Which measurement to enter
Use the stated base or floor footprint from the exact model's installation drawing. A nominal model size or maximum roof dimension can produce the wrong base.
A base is more than its area
The finished support must also be level, square and suitable for the building's bearer layout. Ground conditions, drainage and base construction are site-specific. Follow the building and base-system instructions rather than treating this area result as a materials schedule.
Check before work begins
Confirm who is responsible for the final dimensions, tolerances and levels. Record the drawing revision beside the result so a later product change does not go unnoticed.