In a modular glazing system, a plurality of rafter units is affixed to stiffener arms of a plurality of node stiffeners so as to connect the node stiffeners and so that the rafter units define at least one polygonal shape. A frame unit is affixed to each rafter unit. An elongated spacer is placed on each frame unit. The elongate spacer has a glazing placement surface with a predetermined angular relationship to the frame unit. A glazing unit, having a shape corresponding to the polygonal shape defined by at least three rafter units, is placed on the glazing placement surface of the elongated spacer on each frame. Each glazing unit is sealed to the glazing placement surfaces and to the frame units.