The dimensional stability such as thickness swelling and water absorption of plywood made of treated simul (Bombax ceiba) veneers were investigated after 2 hours and 24 hours soaking under water. The veneers were treated with hot water and cold water solution of borax-boric acid (1:1), neem leaves and mahogany seeds of different concentration (1:10, 1:20, and 1:40) at different treatment duration. It was observed that the values of swelling were increased with the increase of soaking time from 2 hours to 24 hours. In the case of plywood made of borax-boric acid treated veneers, the percentage of swelling were increased with the increase of borax-boric acid concentration. The values of thickness swelling were also increased with the increase of treatment duration from 20 minutes to 60 minutes and 1 to 3 days. The values of swelling obtained in plywood made of neem leaves and mahogany seeds treated veneers were higher than that of borax-boric acid treated veneers and near to the untreated samples. The mean values of percentage of water absorption in plywood after 2hrs and 24 hours water soaking were determined. It was found that after 24 hours soaking, plywood made of mahogany seeds treated veneers absorbed more water than that of neem leaves treated veneers. All the values obtained from treated samples after 2 hours and 24 hours soaking were lower than the control samples. But it was observed that higher amount of water was absorbed in neem leaves and mahogany seeds treated board in comparison with borax-boric acid treated board. It was also noted that the values of water absorption in leaves and seeds treated board were near the values of untreated samples.

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