HEADE Rtech note 1

Technical notes

Developed in collaboration with Timber Design Society.

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Providing solutions through collaboration

In a joint effort to advance timber structure design and encourage greater utilisation of timber in construction, Timber Unlimited and the Timber Design Society (TDS) have partnered to enable quicker and broader access to essential New Zealand-focussed Technical Notes. By breaking down barriers and demystifying timber's use in structural design, these Technical Notes (available below) delve into and clarify specific design topics crucial for achieving excellence in robust timber design.

If you are actively involved in timber design and would like to get access to TDS membership and its associated benefits, visit the website here.

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Dr Daniel Moroder, Technical Manager, PTL | Structural & Fire
Dr Andy Buchanan, Principal, PTL | Structural & Fire

For timber, the classical meaning of density as the “mass of a substance per unit volume”, requires some clarification, as the term is used in different ways depending on the trade and the context. As timber is also a hygroscopic material, any density value is affected by the moisture content at the time of measurement.

Timber density is not only relevant for determining self-weight. It is often used to characterise wood quality in forestry, it is used to determine fastener strength when designing structures, and it is also used to describe the charring rate of timber members in fires. This technical note summarises the various definitions of density used both in forestry and timber engineering and relates these to the commonly used timber design standards used in New Zealand, Australia and Europe.

Fire Supplement Tile Webtech note 1


Dr Tobias Smith and Dr Daniel Moroder
PTL | Structural & Fire, Christchurch 

Timber is an anisotropic material, and accordingly, its mechanical and physical properties are direction-dependent. This means its ability to resist loads and deformations parallel to the grain differs from that perpendicular to the grain. In many design situations, timber members are subject to bearing loads being applied perpendicular to the grain. This technical note describes what is bearing perpendicular to the grain, how it was derived in NZS AS 1720.1:2022, how it relates to similar European verifications and how the value should be used in design.

Fire Supplement Tile Webtech note 12


Dr Tobias Smith
PTL | Structural & Fire, Christchurch 

NZS AS 1720.1:2022 introduced a new Chapter (ZZ9), which sets out the minimum seismic design requirements for timber structures design.  This new chapter introduces two new terms viz., Potentially Ductile Elements (PDEs) and Capacity Protected Elements (CPEs). Separating the PDEs and CPEs is the overstrength of the PDE. This technical note discusses overstrength and its use in NZS AS1720.1:2022. It also discusses the limitation placed on overstrength actions by the Standard and how this is applied.