Abstract: A window frame includes a head, a one-piece stepped and sloped bottom sill and one-piece side jambs with integral sash and screen tracks. The side jambs, head and bottom sill are welded together at the corners, such that jamb walls attach to the appropriate walls of the head and sill to form a water-tight frame. The bottom sill is one-piece, with integral sloped steps that form the floors of the various sash and screen tracks. It includes an integral dam and integral internal strengthening walls that are strategically placed to support the otherwise hollow sill. The jamb, which is also one-piece, includes integral internal strengthening walls that correspond to the strengthening walls of the bottom sill, and integral track side and front walls that define the tracks for tie sashes and screen. These walls extend the length of the jamb and connect, when the frame is assembled, to appropriate walls of both the head and the bottom sill.