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The Danger of Making Assumptions When Estimating

April 14, 2023
Understand these 10 elements of estimating.

The word “assume” means “to take for granted; suppose.” Most estimating departments are fast-paced environments, which requires the estimator to read many specifications in a short period of time. You may be tempted to review the project documents too casually, causing you to take some things for granted or make assumptions. However, you can minimize or eliminate assumptions if you have a good understanding of the following 10 items:

  1. Scope of work — When bidding on a plan and spec project, typically the scope of work is provided in the specification. This specification section will provide the estimator with work to be performed by the contractor. Sometimes, a scope of work will be provided in Division 26 of the specification. This summary of the work can (and may) list work items that the contractor is responsible for. If there is no scope of work listed in the bidding documents, the wise contractor will write one that details the components included in his or her bid price.
  2. Division 1 of the specifications — Some refer to this section as the “front end” of the specification. The bidding documents are found in this section and typically include the following: advertisement for bids, instructions to bidders, bid forms, and the agreement form or contract. Also in this section are the general conditions and supplemental conditions of the project. The general conditions set forth the rules by which the project is constructed and administrated. The supplemental conditions deal with the project’s specific matters related to the contract. Supplemental conditions may also modify items in the general conditions section.
  3. Schedule — The project schedule may be indicated by one of two means. It may give the contractor a number of calendar days, such as 150 days or a fixed calendar date. Regardless of the means, the estimator must understand the schedule. This is vital in determining supervision, equipment rental costs, labor rates, and, most importantly, crew size.
  4. Phasing — Some projects require portions to be completed in succession. The phasing drawings will usually indicate specific areas and the completion dates these areas must be completed. Depending on the phasing requirements, the contractor may have to mobilize and demobilize several times over the course of the project.
  5. Shutdowns — Renovation projects are known for having shutdowns. When the project requires an upgrade to the electrical service, this is typically done on the weekend and will require overtime. In an occupied facility, the circuitry may need to be fed from a new panel — this work typically will need to be done on off-hours to avoid interruptions to the owner.
  6. Building construction — Not all buildings use the same wiring methods. For example, a high-rise condo structure with poured concrete walls is not estimated the same as a multi-residential housing project. In an industrial environment, areas with corrosive materials are estimated differently than areas that require explosion-proof equipment. Both material and labor costs are affected in these different areas. Understanding the building’s construction is vital.
  7. Technical specifications: Divisions 26, 27, and 28 — Technical spec sections have three headings: 1) General; 2) Products; and 3) Execution. The product heading will typically list each product specified with acceptable manufacturers and catalog numbers. The execution heading will detail how the material is to be installed. One example would be conduit installation. For example, PVC conduit may not be permitted to be installed in the slab or underground, where on a previous project this means of installation was permissible. The estimator must completely understand these sections of the specification, paying careful attention to the execution heading.
  8. Check scales on all drawings — It is not uncommon for drawings to have different scales. In rare cases, a drawing may have two areas shown, each with a different scale. Quantifying materials on the wrong scale can be detrimental to the estimate’s accuracy.
  9. Check match lines for overlapping items — Some projects require more than one drawing per floor. When this happens, the architect provides match lines. Sometimes, items are duplicated on two drawings.
  10. Check column lines — This is very important in multilevel buildings. For example, the main electrical room may be in the basement, and a new panel is being installed on the 4th floor. The vertical length is typically easy to determine. But the horizontal length can be a challenge. This is easily accomplished by identifying column lines of the project. Assuming that the electrical room is directly below is risky, especially when estimating a large feeder.

Making too many assumptions is unwise. The fewer you make, the better. Just remember that estimating is more of a science and less of an art — so treat it as such.

Don Kiper is an independent electrical estimating trainer and consultant based in Niagara Falls, N.Y. He can be reached at [email protected].

SIDEBAR: Check Your Symbols!

Here is one example of how not every engineer uses the same symbols for devices on the drawings. Below are four different symbols for a fire alarm smoke detector used by various engineers.

Review the symbol legend carefully for each project you estimate. Having to recount devices for various systems because “assumptions” were made will waste valuable estimating time. You can make another dollar, but you can never make another minute. So place a high value on your time!

About the Author

Don Kiper | Independent Electrical Estimating Consultant

With more than 35 years of experience as a construction electrician, industrial maintenance electrician, foreman, estimator, estimating manager, and project manager, Don has used what he learned to lead in the implementation of estimating software with three electrical contractors where he has worked. Don has 17 years of experience in the construction field and 18 years of office experience and he has personally estimated over $700 million dollars in electrical projects. 

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