High quality budget of a building can save much more money than the cost of the budget itself. Many investors have convinced themselves about the truth of the above mentioned statement when in an effort to save money during the building preparation process they did not have the budget, eventually some had the budget processed according to the project for building permit that unfornately does not include all specifications.
Since the price bids are assessed by the contractors according to the documents sent by you - items that are not included in the budget are not assessed and the contractor will ask for additional funds which were not included in the budget.
The fact is, that it is not possible to create a perfect budget for large scale projects, additionally these projects are usually modified during the building process according to actual conditions on the market. This is not to lower the significance of the detailed itemized budget, it only means that some items are replaced by others, some of them are lowered or increased in quantity, but essential is that the investor has the control of the funds for the project and in every particular moment knows the price of each item and its quantity.