A system for mounting wall panels to an existing wall structure, includes wall panels, each having a main panel section and hook walls at edges thereof which define a U-shaped configuration therewith; fastening extrusions, each including a securing section for securing the fastening extrusion to the existing wall structure, and a female connecting section including a recess and connected with the securing section; a frame extrusion connected to each hook wall, each including a securing section connecting the frame extrusion to a hook wall, a male connecting wall engaging within a recess of one female connecting section, and a spacer wall connecting the male connecting wall to the securing section so as to define a gap between the female connecting section and the hook wall when the male connecting wall is engaged within the recess; and a cover panel inserted in the gap.