Abstract: A modular building section defining the roof and opposing walls of a modular clearspan building. The building section includes a roof portion extending in a longitudinal direction between opposite first and second ends, and a pair of first and second legs, each leg pivotally attached about a pivot axis to the roof portion proximate a roof portion end. Each of the first and second legs has a stowed position in which the leg generally extends in the longitudinal direction and is in superposition with the roof portion, and an expanded position in which the leg depends from the roof portion and generally extends perpendicularly to the longitudinal direction. The legs are moveable independently of each other from their respective stowed positions to their respective expanded positions under the influence of gravity during lifting of the roof portion. Also disclosed are methods for constructing a modular clearspan building.