|Theme:||Sustainable Asset Management
- Flood Defence,
- Sustainable Development,
- technology and innovation,
- environmental management,
- engineering and construction,
A research project commissioned by the Environment Agency on lesser known species of hardwood timber has generated technical data which will allow engineers to use a wider range of timbers for marine and freshwater marine construction, thereby supporting more sustainable forestry on a global scale.
The Environment Agency builds and maintains coastal and freshwater structures throughout England and Wales, many of which incorporate timber. Timber is a renewable resource and an environmentally acceptable choice of construction material if obtained from a recycled source or well managed forests.
Timber has been used for marine and freshwater construction applications for centuries because it exhibits a range of properties that make it particularly suitable for use in these environments, such as:
- high strength to weight ratio
- high density
- good workability
- good durability to attack by decay-causing fungi
- resistance to attack by marine borers (gribble and shipworm)
- ability to withstand shock and impact loads
- resistance to abrasion.
A narrow range of “tried and tested” tropical hardwood timbers are normally used for these applications, with Greenheart and Ekki being the preferred choice in many cases. However, this over-reliance on a few species is not compatible within sustainable forest management in the longer term, as certain species are being over-exploited causing supply issues and price rises.
The main obstacle preventing the wider use of lesser known species is a lack of reliable technical data on their performance. The marine and freshwater construction industry is generally reluctant to use timber species without a proven track record. This is understandable as often the material cost of timber in a construction scheme is dwarfed by the overall construction cost. However, it means that this impasse can only be overcome if reliable data on the performance of lesser known species of timber are obtained. Therefore we commissioned this research project to try to encourage the specification and use of a number of lesser known hardwood timber species, as alternatives to Greenheart and Ekki.
The results of the research will be of interest to anyone who uses timber in marine and freshwater applications, particularly structural and civil engineers, design consultants, building contractors and asset managers.
The results have been brought together in a user guide, containing a step-by-step methodology for identifying the most suitable timber species for different uses, along with tables of technical data on the key properties of a range of lesser known species.
The most comprehensive set of data (e.g. on strength, natural durability, resistance to abrasion and resistance to attack by marine borers) is available for the following five lesser known species:
However the user guide also contains information on thirteen other lesser known species of hardwood timber which can be used in applications where strength is not critical. The performance of the lesser known species is compared with that of Greenheart and Ekki which were chosen as benchmark species.
Although the functional performance of a timber and its ability to withstand the most dominant site-specific hazards or risks should drive the choice of timber species, other factors may also influence the decision making process, such as availability of the timber within project timeframes, cost, required section sizes and workability. Ultimately, the decision about which species to use will depend on a mixture of technical, environmental and commercial considerations.
The results of this research project will help staff to make more informed decisions about the choice of timber they use in marine and freshwater structures, improving their service life. They will ensure that the Environment Agency contributes to the wiser, more sustainable use of natural resources.