The story behind world-leading technical guides

The story behind the transition from guesswork and tradition to scientific modelling in the WoodSolutions Timber Service Life Design Guide.

WoodSolutions Technical Design Guide - Timber Service Life Design cover

For many years the estimation of timber service life was a combination of experience, extrapolation and guesswork. The result of more than 10 years work, the WoodSolutions Timber Service Life Design Guide and TimberLife Educational Software, are world-leading resources that challenge that paradigm to provide designers and specifiers with accurate, evidence based information. Both are available for free download from

Coming from a technical and scientific background with the CSIRO, timber engineer Colin Mackenzie could see room for improvement in the way designers, specifiers and builders forecast timber durability and selected their timber components.

“It was all, ‘This is the way we’ve always done it,’ or “I know how long this will last, I’ve seen it done like this’ or even ‘This should be OK, looks about right,’ that’s the way a lot of the industry operated’” Colin said.

“Working with Timber Queensland in an advisory role including developing timber use and application guides and codes and standards, it was a natural thing to get involved with compiling a publication like the Timber Service Life Design Guide.

Colin went on to explain that the whole process involved a team of about ten people with diverse backgrounds ranging from wood pathology, engineering and risk management to metallurgy, and around a decade of ongoing work.

“We knew at the outset that this wasn’t going to be easy,” he said, “the final publication is based on a wide range of individual studies, most of which had to apply for independent funding, the whole process moved forwards in steps and stages as funds and information became available.

“It was also a massive exercise in turning a vast amount of performance data into something that’s actually practical and usable for architects, building designers, engineers and the like. There’s no point in handing over the mathematical models behind the results, they are just too complicated for a non-specialist.

WoodSolutions Technical Design Guide - Timber Service Life Design flow chart

Decision making flow charts present information logically and usefully

“At one stage I had all the documents relating to the Guide in archive boxes, I reckon there was a tower nearly 500mm high of A4 papers on my office floor!

The success of the team’s translation of the raw data is evident in the apparent simplicity and usability of the design guide. Service life expectations are clearly defined according to the location, application and nature, that is species and treatments, of the timber in use.

Selecting the most appropriate timber for an application, or determining the expected service life and even anticipated maintenance is a relatively simple process of following a flow chart.

“However, we were aware that there would be circumstances that we couldn’t cover off completely in the Guide,” said Colin, “That’s where the Timber Life Education Software comes in. It essentially uses some of the mathematical models behind the data in the guide, allowing users to input their own variables and see the results that apply to their own situation.

Colin went on to explain that the TimberLife software had been used by organisations like electricity utilities to plan programmed maintenance and replacement schedules for wooden power transmission poles.

“It’s been a very satisfying exercise.” Colin concluded, “In the Timber Service Life Design Guide, last revised in October 2013, we now have a resource that enables specifiers to use timber in the correct and proper manner to satisfy all applicable codes and standards.

“If your target design life is 5 years, 15 years or 50 years, which are the implicit target building performances of the Building Code of Australia, and you have a specific application for timber in region X, Y or Z then the Design Guide will give you the timber species and/or preservative treatments that satisfy the minimum requirements for achieving those service lives.

WoodSolutions Technical Design Guide - Timber Service Life Design geographic zones

Location is a factor in durability, zones determine the rating of different species

“The Guide is there to provide more reliable prediction of timber service life for any species in any application, anywhere in the country,” Colin concluded, “in fact the processes behind the Guide have now been adopted in the US and EU markets, so you could probably say we lead the world.

The WoodSolutions Timber Service Life Design Guide of approximately 100 A4 pages is available in pdf form from, or it is available as hard copy for purchase from The TimberLife software is available for free download from WoodSolutions. Please note that it is PC only.

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