, and whether hidden fixings are specified.
A complete installed deck on a straightforward rear garden application — ground-bearing, simple rectangular shape, standard subframe — commonly falls in the range of £1,500 to £4,000 for a 20 square metre area, depending heavily on species and fixing specification.
For a detailed breakdown of current timber decking supply costs by species, board width, and installation system — including honest whole-life cost comparisons between pressure-treated softwood and premium natural timber alternatives — the cost of timber decking per square metre UK guide provides the current market data needed to budget accurately before instructing a contractor or ordering materials.
ThermoWood Smooth Secret Fix Decking: Why the System Matters as Much as the Material
The choice of fixing system is one of the most consequential decisions in any deck project — and it is one that many homeowners only encounter when the work is already underway and the contractor is asking which way to go.
Understanding the difference between face-fixed and secret fix before the project begins produces better outcomes at lower long-term cost.
Face-fixed decking — the traditional approach where screws are driven through the top face of each board into the joist below — is faster to install and marginally cheaper in materials. But every screw hole is a moisture entry point that bypasses the surface protection of the timber.
Over time, fixing locations are where boards fail first — the timber around the screw becomes wet-compacted, the fixing head corrodes and stains the board surface, and eventually the fixing fails to hold the board flat. These failures begin invisibly and become visible problems typically within seven to ten years on standard softwood installations.
Secret fix systems eliminate this failure mode by using concealed clips that engage in grooves pre-machined into the sides of the boards. The clips hold each board flat to the joist without any penetration of the top face.
The result is a completely clean deck surface — no visible fixings, no corrosion staining, no moisture entry points at fixing locations — and a significantly longer service life at the most vulnerable structural points.
ThermoWood’s reduced moisture movement — a direct result of the thermal modification process that reduces moisture absorption by up to 50 percent — means the expansion gaps specified for the secret fix clips remain consistent across seasonal cycles.
On a standard softwood deck with hidden fixings, seasonal moisture movement can cause boards to bind against the clips or gap too widely depending on the season.
On a ThermoWood secret fix deck, this variation is substantially reduced, maintaining the clean appearance of the surface throughout the year.
For homeowners and contractors specifying a premium deck installation, ThermoWood smooth secret fix decking UK boards are available from UK stock in 26x140mm — the ideal width for residential deck applications.
Boards are pre-grooved for the BROfix hidden clip system. Full installation guidance, clip specifications, and joist centre recommendations are provided with every order.
Getting the Full System Right
The best deck installations treat material selection, fixing system, and subframe specification as a single coordinated decision rather than three separate choices.
ThermoWood secret fix boards on a correctly specified pressure-treated or naturally durable timber subframe, with stainless steel fixings throughout, adequate drainage fall, and correct ground clearance, produce an installation that will perform for 30 years or more with minimal active maintenance.
Annual inspection, cleared board gaps at the end of autumn, and a quality decking oil applied every two to three years to maintain the warm honey-brown colour if required — that is the complete maintenance commitment for a correctly installed ThermoWood secret fix deck.
For homeowners who have previously owned standard softwood decking and spent weekends on annual treating and board replacement, the difference is transformative.
The cost difference at installation is real but modest in the context of a complete outdoor project. The performance difference over the life of the deck is decisive.
