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Estimating Detail |
Estimating Detail
The acceptable level of detail of an construction-estimating is a contentious subject. What's worse, estimators often disagree on what makes an estimate more detailed than another.
The commonly repeated answer is this:
As detailed as possible, given required turnaround and available estimating resources.
This analysis is flawed because it implies more time ought to be preferred, when the reality is that when considering larger organizational factors (strategy), ideal estimate certainty is likely far lower than most expect.
The correct correct answer involves optimizing for these factors:
- value of increased bid certainty
- value of increased estimate volume
An estimate's detail is irrelevant to its quality. A less detailed estimate is a more risk bid, but it is not the role of the estimator to determine acceptable risk.
Experiment
Perform a system takeoff (lighting for example) in exacting detail, the maximum amount you would ever consider using, and measure the time required to do so, as well as the cost of the scope.
Have another estimator takeoff the same scope using the proposed time saving strategy.
Repeat the test on additional projects.
Treat the detailed takeoff as the true value and find the error of the time saving strategy.
\frac{d\sigma}{dt}
Expectation
Time-saving strategies will overestimate or underestimate detailed takeoff depending on the assumptions used in their creation.
Human Error
It is commonly understood that a "detailed takeoff" is more "accurate" than a square foot estimate.