This study aims to describe the effects of wood material (oriental beech) impregnated with ammonium sulfate, borax, boric acid, and zinc chloride by using two different methods (pressure and dipping) and finishes with the effects of different varnishes (polyurethane, cellulosic, synthetic) and paints (cellulosic, synthetic, industrial) on thermal conductivity. These materials were used as fire retardants. The lowest thermal conductivity of 0.143 kcal/m hA degrees C was obtained in oriental beech control samples. The highest thermal conductivity of 0.172 kcal/m hA degrees C was obtained in oriental beech impregnated with ammonium sulfate by using pressure and varnished with synthetic varnish. Consequently, wood impregnated with ammonium sulfate by using pressure and finished with synthetic varnish can be used as a construction material where thermal conductivity is required. Wood impregnated with borax by dipping and finished with cellulosic varnish can be used as a construction material where the insulation is required.