PURPOSE: To promote fire prevention and fire resistance by fitting wooden faces to both surfaces of the front and rear of a frame member formed in the shape of a face through reinforced members of wire gauze.
CONSTITUTION: Among the combination of a cation contained treatment liquid containing at least one kind selected among a group constituted of Mg, Ba, Ca. Al and Zn cation with an anion contained treatment liquid containing at least one kind selected among a group constituted of BO2, PO4, CO2, SO4 and OH anion after impregnating wood material with one of the treatment liquids the wood is impregnated with the other liquid to form flame retardant treated lumber. Then frame members 1 of the flame retarding lumber are assembled in the shape of a frame, and face plates 2 are fitted to the front and rear through reinforcing members of wire gauze. A space of the frame members 1 is filled with filler 4 to form a core. According to this constitution, fire resistance of a door can be promoted.
USUI HIROAKI
OTA YOSHIHIRO
YUSA YUKIHIKO
ISHIKAWA HIROYUKI
