19 plastic building materials, namely, plastic stair treads, plastic wall linings, plastic shelf boards, plastic wainscottings, plastic floor boards, plastic boundary marking posts, plastic ceiling members, plastic building panels, plastic building panels for luminaires and plastic building panels for illuminated signboards, having an excellent light diffuse reflection, attached to a metal plate; plastic stair treads, plastic wall linings, plastic shelf boards, plastic wainscottings, plastic floor boards and plastic boundary marking posts for building, attached to a metal plate; plastic building materials, namely, plastic stair treads, plastic wall linings, plastic shelf boards, plastic wainscottings, plastic floor boards, plastic boundary marking posts, plastic ceiling members, plastic building panels, plastic building panels for luminaires and plastic building panels for illuminated signboards; synthetic non-metal building materials, namely, stair treads, wall linings, shelf boards, wainscottings, floor boards, plastic boundary marking posts, ceiling members, building panels, building panels for luminaires and building panels for illuminated signboards; prefabricated building assembly kits for making non-metal prefabricated buildings