PWC recently polled wallcovering contractors and estimating experts to compile a list of the top 10 boners in estimating. There's no attempt here, however, to rank the mistakes in order of frequency or severity. First and foremost, computers ensure accurate arithmetic. Computers won't make little mistakes. The speed and ease with which computers add one and one or calculate the square footage of an eliptical ceiling take the pressure off harried contractors to use shortcuts associated with manual estimating.
Some software packages come with data bases on material costs and production rates.
There are, for example, object lines, hidden lines, center lines, dimension lines, extension lines, cutting-plane lines and break lines. If you mistake a center line for a hidden-object line, you might bid on more work than what's really there. Or, if you don't realize that break lines leave out redundant portions of a building, you might underestimate your work. They may discover, however, that their bid was too low because they failed to factor in environmental constraints. Rugged or muddy terrain may rule out the use of bucket lifts as the contractor had planned and force him to switch to swing stages, thus slowing down the project and dramatically increasing labor costs.