TIMBER RESOURCES FOR CONSTRUCTION AND WOODEN PRODUCTS SECTOR IN SRI LANKA
Traditionally construction and wooden products sector select naturally growntimber for most of their timber requirements. These include high rated rarehardwood timber species such as mee, satin, wewarana, milia, palu, halmilla,hulanhik, etathimbiri, dun, alubo, liyan and suriyamara. These species are mostlygrown in natural forests and their supplies have now become very limited. Hencetimber industry has to rely on alternative timber species that originate fromsources other than natural forests. Properties that are essential for the introductionof plantation and home gardens species to the market are discussed in this paper.
Based on density and strength properties, Eucalyptus grandis, E. microcorys,ginisapu, teak, mahogany and jak are potential construction timbers for the future.Teak is an excellent durable timber however it is very expensive. Mahogany is agood timber for door and window frames and sashes but sapwood of this speciesis susceptible for powder-post beetle and termite attack. Jak is a durabletraditional species but felling and usage of this species has been controlled.Eucalyptus is also a durable timber that can be used in construction. Out of twoEucalyptus species E. microcorys is a better timber in terms of its higher densityand resistance to splitting compared with E. grandis.
Wooden products sector includes furniture and export oriented wooden productssuch as toys and wooden components. Albizia, alstonia, lunumidella, pine, rubberand mahogany are some of the potential timbers that can be used in manufacturingthese products. Albizia and lunumidella are used in the manufacture of woodenpanels. However most of these species are not durable, hence they should be usedin interior environments not exposed to water.
It is essential to treat non-durable timbers with preservative chemicals before use.For heavy construction and for exterior applications they should be treated bypressure impregnation mehods using CCA (Copper chorme arsenate). For interiorwooden products boron treatment would be adequate. However, results indicatedthat vacuum pressure impregnation method or low cost hot and cold open tankmethod are more successful in treatment of boron compounds compared withcommonly used diffusion methods. Results show low density species such asalbizia, lunumidella, pine, alstonia and rubber can be easily treated with diffusionmethods. However treatability of heavy density timbers such as E. grandis and E.microcorys are low. It is also essential to season these timbers properly beforebeing used.
While our short term timber requirements are satisfied with imported species suchas kempus, tualang and balau, it is essential to plan for the local fast growing treespecies discussed in this paper to supply the required timber essential for theconstruction and wooden products sector