Modular staircase and method of constructing same

A modular staircase frame for supporting removable treads in the construction of a staircase, the modular staircase frame comprising:

• two opposing sets of laterally spaced blades, each of the two opposing sets of laterally spaced blades comprising a plurality of adjacent blades, each of the plurality of adjacent blades defining a plurality of spaced apart openings, each of the plurality of adjacent blades being adjustably connected to a connecting blade for connecting two of said plurality of adjacent blades, each of the connecting blades defining plurality of spaced apart openings for overlapping the plurality of spaced apart openings defined by the plurality of adjacent blades, the connecting blades being adjustably connected to the plurality of adjacent blades by a fastener received through the spaced apart openings of the plurality of adjacent blades and the connecting blades, the plurality of adjacent blades being connected by the connecting blades to define an adjustably spaced ascending formation relative to a proximate adjacent blade, said two opposing sets of laterally spaced blades defining two laterally spaced ascending frame members, said two opposing sets of laterally spaced blades including
• a first pair of opposing laterally spaced blades each defining a flange extending laterally therefrom for anchoring said first pair of opposing laterally spaced blades to a first surface, and
• a final pair of opposing laterally spaced blades remote from the first pair of opposing laterally spaced blades, each of said final pair of opposing laterally spaced blades defining a flange extending laterally therefrom for anchoring said final pair of opposing laterally spaced blades to a second surface,
• the modular staircase frame further comprising at least one stiffener extending between the two opposing sets of laterally spaced blades, said at least one stiffener comprising two slidably connected overlapping panel members, each of said overlapping panel members defining a longitudinal groove, the longitudinal grooves of the overlapping panel members overlapping for receiving a fastener through said overlapping groove, whereby the overlapping panel members are movable between a plurality of intermediate positions for adjusting the length of the at least one stiffener, the at least one stiffener including a fastener for fastening the two overlapping panel members at a selected one of said plurality of intermediate positions.