Researches revealed new treatment grades, treatment groups, grading groups, natural durability grades, strength groups and a new preservative combination for remedial treatment and sterilization of most common timbers and bamboos of Bangladesh. The obtained findings are applicable for equivalent timber species having equivalent climatic condition. Sapwoods are always perishable and timbers with whitish to grayish heartwood without tylosis are found to be nondurable and permeable to preservative treatment, recommended to use after preservative treatment following appropriate treatment group. Perishable to durable impermeable heartwoods can be penetrated with boron, suitable for indoor use only. CCA-C is suitable and preferable preservative for ground and water contact use rather than CCB and pentachlorophenol as the laters are leachable. Decay pattern study revealed that the service life of round timber for ground contact use is increased with the increase of adequately CCA-C impregnated (w/w 4% or 20 kg/m3 dry oxides of CCA-C) shell thickness, the preferable shell thickness shall be at least equivalent to 44% of radius (carry 90% of bending load) where remaining untreated central core is not naturally very durable. Kiln-drying with heat sterilization schedule is a key step for adequate treatment and slow drying or accelerated fixation is the post treatment effective step for higher service life.

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