Quick Answer
For most UK construction projects, C24 graded Scandinavian spruce or pine is your best structural timber. It costs around £350 to £500 per cubic metre, handles load-bearing work, and is readily available from any decent timber merchant. Use C16 for non-structural work like stud walls. For exterior projects, European larch or treated softwood will last decades without rotting. If you need serious strength or long spans, engineered options like glulam or CLT outperform solid timber every time.
Table of Contents
- Why timber selection matters more than ever
- Softwood species guide
- Hardwood species guide
- Engineered timber products
- Timber grading explained: C16, C24, and TR26
- Durability classes and timber treatment
- Softwood vs hardwood vs engineered: the full comparison
- Best timber for common UK projects
- Fire safety and building regulations
- Where to buy timber in the UK
- Timber construction in action
- What tradespeople are saying
- Frequently asked questions
Why timber selection matters more than ever
The UK construction industry uses over 10 million cubic metres of timber every year, and costs have been on a rollercoaster since 2020. The Timber Development UK structural timber price index hit record highs during the pandemic supply crunch, and while prices have settled, they remain well above pre-2020 levels. Getting your timber selection right saves money, prevents callbacks, and keeps projects on schedule.
Picking the wrong species or grade costs you twice. Once when you buy it, and again when it fails. Untreated softwood in ground contact will rot within five years. C16 timber in a load-bearing beam can crack under stress. The wrong hardwood in a bathroom will warp within months. Every timber choice comes down to three factors: what load does it carry, what moisture will it face, and what does the client expect it to look like.
UK Timber Market 2026
Building material costs are expected to rise 2.5 to 3.5 per cent across 2026 according to industry forecasts. The TDUK structural timber price index fell to 125 by Q3 2025 after the pandemic spike, but US-Canada trade disputes and low sawmill stocks continue to create pricing pressure. Lock in prices early on large orders.
Softwood species guide
Softwood accounts for the vast majority of construction timber used in the UK. It grows faster than hardwood, costs less, and is easier to work with. Most structural softwood sold in the UK comes from Scandinavia, the Baltics, or Scotland. Here are the species you will encounter most often.
Scots pine (European redwood)
The workhorse of UK construction. Scots pine is the most widely used softwood in the UK window, door, and joinery industry. It takes preservative treatment well, making it suitable for exterior use when properly treated. The heartwood has a natural durability class of 4 (slightly durable), meaning it needs treatment for any exposed application. Expect to pay around £300 to £450 per cubic metre depending on grade and finish.
Sitka spruce (European whitewood)
Sitka spruce is the most planted tree species in UK forests and makes up a large proportion of domestically grown construction timber. It is lighter and less dense than pine, with a durability class of 5 (not durable). It does not take treatment as well as pine because of its lower permeability. Sitka spruce is commonly used for internal structural work, stud walls, and roof trusses where moisture exposure is minimal.
European larch
Larch is the toughest softwood commonly available in the UK. UK-grown larch has a durability class of 4, which is better than most softwoods. It is naturally more resistant to moisture and can be used externally without treatment for cladding, fencing, and garden structures. Larch develops an attractive silver-grey patina over time when left untreated outdoors. It costs more than pine or spruce but saves on treatment costs for exterior work.
Douglas fir
Douglas fir offers excellent strength-to-weight ratio and is commonly used for large structural members. UK-grown Douglas fir has a durability class of 4. It is popular for exposed beams and timber frame construction where both strength and appearance matter. The distinctive reddish-brown colour and straight grain make it an attractive choice for visible structural elements.
Buying tip: check the stamps
When you order C24 timber, check the grading stamps on every piece before the delivery driver leaves. Timber merchants have been known to slip C16 pieces into C24 orders. The stamp is on the end grain and shows the grade, the certification body, and the sawmill code. If it says C16, send it back.
Hardwood species guide
Hardwoods cost more and take longer to grow, but they offer superior durability, strength, and appearance for the right applications. In UK construction, hardwoods are typically used for high-end joinery, structural green oak frames, flooring, and exterior features where longevity justifies the premium.
European oak
Oak is the king of UK hardwoods. With a durability class of 2 (durable), oak heartwood will last decades outdoors without treatment. Green oak timber framing is a premium construction method with a history spanning centuries. Air-dried structural oak costs around £1,200 to £1,800 per cubic metre. Kiln-dried joinery oak costs even more. Oak is heavy to work with and requires carbide-tipped tools due to its high tannin content, which corrodes standard steel fixings.
Sweet chestnut
Often overlooked in favour of oak, sweet chestnut shares durability class 2 and offers similar rot resistance at a lower price point. It grows widely in southern England and is excellent for fencing, cladding, and outdoor furniture. Sweet chestnut cleaves easily, making it ideal for traditional cleft fencing. It typically costs 15 to 25 per cent less than equivalent oak.
European ash
Ash is strong and flexible, making it excellent for tool handles, sports equipment, and steam-bent furniture. However, it has a durability class of 5 (not durable) and is completely unsuitable for exterior use without treatment. The ongoing ash dieback disease (Hymenoscyphus fraxineus) has devastated UK ash populations, making supply increasingly scarce and pushing prices upward.
European beech
Beech is a dense, hard timber with excellent machining properties. Like ash, it falls into durability class 5 and must be kept dry. It is widely used for furniture, worktops, and interior joinery. Beech takes stain and finish well, making it popular for fitted kitchens and bespoke furniture work.
Engineered timber products
Engineered timber is manufactured by bonding layers, strands, or veneers of wood together under pressure. The result is stronger, more dimensionally stable, and more predictable than solid timber. Engineered products are transforming UK construction, with the Government's Timber in Construction Roadmap 2025 actively promoting their use.
Cross-laminated timber (CLT)
CLT panels are made from layers of solid timber boards glued at 90-degree angles to each other. This cross-lamination gives CLT strength in both directions. Panels can be manufactured up to 3.5 metres wide and 16.5 metres long. CLT is increasingly used for walls, floors, and roofs in UK buildings up to 18 metres tall. The Black and White Building in Shoreditch, London, is a prominent UK example of CLT construction.
Glued laminated timber (glulam)
Glulam beams are made by bonding multiple layers of dimensioned timber together. They can span further than solid timber, with beams manufactured up to 30 metres or more. Glulam is commonly specified for exposed structural beams, sports halls, and commercial buildings where long clear spans are needed. It complies with BS EN 14080.
I-joists (JJI-Joists)
JJI-Joists are the most widely specified engineered wood product in the UK. They use an OSB web with solid timber flanges, creating a lightweight joist that spans further than solid timber of the same depth. I-joists are standard in modern timber frame construction for floors and flat roofs. They are faster to install and reduce waste compared to solid timber joists.
Laminated veneer lumber (LVL)
LVL is made from thin wood veneers bonded together under heat and pressure. It offers consistent strength properties with no natural defects like knots or splits. LVL is used for beams, headers, and rim boards where high strength is required in a compact section. It is particularly useful where you need maximum strength from minimum depth.
Cost comparison: timber frame vs masonry
Timber frame construction in the UK typically costs between £1,800 and £2,500 per square metre in 2026. While the material cost can be higher than traditional masonry, the faster build time (often 30 to 40 per cent quicker) reduces labour costs and gets you to a watertight shell sooner. For self-builders, timber frame often works out cheaper overall.
Timber grading explained: C16, C24, and TR26
Every piece of structural timber sold in the UK must be strength graded to BS EN 14081. The grade tells you how much load the timber can safely carry. Get this wrong and you risk structural failure. Get it right and you can spec confidently without over-engineering.
How grading works
Timber is graded using two methods. Visual stress grading involves a trained inspector assessing visible characteristics like knots, grain slope, and rate of growth against the requirements of BS 4978 (softwoods) or BS 5756 (hardwoods). Machine stress grading uses automated systems that measure bending stiffness through vibrations and ultrasound scanning, combined with visual assessment of knots and grain. Machine grading is more accurate and consistent.
C16 vs C24: the key differences
The "C" stands for conifer (softwood). The number indicates the characteristic bending strength in megapascals (MPa). C16 has a bending strength of 16 MPa and a minimum density of 310 kg per cubic metre. C24 has a bending strength of 24 MPa and a minimum density of 350 kg per cubic metre. That 50 per cent strength increase matters.
C16 is predominantly UK-grown timber. It is cheaper and more readily available but is only suitable for non-load-bearing work like stud partitions, internal framing, and general carpentry. C24 is mostly imported from Scandinavia and Germany where slower growth produces tighter grain and fewer defects. C24 is the standard specification for floor joists, roof rafters, and any load-bearing structural element.
TR26: the roof truss grade
TR26 is the strongest structural softwood grade used in the UK, exclusive to trussed rafter fabricators. It has a bending strength of 26 MPa. You will not find TR26 at a builders merchant because it is only available through truss manufacturers who machine-grade every piece. If your structural engineer specifies TR26, the trusses must come from an approved fabricator.
Do not substitute C16 for C24
If a structural engineer specifies C24, you must use C24. Using C16 as a cheaper alternative in a load-bearing application is a building regulations violation and a safety risk. C16 has 33 per cent less bending strength than C24. The cost difference is typically only £20 to £40 per cubic metre, which is nothing compared to the cost of a structural failure or a failed building control inspection.
Durability classes and timber treatment
Natural durability is measured by how long the heartwood resists fungal decay when in contact with the ground. The European standard BS EN 350 classifies timber into five durability classes. This is separate from the use class system (BS EN 335) which describes the exposure conditions the timber will face.
Durability classes (BS EN 350)
| Class | Rating | Ground contact lifespan | Example species |
|---|---|---|---|
| 1 | Very durable | 25+ years | Teak, iroko, robinia |
| 2 | Durable | 15-25 years | European oak, sweet chestnut |
| 3 | Moderately durable | 10-15 years | Western red cedar |
| 4 | Slightly durable | 5-10 years | Scots pine, larch, Douglas fir |
| 5 | Not durable | Under 5 years | Spruce, ash, beech, elm |
One critical point: these classes apply to heartwood only. Sapwood from any species is always class 5, regardless of how durable the heartwood is. This is why you will see rot starting at the edges of even oak fence posts if the sapwood was not removed or treated.
Use classes (BS EN 335)
The use class system tells you what level of preservative treatment your timber needs based on where it will be installed:
- UC1 - Internal, no wetting risk. Floors, internal joinery, upper floor joists. No treatment needed for durable species.
- UC2 - Internal, occasional damp risk. Roof trusses, wall framing, bathrooms. Treatment recommended. Lifespan: 15 to 25 years.
- UC3 - External, above ground. Fencing panels, cladding, window frames. Treatment required. Lifespan: 15 to 30 years.
- UC4 - External, ground contact. Fence posts, deck supports, retaining walls. Heavy treatment essential. Lifespan: 25 to 60 years.
No UK softwood survives ground contact untreated
No softwood commercially available in the UK has sufficient natural durability to be used in ground contact without preservative treatment. Even larch and Douglas fir (class 4) will deteriorate within a decade when buried. For fence posts, deck supports, and any timber touching the ground, always specify UC4 pressure-treated timber or use a naturally durable hardwood like oak.
Softwood vs hardwood vs engineered: the full comparison
| Factor | Softwood | Hardwood | Engineered |
|---|---|---|---|
| Cost per m³ | £300-600 | £800-2,000+ | £500-1,200 |
| Strength | C16-C24 (16-24 MPa) | D30-D70 (30-70 MPa) | Variable, up to 40+ MPa |
| Natural durability | Class 4-5 (low) | Class 1-5 (varies) | Depends on species used |
| Max span | Up to 6m typical | Up to 8m (oak) | Up to 30m+ (glulam) |
| Dimensional stability | Moderate shrinkage | Low-moderate | Excellent |
| Workability | Easy to cut and fix | Harder, needs carbide tools | Easy (standard tools) |
| Availability | Widely available | Specialist merchants | Specialist order |
| Sustainability | Fast growing, FSC/PEFC | Slow growing | Efficient material use |
| Best for | Framing, roofing, general construction | Joinery, flooring, oak frames | Long spans, high loads, modern methods |
Best timber for common UK projects
Here is a quick reference for the most common construction scenarios, with budget, mid-range, and premium options for each.
Roof trusses and rafters
C24 graded softwood is the standard. TR26 is required for manufactured trusses. Most roof work uses imported Scandinavian whitewood or redwood. For a typical domestic roof, expect to use 47x100mm or 47x150mm C24 timber for rafters, with battens at 25x50mm treated softwood.
Floor joists
C24 solid softwood for traditional construction, or engineered I-joists (JJI-Joists) for modern timber frame. I-joists span further and bounce less than solid timber at the same depth. For a typical domestic first floor, solid joists are usually 47x200mm or 47x225mm C24.
Stud walls and partitions
C16 is perfectly adequate here since stud walls are not load-bearing in most domestic situations. CLS (Canadian Lumber Standard) timber is the standard choice at 38x89mm finished size. It comes planed and with rounded edges, making it quick to work with.
Decking
Budget: UC4 pressure-treated softwood (around £3 to £5 per metre). Mid: Siberian larch or Western red cedar (£8 to £15 per metre). Premium: Ipe or other tropical hardwoods (£20+ per metre, 40 to 60 year lifespan).
Fencing
Posts: UC4 treated softwood or sweet chestnut heartwood. Panels: UC3 treated softwood. For long-lasting boundaries, sweet chestnut cleft pale fencing is excellent and often locally sourced in southern England at competitive prices.
External cladding
Western red cedar (class 3, no treatment needed, silvers gracefully). Siberian larch (class 3-4, similar performance to cedar). European larch (class 4, cheapest natural option). All develop an attractive grey patina over time if left unfinished. For painted finishes, Accoya (modified softwood) offers class 1 durability.
Typical cost per linear metre by application (2026 UK prices)
Fire safety and building regulations
Fire safety is a critical consideration when specifying timber in UK construction, particularly since the post-Grenfell regulatory changes. Understanding the rules prevents expensive mistakes and delays at building control.
Approved Document B requirements
Approved Document B (Fire Safety) of the Building Regulations for England sets out fire performance requirements. There are two distinct concepts to understand:
- Fire resistance measures how long an assembly prevents fire spread (e.g., a 30-minute fire door, a 60-minute compartment wall). Solid timber performs well here because it chars at a predictable rate of around 0.7mm per minute, maintaining structural integrity.
- Reaction to fire measures how a material contributes to fire development. Untreated timber typically achieves Euroclass D. Fire retardant treatments can improve this to Euroclass B, the highest classification achievable for wood products.
Height restrictions
Since the 2018 ban on combustible materials in external walls of buildings over 18 metres, timber use in taller buildings faces restrictions. In residential buildings over 11 metres, external cladding, balconies, and surfaces must achieve class A1 or A2-s1,d0, effectively prohibiting timber for these elements. Timber structural frames remain permitted inside the building envelope up to 18 metres. New blocks of flats at 11 metres or above must have sprinkler systems.
Timber cladding on residential buildings
Timber cladding is not permitted on residential buildings over 11 metres in height under the amended Approved Document B (effective December 2022 in England). Below 11 metres, timber cladding is permitted but must meet the relevant Euroclass rating for the building type. Always check with building control before specifying timber externally on any project over two storeys.
Where to buy timber in the UK
Where you buy matters as much as what you buy. The quality difference between a dedicated timber merchant and a big-box DIY store is significant.
Dedicated timber merchants
Independent timber yards and specialist merchants like Arnold Laver, Howarth Timber, and EcoChoice typically offer better quality, more species choices, and will cut to length. They can source specific grades and treatments, and most will let you hand-pick pieces from the rack. Prices are often competitive with the chains, especially for bulk orders.
Builders merchants
Travis Perkins, Jewson, Selco, MKM, and Buildbase all carry standard structural softwood (C16 and C24), treated timber, sheet materials, and basic mouldings. Quality varies by branch and supplier. The advantage is convenience and trade accounts. For large structural orders, get a quote from both a builders merchant and a dedicated timber yard.
Online timber suppliers
Companies like Materials Market and Timber DIY offer online ordering with delivery. Useful for comparing prices, but you cannot inspect the timber before purchase. Some offer sample services. Online prices can be lower due to lower overheads, but delivery costs often negate the saving on small orders.
The timber yard advantage
A proper local timber yard will not accept rubbish from their suppliers, while the big chains will put anything on the shelf regardless of quality. If straightness, grain quality, and consistent grading matter to your project, drive to the timber yard. The extra 20 minutes in the van will save you hours sorting through twisted, knotty offcuts at a DIY shed.
Timber construction in action
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Mr Everett's Design and Technology Workshop
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Why Choose Structural Timber For Your Self Build
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A Total Beginner's Guide to Woodworking
Steve Ramsey - Woodworking for Mere Mortals
What tradespeople are saying
Frequently asked questions
Technically yes, but only for very short spans in light domestic situations. Building control and most structural engineers will specify C24 for floor joists because it offers 50 per cent more bending strength and significantly less deflection (bounce). The cost difference is minimal, typically £20 to £40 per cubic metre. Use C24 for all load-bearing floor, roof, and beam applications.
CLS (Canadian Lumber Standard) timber comes planed on all four faces with rounded edges. The finished size for "4x2" CLS is 38x89mm. Regularised timber is only planed on two faces (the wide faces) with sharp edges, and its finished "4x2" size is 44x95mm, which is slightly larger than CLS. CLS is smoother and easier to handle; regularised is more common in traditional construction. Both are acceptable for stud walls.
UC4 pressure-treated softwood typically lasts 25 to 60 years in ground contact, depending on the treatment method and soil conditions. The old copper-chrome-arsenic (CCA) treatment lasted longest but has been banned in the EU since 2004. Modern copper-based treatments (tanalised, MicroPro) are effective but generally do not last quite as long as CCA. For maximum lifespan in ground contact, use oak or sweet chestnut heartwood, which can last 25 years or more without any treatment.
Per cubic metre, engineered timber typically costs more than structural softwood but less than hardwood. However, the comparison is not straightforward. Engineered I-joists often work out cheaper than solid timber joists because they span further at the same depth, reducing the number of joists needed and allowing smaller structural sections. CLT and glulam are more expensive per unit but save on labour costs through faster installation. Compare the total installed cost, not just the material price.
For private domestic projects, certification is not legally required but is strongly recommended. For public sector projects, the UK government procurement policy requires either FSC or PEFC certification (or equivalent) as evidence of legal and sustainable sourcing. Both schemes are accepted equally. If your client cares about sustainability, or if you are working on a commercial or public project, specify FSC or PEFC certified timber. Most major UK merchants stock certified timber as standard.
For non-load-bearing partitions up to 2.4 metres high, 38x63mm or 38x89mm CLS timber is standard. For load-bearing stud walls, you will need at least 38x89mm C16 or C24 (check with your structural engineer). Studs are typically spaced at 400mm or 600mm centres. Moisture content should be below 20 per cent at the time of installation to prevent shrinkage and cracking of plasterboard finishes.
