“Suppose one of you wants to build a tower. Won’t you first sit down and estimate the cost to see if you have enough money to complete it?” – Luke 14:28
Typically, the first question Quantity Surveyor's are asked is “How much will it cost me to build a...?”
Cost certainty evolves, just as design evolves; at the concept stage of a project.
It is difficult to derive an accurate forecast of construction cost, as many variables in design have not been resolved at that stage. The Client might be enquiring about a house – but there are many types of house, and even if two houses are identical, their construction cost will differ if one is on stable, accessible land and the other is in a remote area with poor ground conditions.
In fact, for most projects the final cost is not known until the final account is settled.
Cost planning is about gathering as much information as is available at any stage and incorporating it into iterative estimates, monitoring changes in design and consequential influences on cost.