Glulam & LVL: Engineered Timber Beams Explained

Glulam (glued laminated timber) and LVL (laminated veneer lumber) are the two dominant engineered timber beam products used in UK structural work. Both outperform solid timber in strength, dimensional stability and predictability, yet they suit different applications. Understanding how they differ helps you specify confidently for extensions, loft conversions, open-plan remodels and new-build frames.

Glulam is made by bonding multiple kiln-dried sawn timber laminations face-to-face, and BS EN 14080 covers glulam made from laminations 6 mm to 45 mm thick.¹ LVL is manufactured by stacking thin rotary-peeled wood veneers (typically about 3 mm thick) with the grain running largely parallel, then pressing and bonding them under heat.² The result in both cases is a product that carries structural loads far more efficiently than a single sawn section of equivalent size, with far less risk of warping, splitting or shrinkage.

Glulam vs LVL vs Solid Timber

Solid C24 sawn timber is the cheapest option but is limited to modest spans (typically ≤4.8 m for domestic floor joists) and is prone to moisture movement.³ Glulam and LVL both eliminate most of the natural variability that limits sawn sections.

For scale, one builders’ merchant lists 47 × 200 mm C24 carcassing at £19.68 excluding VAT for a 3.0 m length, which works out at about £700 per cubic metre.⁴

Glulam is typically preferred where appearance matters, exposed ridge beams, open-plan structural posts, or visible roof structures. LVL is more common in concealed positions: hidden behind plasterboard, within flat roof build-ups, or as the flanges of I-joists.

Strengths and Grades

Glulam is graded by strength class under BS EN 14080:2013, the glulam product standard, which BSI published in the UK on 31 January 2014.¹ The most common UK grades are:

• GL24h / GL24c, economical grade; appropriate for most domestic applications
• GL28h / GL28c, higher strength, used where spans or loads exceed GL24 capability
• GL32h / GL32c, less common, typically specified for commercial or industrial work

The suffix ‘h’ denotes homogeneous lamination (all laminates the same grade); ‘c’ denotes combined lamination (stronger outer laminates, lower-grade core).⁵ Binderholz’s published data to BS EN 14080 gives GL28h a mean modulus of elasticity of 12,600 N/mm², against 12,500 N/mm² for GL28c.⁵ For most residential UK projects, GL24h or GL28h is sufficient.

LVL products are not formally graded in the same letter-number system. Manufacturers publish characteristic strength values directly: Metsä Wood’s Kerto-S, a widely used softwood LVL, is rated at 44 N/mm² in edgewise bending and 50 N/mm² flatwise, with a mean modulus of elasticity of 13,800 N/mm².⁶ Always use manufacturer-specific design data, as properties vary between brands. LVL is typically designed to BS EN 14374:2004 and used in Eurocode 5 (BS EN 1995-1-1) timber design.⁶

Spans

Engineered timber beams can achieve spans that would require steel in an equivalent solid timber section. Typical domestic scenarios (indicative only, always get a structural engineer to confirm):

LVL with its higher strength often allows a shallower depth for the same span, a meaningful advantage where floor-to-ceiling height is constrained. For equivalent loads LVL can be somewhat shallower than glulam, although where deflection governs the gain is smaller, because the two materials are closer in stiffness than in strength.

Spans are governed by both bending and deflection, and deflection is usually the one that decides the section. The deflection limits a designer works to come from Eurocode 5 and its UK National Annex, not from Approved Document A: Part A sets no numerical deflection limit and tabulates no timber spans at all, pointing a reader to the TRADA span tables instead.⁷ Both products are designed under Eurocode 5 (BS EN 1995-1-1) with the UK National Annex.

Appearance

Glulam is architecturally attractive, the lamination lines are visible but create a controlled, regular aesthetic that reads as deliberate rather than structural compromise. Grades with finger-jointed laminates visible on side faces can be specified as an architectural finish. Natural oils, hardwax oils or clear lacquers are typical finishes.

LVL has a fine-grained veneer surface that is less visually interesting. It tends to be used concealed or clad in softwood trim where it is exposed. It should not be confused with CLT (cross-laminated timber), which has its own structural behaviour and visual language.

Cost vs Steel

For spans up to roughly 6–7 m, glulam is often cost-competitive with steel, and sometimes cheaper once you account for fire protection. Under Building Regs Part B, the loadbearing structure of a house of up to three storeys generally needs at least 30 minutes’ fire resistance, which an exposed steel beam usually reaches only with intumescent paint or board encasement.⁸ Glulam chars at a predictable rate, about 0.7 mm a minute in Binderholz’s published data, so a large enough section can reach the same period with no additional protection.⁵

For spans beyond 8–9 m in domestic work, steel becomes harder to beat on price and headroom. Very long glulam members are also harder to manoeuvre on restricted sites.

A rough comparison for a 5.5 m clear span, medium load:

Note these are rough order-of-magnitude figures. Actual costs vary by contractor, region, and structural complexity.

Where Glulam and LVL Are Used

Glulam suits:

• Exposed ridge beams and purlins in vaulted ceilings
• Open-plan ground-floor beams replacing load-bearing walls
• Portal frame structures in agricultural buildings or extensions
• Structural posts in timber frame construction
• Loft conversion hip-to-gable beams

LVL suits:

• Hidden floor and roof beams where section depth is critical
• Structural door and window headers concealed in wall builds
• Flanges and chord members in prefabricated engineered floor systems
• Flat roof structural build-ups

Building Regulations and Standards

Both products fall under Part A (Structure) of the Building Regulations in England. A structural engineer must size the beam for your specific loads and span. Their calculations will reference:

• BS EN 1995-1-1 (Eurocode 5), timber structures design standard
• BS EN 14080:2013, glulam product standard¹
• BS EN 14374:2004, LVL product standard⁹
• UK National Annex to Eurocode 5, UK-specific design parameters

For fire, both are assessed under BS EN 1995-1-2 (fire design of timber structures). Where exposed, specify the charring rate and reduced cross-section method with your structural engineer.¹⁰

Both glulam and LVL should be supplied with a Declaration of Performance and UKCA or CE marking confirming the structural class; the government has confirmed that the CE mark remains available for construction products placed on the market in Great Britain.¹¹ Ask your supplier for the product’s characteristic values before design begins.