Why top down method of construction was chosen in a project?

Answer 1

Benefits of top down construction methods are
1. Suitable for 3-4 basement structure with high rise super structure.
2. cost & time saving for eg. Once 1st sty completed, basment and superstructure construction work can concurrently go. ie B4--B3-B2 -B1<<1st sty >>2nd sty - 3rd sty-4th sty.
3.Open cut method involve lots of temporay works and take time. ie superstructure could proceed only when all basement say B1-B4 completed.

Answer 2

Probably because it avoids hauling materials and equipment past finished parts of the project.