The UK construction sector is being encouraged to increase its use of homegrown timber, as industry experts highlight the benefits of locally sourced materials over imports. Despite the availability of sustainable domestic options, nearly 80% of timber used in the United Kingdom continues to be imported. This reliance is now being questioned across the supply chain. Timber merchants, sawmillers, manufacturers and contractors are recognising the advantages of British-grown timber. These include lower carbon emissions, reduced costs and improved supply chain security.
There is growing awareness. Local timber offers practical benefits. Demand for sustainable materials is also rising. Customers are increasingly prioritising environmentally responsible construction products. This shift is influencing procurement decisions.
A key issue raised within the sector relates to timber grading. Architects and engineers frequently specify higher grades such as GL28 or C24 without fully assessing project requirements. This trend has developed due to historical dependence on imported Scandinavian timber, where C24 is the standard grade. In contrast, the most common grade produced in the UK is closer to C16.
This mismatch has led to inefficiencies. British timber is often overlooked. Specifications are sometimes made without full evaluation. The ‘Trust UK C16’ campaign is aiming to address this imbalance. It promotes confidence in locally produced timber grades that are suitable for many applications.
Industry specialists emphasise that understanding timber grades is essential. It is not just about numerical values. It involves balancing structural performance, cost and sustainability. In many cases, lower grades can meet design requirements effectively. Greater flexibility exists than is often assumed.
When glulam is specified, two main factors are considered. These are structural strength and deflection. Strength ensures that loads can be carried safely. Deflection determines how much a beam will bend under load. In practice, deflection often governs design decisions.
This distinction is important. Small increases in beam depth can significantly improve stiffness. The relationship between depth and stiffness is exponential. As a result, slightly deeper beams made from lower-grade timber can perform similarly to higher-grade alternatives.
Glulam grading follows a clear system. Grades such as GL20, GL24 and GL28 indicate bending strength. Higher numbers represent stronger materials. Additional letters describe construction methods. Homogeneous beams use the same grade throughout, while combined beams use stronger timber in high-stress zones.
Efficient material use is encouraged. Combined construction is often preferred for higher grades. This approach reduces waste and improves cost efficiency. It also aligns with manufacturing practices.
Availability varies by species. Spruce remains the most widely used material for glulam. UK-grown spruce typically achieves GL20h. Imported spruce is commonly available as GL24h, with higher grades also accessible. However, these higher grades are less frequently required in practice.
Larch and Douglas fir follow similar patterns. UK-grown material is generally produced at GL20h. Imported options can reach GL24h or GL28c, although availability is more limited. Oak glulam is treated differently. It cannot currently be graded under Eurocode standards and is usually assigned a conservative GL24 rating.
Pine is also used. It is most commonly specified as GL24h. Higher grades are less common due to limited usage in glulam production.
The impact of grade on beam size is often overestimated. In many cases, only minor increases in depth are required when using lower-grade timber. For example, a beam specified at 440 mm in GL24 may only need to increase to 460 mm in GL20. These differences are relatively small.
Real-world projects have demonstrated this principle. At the Horniman Museum project, locally sourced timber was successfully used without increasing beam sizes. Design adjustments allowed for the use of British-grown materials while maintaining performance standards.
The relationship between solid timber grading and glulam grading is also significant. C16 timber, commonly produced in the UK, can be laminated to create GL20 beams. The lamination process enhances strength by distributing loads and reducing the impact of defects.
At higher grades, bonding becomes more critical. The strength of glue lines and joints can limit performance. This means that beyond certain thresholds, material quality alone is not the determining factor.
Experts stress that a single grade does not need to be used across an entire project. Strategic sourcing is being recommended. Different materials can be selected for different applications. This approach improves efficiency and sustainability.
Transport emissions are a key concern. Locally manufactured timber significantly reduces carbon impact. Large structural elements can be produced closer to site. This reduces haulage distances and associated emissions.
Visual quality is not compromised. The appearance of glulam is determined by visual grading rather than strength classification. High-quality finishes can be achieved with lower-grade timber.
Projects such as the Lobslack Seed Processing Facility for Forestry England have demonstrated the benefits of mixed sourcing. British-grown larch, locally manufactured beams and imported components were combined effectively. The outcome was cost-efficient and environmentally responsible.
Early engagement is critical. Designers are encouraged to involve timber suppliers at the initial stages. This allows for better decision-making and avoids costly revisions. Specifications can then be optimised for performance, availability and sustainability.
Organisations such as Grown in Britain are supporting this transition. The certification scheme promotes responsible forest management and supply chain transparency. In 2025, it achieved Category A status under the UK Government’s Timber Procurement Policy. This development has removed barriers to using certified homegrown timber in public projects.
The UK timber industry is evolving. Greater emphasis is being placed on local sourcing. Sustainable construction practices are gaining momentum. Homegrown timber is expected to play a larger role in future developments.
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