Building Design and Construction

Computer Estimating

There are essentially three types of commercial computer products useful in preparation of cost estimates:

Utilities. These are programs that arrange information or do arithmetic; for example, spreadsheets and report generators databases. Most estimating programs fall into the utilities category.
Databases. These contain raw information, for example, prices of plumbing fixtures, that the estimator must analyze and choose from.
Expert Systems. These are programs that question the estimator, then use the answers to produce an estimate. (Expert systems are sometimes referred to as artificial intelligence systems.)
Some commercial packages may contain two or more of these.
Computer aided estimating has now specialized with software blurring these distinctions. This goes across the construction industry where you see competitors using the same software with certain information customized. One sees a single brand of software in use by contractors and another by designers and yet another by home builders. Contractors tend to use utilities that talk to their expert system for material control and fabrication. Designers use specialized expert systems for the specific work they performed (i.e., environmental remediation), and the home builder may have sales people using an expert system that was created in a utility with pricing from window and door vendors.
19.7.1 Utilities
These enhance, but do not replace, the expertise and knowledge of estimators. They enable estimators to extract and summarize needed information rapidly and accurately.
Utilities are broad based; they can be applied to almost any estimating type, approach, and technique. Use of some programs is easy to learn; for example, spreadsheets. Others are difficult; for example database report generators. In general, the more powerful a utility is, the more difficult it is to learn to use it.
19.7.2 Databases
Generally, databases are designed to be used with one specific utility and one specific approach, such as industry or discipline (Art. 19.2). Some are limited to a particular type of estimate and technique (Art. 19.2.2).
The estimator should always be aware that a database responds only to specific queries asked in a specific way and cannot interpolate. For instance, if a database has the prices of 1⁄2-in and 1-in bolts and the estimator requests the price of a 3⁄4- in bolt, the computer will reply that the database contains no such price. At this stage, the estimator should devise the proper queries to solicit responses helpful in preparing the estimate.
19.7.3 Expert Systems
Generally, expert systems are even narrower in application than databases. Unlike databases, however, expert systems will respond to a query as long as the estimator operates within the limits of their area of expertise. They have several drawbacks:
They do not take into account creative solutions or project-specific problems. They do not change with changing technology. And they tend to be very expensive. As a result, they are not widely used.


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