This study has been undertaken to investigate the durability of plywood made from non-durable wood (simul, Bombax ceiba) veneer treated by neem (Azadiracta indica, A. Juss.) leaves. The veneers were treated with cold and hot water solution of neem leaves of different concentrations (10%, 5%, 2.5%) and treatment durations (1, 2, 3 days) for cold water and 20, 40 and 60 minutes for hot water. The plywood were made at three different pressures 1.05, 1.40, 1.76 N/mm2 in hot press using urea formaldehyde glue. Durability were investigated with pure cultures of two wood destroying white rot fungi Phanerochaete chrysosporium (Pc) and Ceriporiopsis subvermispora (Cs). After 16 weeks exposure, weight losses of 22.55-20.87 % were obtained in plywood samples treated with 10 % neem leaves in cold water. Weight losses of 29.71-26.92 % were obtained in plywood samples treated with 5% neem leaves- cold water. The plywood samples made of treated veneers with 1:10 (10%) neem leaves in hot water had average weight losses of 22.5-25.5%. In the present study, weight losses of 25.47 and 22.31 % was obtained in plywood samples treated with 10 % neem leaves in hot water. Weight losses of 34.49-30.77 % were obtained in plywood samples treated with 5% neem leaves-hot water. The percentage of weight losses observed in control plywood samples was ranging from 55 to 66. In all the cases, the analysis of variance showed significant difference among the time period & concentration 1:10, 1:20 and 1:40. After mycological test, the treated samples were classified according to British standard BS EN 350-1 (1994a) and 10 % neem leaves treated samples found moderately durable.

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