1-The Size of expansion joints in a building are usually determined by the engineer. Historically joints above 4" were used in seismic areas.

Buildings in non-seismic areas required 1" to 4" joints. But today many buildings in  non-seismic areas  are using larger joints.

2-What are the required minimum and maximum joint openings? What size is the engineer calling for? Is he expecting 4" wide joint or 4" of movement? A 2" wide joint with +-50% movement provides 2" of movement. A 2" cover with +-100% movement offers 4" of movement.