Think of setting out as drawing the building's plan directly onto the site with pegs and string lines, a step that has to happen before any earth is dug.
- After the foundation excavation: if the trench is already dug, there is nothing left to mark for digging, so this order is backwards.
- After the foundation concreting: by this stage the footing is already cast in place, so setting out this late serves no purpose for the excavation.
- Before the foundation excavation: this is the natural order. Surveyors fix the centre lines and corner points of walls and columns and mark the trench width on the ground using lime or chalk lines and profile boards, and only then does the excavation crew start digging along those marks.
- Before the placing of plinth beam reinforcement: plinth beam reinforcement goes in long after the trench has been dug and the footing concreted, so this describes a much later stage of the same job, not when the first setting out happens.
Because setting out is the reference step that tells the excavation crew exactly where and how wide to dig, it has to be finished before excavation starts, which makes option (C) correct.
Let's summarize:
- Setting out means marking the building layout on the ground using pegs, lines, and profile boards.
- Its whole purpose is to guide the excavation, so it must come first, before digging.
So setting out of the foundation is done before the foundation excavation, option (C).