In order to design a building, what component of the building should I design first?

There are multiple approaches to a design and no two architects may agree here. However, a pragmatic approach would be:

  1. First get the space program in place…ascertain the built up area required for each of the use.
  2. Get the site plan with the constraints marked…… constraints include site features, regulatory requirements like setbacks… Also ascertain the vertical stacking possibility. This would give you the foot print and the floors/stacking possibility to achieve the space program derived.