design for cost estimationbidding

huangyhg

design for cost estimation/bidding
when trying to obtain material quantity of say a 5-10 storey reinforced concrete building, how thorough would your design be? how long do you spend? how close would your rebar and concrete quantity be to that of the final design? again, this is for cost estimation/bidding purposes only.
clansman
if a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." code of hammurabi, c.2040 b.c.fff">
use price per square foot for buildings built recently and similar in scope.
there is a big difference between cost estimating and bidding.
cost estimating may be used for different things:
1) to justify a project
2) to select a type of system
3) to select a contractor to work with
hard bidding is normally used to select a contractor out of several based upon complete contract documents.
what is the purpose of your documents? will there be time given to refine the design? is the bid just an estimate or a firm price?
preliminary drawings for cost estimating and bidding can become a huge problem. a contractor can not bid that which he can not see. i have had situations where the preliminaries were used for budgets by a cm and we (the ae) were blamed for the costs increases for items on the final drawings. on another occasion the added items or refined details of the finals became extra costs over the gmp.
i have had cm's state they can gmp a project based on 35% drawings. but in reality they budgeted, guessed and delayed until they had 100% drawings.
the best course of action is to make sure all parties are aware and have the same expectations. the designer is always, always the fall guy when it comes to contractors and costs. cya