Potentially momentous times for tropical timber22 November 2018
There are major opportunities for tropical timber in marine civil engineering applications, but only if suppliers and customers are persuaded to use a wider range of lesser-known species, writes Dr John Williams, principal consultant at engineering, environmental and technical services consultancy RSK
I’ve been a peripatetic timber consultant working in all sectors of the construction industry for over 20 years. I’m intrigued by the perennial problem of convincing industry to use a wider range of lesser-known timber species (LKTS). This is especially so for marine civil engineering.
There are over 880,000 properties in the UK within 100m of mean high water, with at least 50,000 protected by groyned beaches. Timber groynes form a significant element of this coastal protection and traditionally we’ve used greenheart and, more recently, ekki for the purpose. So, what’s the problem?
Okay, so the environmental and socio-economic arguments for timber are well known. It’s a renewable resource, but that does not mean it’s inexhaustible. Demand for greenheart and ekki for coastal engineering puts pressure on these species. Therefore, it is desirable to use a wider range of LKTS.
Timber costs are often dwarfed by construction costs, meaning timber has to deliver a long service life. Consequently, this sector is conservative and reluctant to specify LKTS without a proven track record.
Furthermore, fear of the unknown has created the tendency to default to greenheart and ekki, resulting in over-reliance on these species. Their track record fuels conservatism and this is exacerbated by a dearth of reliable technical information indicating service life performance, deterioration rates and, most importantly, strength of LKTS.
The good news here is growing activity to raise awareness of LKTS, which will relieve pressure on ekki and greenheart and there are established fast track test methods to benchmark marine performance.
But the bad news is that the principal hurdle yet to be overcome is determining timber strength class. The potential risk of structural failure prevent specification of LKTS without a D value and establishing this requires significant investment, which, to date, has been prohibitive. Moreover, accepted test methods may not be appropriate for timber destined for groynes, begging the question, can streamlined, focused testing deliver reliable strength values for LKTS?
Whatever the answer, one certainty is suppliers and importers must support LKTS with reliable performance data, especially strength, to stand a decent chance of successful market development. No data, no market, end of discussion. So there is a need for significant R&D funding from suppliers and collaboration with end users to define performance data. This is more acute than ever because tropical timber faces growing competition from alternative materials, such as recycled polymers and a move towards rock armour schemes. But it is not just incumbent upon suppliers to invest in R&D. End users must build on the initial foundations laid by suppliers by specifying LKTS and investing in long-term performance evaluation to build confidence.
Specifying LKTS, fit for purpose, will relieve pressure on ekki and greenheart. This will lead to a more diverse timber trade which, inevitably, tilts the balance in favour of sustainable forestry.
Typically, tropical hardwood groynes should provide a minimum service life of 25 years. The best time to have tested LKTS was 25 years ago. The next best time to test them is now.