Window frame with jamb extender

A window assembly for installation in window openings having different thicknesses comprising:

• a) a window frame having parallel side jambs, a header and a sill, said jambs, header and sill having inner and outer faces and together forming a rectangular opening;
• b) a plurality of C-shaped clamps extending inwardly from the inner edges of said window frame jambs, header and sill, said C-shaped clamps having center sections attached against the inner faces of said jambs, header and sill, parallel inwardly extending inner and outer side arms spaced at a given width, and an inner side, the inner side having a rectangular space defined by the inner and outer side arms each forming a 90 degree angle with respect to the center section, said C-shaped clamps including inwardly extending gripping projections along its inner and outer side arms;
• c) a rectangular frame formed of four rectangular boards having lengths corresponding to the lengths of said frame jambs and widths corresponding to said given width, said rectangular boards having outer edges with a rectangular shape corresponding to the rectangular space of the inner side of the C-shaped clamps, said outer edges of rectangular boards being slidably adjustable in said clamps relative to said window frame;
• and
• d) a plurality of extender trim pieces forming an extender trim, said extender trim mounted on the inner edges of said jambs, header and sill and extending from the rear of said window frame along the inner sides of said clamps, said extender trim pieces flushly abutting the inner side of said clamps on one side and flushly abutting the inner edge of said jambs on another side of said extender trim pieces, said extender trim pieces having a width greater than the height of said clamps and including a flange over its outer edge extending over the inner sidewall of said clamps.