Figure 5-2.—Foundation plan and detail.
Sources of Error
Omissions are usually the result of careless
Failure to read all the notes on a drawing or failure
to examine reference drawings results in many
omissions; for example, an estimator may overlook a
note that states “symmetrical about ~’ and thus
compute only half of the required quantity.
Errors in scaling obviously mean erroneous
quantities. Great care should be taken in scaling
drawings so that correct measurements are recorded
Some common scaling errors are using the wrong scale
and failing to note that a detail being scaled is drawn to
a scale different from that of the rest of the drawing.
Remember that some drawings are not drawn to scale.
These, of course, cannot be scaled for dimensions.
Sometimes a wrong interpretation of a section of the
specifications can cause errors in the estimate. If the
estimator has any doubt concerning the meaning of any
portion of the specification, he should request an
explanation of that portion.
examination of the drawings. Thoroughness in
examining drawings and specifications will usually
eliminate errors of omission. Checklists should be used
to assure that all activities or materials have been
included in the estimate. If drawings are revised after
takeoff, new issues must be compared with the copy
used for takeoff and appropriate revisions made in the
estimate.
Construction materials are subject to waste and loss
through handling, cutting to fit, theft, normal breakage,
and storage loss. Failure to make proper allowance for
waste and loss results in erroneous estimates.
Other sources of error are copying errors,
inadvertent figure transpositions, and computational
and arithmetic errors.
ESTIMATING BULK MATERIAL
REQUIREMENTS
All material estimates, including those for bulk
materials, are used as a basis for material procurement
5-6
