Glulam beams in Australian construction: GL grades, curved sections, and exposed feature beams

TL;DR

Glulam (glued-laminated timber, GLT) is the structural timber product that fills the gap between sawn solid timber (limited to the size of the tree the log came from) and LVL beams (constant-rectangular sections optimised for hidden structural use): a glulam beam can be straight or curved, made from softwood (Radiata Pine) or hardwood, and is the practical choice when the beam is also a feature visible in the finished space. The Australian standard is AS/NZS 1328 (the manufacturing standard) cross-referenced from Section 7 of AS 1720.1 (the design code). Glulam is used the same way across Class 1a houses, Class 2 low-rise apartments, and Class 3-9 commercial timber framing (post-and-beam, cathedral ceilings, long-span feature beams). Common stress grades are GL8 and GL10 (light loads), GL12 and GL13 (standard structural), and GL17 (heavy or feature beams). Major Australian manufacturers belong to the Glued Laminated Timber Association of Australia (GLTAA) and publish unified span tables. The two specification calls: appearance grade (industrial vs select vs feature, which drives cost more than structural choice) and species/treatment (Radiata Pine for protected interior, hardwood or H3-treated softwood for exposed exterior).

What it is

A glulam beam is a structural timber section built up from layers of solid graded timber (called lamellae, typically 35 to 45 mm thick each) bonded together with structural adhesive, all lamellae with grain parallel to the beam’s length. The lamellae are graded individually before glue-up, and stronger lamellae are placed in the outer tension and compression zones where they carry the highest stress; weaker lamellae sit in the neutral-axis middle. This grading-and-placement is what gives glulam its consistent published strength: every beam of a given GL grade behaves the same under load.

The key differences from neighbouring products:

Product	Construction	Where used
Sawn solid timber (Radiata Pine, hardwood)	Cut from a single log	Wall framing, joists, lintels up to the tree’s natural size
Glulam (GLT)	Solid lamellae 35-45 mm thick, glued parallel-grain	Long-span beams, curved beams, exposed feature beams, post-and-beam
LVL	Rotary-peeled veneers ~3 mm thick, glued parallel-grain	Hidden structural beams, lintels, I-joist flanges
CLT (cross-laminated timber)	Solid lamellae glued with grain alternating between layers	Wall and floor panels, mass-timber construction

Glulam can be made curved (segmental glue-up with lamellae bent to a former before cure), tapered, and in non-rectangular cross-sections, which neither LVL nor sawn timber accommodate.

The GL stress grade system

AS/NZS 1328 sets out the GL grade system, and AS 1720.1 Section 7 sets the design properties for each grade. The grade label gives the characteristic bending stress in MPa, indexed to a standard 300 mm deep beam.

Grade	Characteristic bending stress (f’b, MPa, 300 mm deep)	Typical application
GL8	19	Light-duty beams, pergolas, fascia structures
GL10	22	Common structural beam (lintels, ridge beams in cathedral ceilings)
GL12	25	Standard structural beam, heavier loads or longer spans
GL13	27	Standard hardwood glulam grade in some manufacturers’ ranges
GL17	36	Heavy structural and feature beams; Tilling SmartLam GL17 is a common high-strength product

Note that GL grades are independent of species: a GL17 hardwood beam and a GL17 softwood beam have the same published bending strength, but the lamellae composition (and the resulting cost, weight, and visual character) differ.

The Glued Laminated Timber Association of Australia (GLTAA) publishes unified span tables that work across member manufacturers, so a span-table reading is portable between Hyne, Wesbeam, Dindas, and Tilling-supplied beams of the same grade and section (verified 2026-05-13 via Hyne glulam product page).

Appearance grades

Glulam carries three appearance grades that determine what the beam looks like in the finished space. None affects structural capacity; they affect cost materially.

Appearance grade	What you get	Where used
Industrial	Visible glue lines, lamellae knots and natural defects, no fill or sand	Beams that will be boxed in by plasterboard or cladding; cheapest
Select	Sanded faces, small defects filled, even glue lines	Visible beams in domestic interiors where some natural character is acceptable
Feature / Architectural	Premium select, knot fill, fine sanding, ready to finish	Cathedral ceiling beams, exposed post-and-beam, polished or stained beams in living spaces

Selecting Industrial when the beam will be exposed is the most common ordering mistake: the price saving up-front is consumed twice over by the painter or finisher who has to fill, sand, and prime knots and glue lines that should have been done at the factory.

Where glulam is the right call

Cathedral ceiling ridge beams: spans of 5 to 8 m through an open living area where the ridge is visible. Glulam in Select or Feature grade, often hardwood, finished with clear or pigmented stain.

Curved beams: arched lintels, curved fascia structures, vaulted ceiling ribs. Only glulam can be made curved at building scale; LVL and sawn timber cannot.

Post-and-beam construction: alpine A-frame, contemporary architectural homes with visible structural timber. Glulam posts (typically 175 to 245 mm square) and beams form the visible structure; non-structural infill closes the envelope.

Long-span pergola and verandah beams: 4 to 6 m spans where the beam is visible and the appearance matters. H3-treated softwood glulam (Radiata Pine, sometimes with end-grain sealer) is the standard pergola choice.

Lintels in feature openings: stone and timber-clad architectural openings where a visible lintel forms part of the design.

Where glulam is wrong

Routine hidden lintels and ridge beams: LVL is cheaper at the same load capacity. Use LVL for any structural member that won’t be visible.
Unprotected exterior weather: untreated softwood glulam absorbs water at the glue lines and the lamellae ends. Use H3-treated softwood glulam, hardwood glulam, or apply a maintained exterior finish.
Direct in-ground contact: even H4 treatment is borderline for in-ground glulam; the glue lines are a moisture trap. Use solid hardwood post or steel base detail.
Fire-rated assemblies (Class 2 separating walls, FRL-rated penetrations): glulam chars predictably but Class 2 and above require tested assemblies and engineer-detailed fire collars at penetrations.
Spans the manufacturer’s table won’t reach: same rule as LVL. Move up in grade, depth, or hand to an engineer.

Sizing and span tables

Two valid paths, same logic as LVL:

GLTAA-unified manufacturer span tables: standard cases (single-span ridge beams, simple-supported lintels, pergola beams) covered by the published GL-grade tables. Read the table for the load condition, span, and grade.
Structural engineer’s design under AS 1720.1 Section 7: required for unusual geometry, multi-load conditions, curved beams (always engineer-specified), cantilevers, or any span outside the table.

Curved glulam is always an engineered detail. The curvature radius limits the lamellae stress: too tight a radius and the outer lamellae fail in tension at glue-up. Confirm the minimum radius with the manufacturer (typically 6 to 12 m for 35 mm lamellae, less for thinner lamellae).

Connections

Glulam connects to surrounding framing via similar fixings to LVL, with two species-specific notes:

Bolts through softwood glulam: standard machine bolts with washers both faces, AS 1720.1 edge and end distances. Tightening must avoid crushing the surface of softer Radiata Pine.
Bolts through hardwood glulam: pre-drill to avoid splitting; some species need oversize holes to allow expansion.
Joist hangers and saddle brackets: for visible beams, custom brackets or hidden connections are often specified to avoid the visual disruption of a hanger. Lead time is the main constraint.
Post bases: glulam posts in exposed positions use galvanised or stainless steel post bases that lift the timber above splash and water-pooling zones. The HoldDown HD or equivalent is standard.

Common defects and on-site issues

Wrong appearance grade for application: ordering Industrial and asking the painter to upgrade it on site is futile. Specify the appearance grade at the start.
Bowed or twisted beam at delivery: glulam is stable but not immune to drying shrinkage if delivered above the project’s equilibrium moisture content. Reject beams with visible twist over the length; stable storage for 2 weeks at the project’s expected moisture content before fixing is standard practice.
Glue line spalling at exposed cut ends: cut ends on exterior beams need end-grain sealer applied immediately. Sealer applied a week later, after moisture has entered the cut, is too late.
Visible glue bleed on Feature grade: a manufacturing defect; the beam should have been rejected at the factory. Returns are valid for any Feature-grade beam with visible glue squeeze-out.
Damaged surface from rough handling: glulam surfaces dent more easily than LVL or hardwood; protect with edge guards and clean dunnage during handling.
Field-cutting a glulam beam to length: the cut must be square to avoid asymmetric load transfer through the bearing; use a track saw or a workshop drop saw, not a hand-held circular saw.

Pricing (2026 indicative, ex-GST, ex-Sydney metro yard)

Section (mm)	Grade	Per linear metre
65 × 200 GL10 (softwood, Industrial)	GL10	$40-60
65 × 300 GL10 (softwood, Select)	GL10	$75-105
85 × 300 GL12 (softwood, Select)	GL12	$110-150
130 × 360 GL12 (softwood, Feature)	GL12	$230-300
65 × 300 GL13 hardwood (Select)	GL13	$180-260
130 × 400 GL17 (softwood, Select)	GL17	$280-380
Curved beam, custom radius and section	Engineer-specified	Premium 40-100% over straight beam
H3 treatment premium	(any softwood section)	+$10-20 per LM

Hardwood glulam (Tasmanian Oak, Vic Ash, Spotted Gum) is typically 2 to 3 times the softwood price at equivalent section, plus the lead time is materially longer (4 to 12 weeks for non-stock sections).

Standards and references

Standards Australia, AS/NZS 1328 Glued laminated structural timber. https://store.standards.org.au (verified 2026-05-13).
Standards Australia, AS 1720.1:2010 Timber structures Part 1: Design methods (Section 7 Glulam). https://store.standards.org.au/product/as-1720-1-2010 (verified 2026-05-13).
Hyne Timber, Glue Laminated product range. https://www.hyne.com.au/glue-laminated (verified 2026-05-13).
Tilling, SmartLam GL17 product page. https://www.tilling.com.au/product/smartlam-gl17/ (verified 2026-05-13).
Australian Building Codes Board, NCC 2022 ABCB Housing Provisions (timber structural references). https://ncc.abcb.gov.au/editions/ncc-2022/adopted/housing-provisions (verified 2026-05-13).