The popularity of lump sum bidding provides cost assurance for the developer but puts the financial risk on the general and grading contractor. To ensure profitability on earthwork jobs, these contractors rely on their estimators to accurately calculate quantities and provide validation to prove their numbers and get paid.
Accuracy Reduces Risk
Successful estimators must understand how to read data from the plans and how demolition, stripping of topsoil, or removing contaminated material affects site quantities. They also need to adjust the proposed grades to subgrade and quantify the cuts. The fills need to be itemized by structural and non-structural regions to determine if any or all the cuts can be reused. This will determine if the design is balanced or requires expensive import or export of material. In some projects, foundation over digs and phased construction complicates the takeoff even further.
The difference between an estimate with accurate quantities or miscalculations directly impacts both winning bids and how much profit is made on the job.