AS 1720 | Chalkline

AS 1720 is the Australian Standard series for timber structures. Engineers use it for member design, joint capacities, and engineered timber products. It sits behind AS 1684 (the residential timber framing standard) as the underlying design code: AS 1684 publishes prescriptive span tables derived from AS 1720, and engineers design directly to AS 1720 when AS 1684 doesn’t reach (long spans, high loads, non-standard configurations, engineered products).

The main parts of the AS 1720 series:

AS 1720.1-2010, Design methods: the design code. Member capacities, characteristic strengths and stiffnesses for each stress grade, joint capacity equations, fastening design, durability. The part most engineers reference daily.
AS 1720.2, Timber properties: characteristic values for specific timber species and stress grades.
AS 1720.3, Design criteria for timber-framed pole houses.
AS 1720.4, Fire resistance of structural timber members: charring rates and residual section calculations for fire-resistance compliance.
AS 1720.5, Nail-plated timber roof trusses: design rules for the prefabricated trusses used in most modern roofs.

AS 1720.1 underpins residential timber design even when the builder never reads it. The span tables in AS 1684, the joint group classifications on hardwood structural timber, and the manufacturer’s certified LVL and glulam capacities all trace back to AS 1720.1 equations.

On a residential job, the chippy and builder normally work from AS 1684 span tables or the manufacturer’s engineered timber data; the engineer signs off the AS 1720 calculation when a span, load case, or fastening sits outside those prescriptive tables.

Also known as: AS 1720 series, timber design standard.

Category: Standards / structural timber / engineering.

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