- Durability: Class 3 — naturally durable, no treatment required. 20–30 year service life above ground.
- Maintenance: None required structurally. Optional oiling every 1–2 years to maintain honey-gold colour. Weathers naturally to silver-grey without treatment.
- Profiles: Smooth 28x140mm, ribbed 27x142mm, grooved secret-fix 28x140mm, narrow smooth 28x90mm. All available from TCS with 7–14 day UK delivery.
- Cost: £25–45/m² supply only. Supply and install £55–90/m² all in. Higher than treated pine, lower whole-life cost than composite over 20 years.
- vs ThermoWood: Larch is naturally durable and less expensive. ThermoWood is Class 2 with longer service life and more consistent larch decking weathering UK grey tone — specify for zero-maintenance commercial or apartment decks.
- vs composite: Larch is natural, repairable, and FSC/PEFC certified. Composite requires no annual oiling but cannot be repaired. Whole-life costs are comparable.
- Installation: Minimum 5mm board gap for drainage. 150mm ground clearance. A4 stainless fixings throughout. Pre-drill all fixings.
Siberian larch decking is one of the most widely specified natural timber decking materials in the UK — a naturally Class 3 durable species that performs above ground for 20–30 years without preservative treatment, weathers gracefully to silver-grey, and offers the warmth and character of genuine natural timber that composite and pressure-treated softwood cannot replicate. This complete 2026 buyers guide covers everything you need to know before buying Siberian larch decking boards — profiles, sizes, durability, costs, installation, maintenance, weathering, and how larch decking compares to ThermoWood and composite alternatives.
Siberian larch smooth decking boards 28x140mm — the warm honey-gold of fresh Siberian larch decking. Naturally Class 3 durable, no preservative treatment required, 20–30 year service life. Left untreated, larch decking weathers to a clean silver-grey over 2–5 years. Oiled annually, it retains the fresh honey-gold character throughout its service life.
Why Siberian Larch Is One of the Best Decking Timbers UK
Siberian larch has been used for decking and exterior flooring across northern Europe for centuries — and its dominance in the UK premium decking market is based on genuine performance credentials rather than fashion. Three properties make larch the natural choice for UK decking:
- Natural Durability Class 3: Siberian larch contains naturally occurring resins that resist fungal decay and insect attack above ground. This natural durability — not chemical treatment — is what allows larch decking to perform for 20–30 years without preservative maintenance. Unlike Class 4 treated pine, larch does not rely on a treatment programme that lapses when maintenance is neglected
- Dimensional stability: Larch has lower moisture movement than most European softwoods — boards expand and contract less in response to UK weather changes, producing a more stable, gap-consistent deck surface over time. This stability is part of why larch decking holds its fixings well and does not develop the cupping and warping that affects lower-quality decking timbers
- Natural character: The warm honey-gold grain of fresh Siberian larch, and the dignified silver-grey it weathers to over time, are genuine natural material qualities that composite and pressure-treated pine cannot replicate. A larch deck has warmth underfoot (timber does not conduct cold the way composite and stone do) and a visual character that reads as quality at any viewing distance
Siberian Larch Decking Profiles UK — Which to Choose
Siberian larch ribbed decking boards 27x142mm — the ribbed profile provides anti-slip texture on the board surface, making it the preferred specification for decks that get wet regularly, around pools, or in shaded positions where moss and algae growth can reduce slip resistance on smooth boards.
The cleanest, most contemporary board profile — flat smooth face, square edges, consistent shadow between boards. Best for sheltered decks, covered areas, and anywhere slip resistance is not a primary concern. Shop smooth 28x140mm.
Machined ribs running the full board length provide anti-slip texture — the most widely used UK larch decking profile. Best for exposed decks, garden areas, and anywhere increased slip resistance is required. Shop ribbed 27x142mm.
Narrower board format for feature decking areas, decking patterns (herringbone, diagonal), or smaller deck areas where a finer board line is preferred. More boards per m² but tighter, more refined appearance. Shop narrow 28x90mm.
Premium grade larch decking with stricter knot and defect grading — cleaner, more consistent board faces with fewer large knots. Specified where a very clean, architectural board appearance is the design priority. Shop premium smooth.
Premium grade ribbed boards — the best of both worlds, anti-slip texture with stricter grading for a cleaner board face. The premium specification for exposed high-use decks where both performance and appearance are priorities. Shop premium ribbed.
Grooved boards for use with the Brofix hidden decking fastener system — no visible screw heads on the deck surface. The cleanest, most architectural decking installation. Higher cost due to the hidden fix system.
Siberian Larch Decking Weathering UK — What to Expect Over 5–30 Years
Siberian larch decking weathered to silver-grey — this is what untreated larch decking looks like after several years of natural weathering. The silver-grey is even, dignified, and requires no treatment to achieve or maintain. Many homeowners find the weathered grey more attractive than the fresh honey-gold starting point.
Understanding how larch decking weathers is one of the most important factors in making the right buying decision — and managing client or homeowner expectations correctly:
- Year 1: Fresh installation — warm honey-gold boards. Resin may bleed slightly at knots in the first summer — this is normal and weathers out. The deck looks fresh and golden
- Years 1–3: Weathering begins — boards start to grey from exposure. Different areas of the deck weather at different rates: exposed areas grey faster than sheltered areas, boards in direct sun grey faster than shaded boards. The deck may look patchy during this transition period — this is normal
- Years 3–5: Weathering stabilises — the full deck settles to a consistent silver-grey. The colour becomes even across the full deck surface as all areas reach a similar weathered state
- Years 5–30: Stable silver-grey character — the deck continues to perform structurally and the grey deepens slightly over time. No treatment required. Occasional cleaning (annual pressure washing or brush-down) maintains appearance
If you prefer the honey-gold to remain longer: apply a clear UV-protective decking oil on installation and re-apply every 1–2 years. See our Siberian larch decking maintenance guide for the full treatment programme and our timber oiling guide for product recommendations.
Siberian Larch Decking vs ThermoWood vs Composite UK
| Property | Siberian Larch | ThermoWood | Composite |
|---|---|---|---|
| Durability class | Class 3 | Class 2 | N/A — polymer |
| Service life | 20–30 years | 25–40 years | 20–25 years |
| Maintenance | Optional oiling 1–2 yrs | Zero | Wash annually |
| Natural material | Yes — genuine timber | Yes — modified timber | No — polymer/wood mix |
| Repairable | Yes — sand and re-oil | Yes — limited | No — replace boards |
| Warmth underfoot | Excellent — natural timber | Excellent | Poorer — can get hot |
| FSC/PEFC certified | Yes | Yes | Varies by brand |
| Supply cost (m²) | £25–45 | £40–60 | £30–80 |
| Whole-life cost (20 yrs) | Lower than composite | Lowest | Higher (no repair option) |
For the full comparison see our larch vs ThermoWood decking guide and our timber decking boards guide.
Siberian larch decking boards on pallet ready for nationwide delivery — TCS supplies Siberian larch decking boards in all profiles and sizes across the UK with 7–14 day delivery. FSC and PEFC certified chain of custody. All boards kiln-dried and planed to consistent finished dimensions.
How to Install Siberian Larch Decking UK
Correct installation is as important as board quality for long-term larch decking performance. The key installation requirements:
- Sub-frame: 47x100mm or 47x150mm C24 treated softwood joists at maximum 400mm centres for 28mm boards. Joists must be level and in the same plane — an uneven sub-frame produces a bouncy or undulating deck surface
- Ground clearance: Larch decking ground clearance UK — minimum 150mm between the underside of the decking boards and finished ground level — this ensures adequate airflow beneath the deck to prevent moisture buildup. On ground-level decks where 150mm is difficult to achieve, ensure the ground below is well-drained gravel or membrane rather than bare soil
- Board gaps: Minimum 5mm gap between boards — 6–8mm for boards installed during wet conditions (timber will shrink as it dries down). Consistent gaps are important for both drainage and appearance. Use a spacer board or timber off-cut to maintain consistent gap width
- Fixings: A4 stainless steel decking screws throughout — never galvanised or zinc-plated. Two screws per board per joist for 140mm+ wide boards. Pre-drill all fixings to prevent splitting. For secret fix larch decking UK, use the Brofix hidden fastener system with grooved boards
- Board orientation: Run boards at 90° to the joists. Where joists run parallel to the house, boards run perpendicular (away from the house) — this is the standard orientation that produces the most structurally sound and visually clean result
- End grain sealing: Apply end grain sealant or decking oil to all cut ends immediately after cutting — end grain absorbs moisture significantly faster than face grain and is the most vulnerable point in any decking board. This is particularly important on cut board ends at the perimeter of the deck
See our full how to build a deck UK guide for the complete step-by-step installation sequence, sub-frame specification, and joist sizing guide.
Siberian Larch Decking Cost UK — 2026 Prices
| Profile | Supply only (m²) | Supply & install (m²) | Typical 20m² deck |
|---|---|---|---|
| Smooth 28x140mm | £28–38/m² | £55–80/m² | £1,100–1,600 |
| Ribbed 27x142mm | £30–40/m² | £58–85/m² | £1,160–1,700 |
| Smooth 28x90mm (narrow) | £32–42/m² | £60–88/m² | £1,200–1,760 |
| Premium smooth 28x140mm | £35–48/m² | £65–95/m² | £1,300–1,900 |
| Secret fix grooved | £38–52/m² | £70–100/m² | £1,400–2,000 |
All supply-and-install prices include sub-frame, fixings, and basic perimeter finishing. See our full Siberian larch cost guide and our timber decking cost per m² UK 2026 guide for detailed pricing breakdowns.
Timber decking extends the living space of a house into the garden — natural larch decking consistently adds value to UK properties, particularly where the deck creates a usable outdoor living area that connects to the interior living space through bifold or sliding doors.
Larch decking add value UK — yes, a well-specified and well-installed larch deck consistently adds value to UK residential properties. The addition of a usable outdoor living space connected to the interior adds perceived and measurable value — estate agents and surveyors typically value quality decking at 50–80% of its installation cost in added property value. Natural timber decking reads as a quality specification compared to treated pine panels or composite, and the zero-maintenance credentials of naturally durable larch are increasingly valued by buyers aware of the ongoing maintenance obligations of treated softwood alternatives. See our does decking add value guide for the full picture.
How long does Siberian larch decking last UK?
20–30 years above ground with zero preservative treatment — naturally Class 3 durable. Correctly installed with 150mm ground clearance, adequate ventilation, and 5mm board gaps, larch decking performs structurally for 20–30 years without treatment. Optional oiling maintains appearance but has no structural benefit.
Does Siberian larch decking need treating UK?
No — naturally Class 3 durable, zero treatment required structurally. Optional clear UV oil every 1–2 years maintains the honey-gold colour. Without treatment, larch weathers to an even silver-grey over 2–5 years and continues to perform for 20–30 years. Unlike treated pine, larch does not structurally deteriorate without a treatment programme.
How much does Siberian larch decking cost UK?
£28–48/m² supply only depending on profile and grade. Supply and install £55–100/m² all in for a typical residential deck. A typical 20m² larch deck costs £1,100–2,000 all in. Higher upfront than treated pine but lower whole-life cost — zero maintenance, 20–30 year service life, repairable by sanding and re-oiling.
Is Siberian larch decking better than composite UK?
For most residential gardens, yes. Larch is natural timber with genuine warmth underfoot, repairable by sanding, FSC/PEFC certified, and naturally durable without chemical additives. Composite requires no annual oiling but cannot be repaired — damaged boards must be replaced. Whole-life costs are comparable over 20 years. Larch weathers naturally and ages gracefully; composite maintains its original appearance but can fade unevenly.
What is the best Siberian larch decking profile UK?
Ribbed 27x142mm for most exposed residential decks — the ribbed profile provides anti-slip texture for safety when wet. Smooth 28x140mm for sheltered or covered decks where slip resistance is less critical and a cleaner contemporary appearance is preferred. Premium grade for either profile where a very clean board face with fewer knots is the design priority.
Siberian Larch Decking — Supply UK Wide, 7–14 Days
We supply Siberian larch decking boards in smooth, ribbed, premium, and secret-fix grooved profiles across the UK. FSC and PEFC certified. Kiln-dried and planed to finished dimensions. All profiles in stock for 7–14 day nationwide delivery. Contact us for a quote or order online.