A novel method of improving the water and leaching resistances and durability of a fire retardant-treated wood product by using a chemical fire retardant composition in which crosslinking polyvinyl acetate (XPAVc or X-PVAc) is applied as a protective coating on wood over the fire retardant layer. An additional crosslinking polyvinyl acetate coating layer or one or more layers of acrylic, alkyd, epoxy, lacquer, polyester, polyurethane, silicone coatings, vinyl ester, or the like may further cover the cured crosslinking polyvinyl acetate primer and then dried or cured.