Question 1

What is glulam?

Accepted Answer

Glulam (glued laminated timber) is an engineered structural timber product made by bonding multiple layers of dimensioned timber boards together with structural waterproof adhesive, with all grain directions running parallel to create a single large structural member. The individual laminations are typically 33-45mm thick; a finished glulam beam may have 5, 10, 20 or more laminations depending on the required depth. By selecting and grading individual laminations, weaker pieces can be placed in lower-stress zones and stronger pieces at the tension face, achieving a more efficient structure than a solid timber section of the same size. Glulam can be manufactured straight (for beams and columns) or in curved forms (for portal frames and arched structures), a unique advantage over solid timber and steel. It is manufactured to BS EN 14080 and supplied in strength grades from GL24h (the most common) to GL32h.

Question 2

What are glulam beams used for?

Accepted Answer

Glulam beams are used for structural applications requiring large spans or large cross-sections that are impractical or uneconomical with solid timber. Common applications include: roof beams in open-plan residential extensions and loft conversions where large clear spans are needed without the visual bulk of a steel beam; exposed ridge beams and purlins in high-quality residential construction where the timber aesthetic is desired; portal frames for commercial, agricultural, and public buildings (schools, leisure centres, churches) where curved or arched structures are architecturally desired; large clear-span roofs for sports halls, supermarkets, and warehouses; and columns in timber frame construction. Glulam can span 10-20 metres or more in standard beam applications, and considerably further in trussed and portal frame configurations. For residential extensions requiring spans of 3-6 metres with exposed beam aesthetics, glulam is a popular alternative to steel RSJs.

Question 3

What are glulam appearance grades?

Accepted Answer

Where glulam will be visible (exposed beams and structural elements), BS EN 14080 defines appearance grades that control the visual quality of the finished product. The main appearance grades used in the UK are: Industrial (lowest visual quality - knots, splits, and surface defects acceptable; for hidden structural use); Standard (some knots and defects permitted; for structural use where appearance is not critical); Architectural (higher quality laminations with limited knots, smooth surfaces, matched joints; for visible use in commercial and public buildings); and Premium (the highest grade - clean, matched laminations, no visible defects; for prestige residential and feature applications). Appearance grade is separate from structural grade - a Premium appearance glulam is not necessarily stronger than an Industrial grade, though in practice higher visual grades often use higher quality timber that also performs better structurally.

Question 4

How does glulam compare to steel and solid timber?

Accepted Answer

Glulam versus solid timber: glulam achieves much larger sections and spans than solid timber, uses smaller input pieces (addressing the shortage of large-section structural timber), has more consistent structural properties (defects are distributed across laminations rather than concentrated), and can be manufactured in curved forms. It is significantly more expensive than equivalent solid timber sections. Glulam versus steel: glulam has a lower carbon footprint than steel (timber is a carbon-sequestering material; steel production is highly carbon-intensive), achieves competitive strength-to-weight ratios, offers natural aesthetics without cladding or fire protection (for lower exposure categories), and can achieve curved forms that are expensive to fabricate in steel. Steel has higher strength and stiffness per unit cross-section, does not absorb moisture, and is often easier for builders to connect to and support. For most residential extension beam applications, a glulam beam will be larger in section than an equivalent steel RSJ for the same span - but that may be architecturally desirable.

Glulam

Just so you know...