Do you prefer detailed BoQs or high-level estimating early on?

A question that often comes up on projects:

In early project stages, do you prefer:

  • A detailed Bill of Quantities, or

  • A high-level estimate with allowances?

In reality, we often don’t have enough information early on, but clients still want reliable numbers.

Some approaches I’ve seen:

  • Start high-level, then refine as design develops

  • Build early BoQs with assumptions

  • Use historical project data

  • Apply cost/m² benchmarking

My personal view is that it depends heavily on:

  • The stage of design

  • The client’s expectations

  • The risk you are willing to carry

Would be great to hear how others handle this in practice.