Monthly Archives: August 2009

Update #1 to BIM and Electrical Estimating

I just finished reading a great article about estimating with BIM (Building Information Modeling). The link to the article is below.

http://www.aecbytes.com/buildingthefuture/2009/ModelBasedEstimating.html

I did however, have a problem with one of the statements made in the article. Consider the following:

“In addition to the cultural shift and “buy-in” challenge, there is also the question of who will pay for the transition from one software to another. Should it be the owner of the project interested in adopting model-based estimating or should it be the design-assist subcontractor, who will benefit from the set up repeatedly on other projects?”

Did you notice that the question did not include architects and engineers as possibilities to pay these costs? It struck a sour note with me, as designers are pushing more and more costs down to the subcontractor, mostly in the form of incomplete and poor quality documents.

This may be a moot point, since I do not believe that hard bid electrical contracts will ever see a BIM model in my lifetime. The question was accurately stated when it referred to “design-assist” subcontractors. Design-assist is the only area that I am aware of using BIM modeling at all, and then, only on the largest of projects.

If you are using BIM for anything, please make a comment. I would like to know if it is a benefit to your operation.

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The Electrical Estimate From Hell

I actually started to write this earlier, and it turned into an angry rant. So I erased it and started over. Here you go.

We just finished the electrical estimate from hell. Even though I brought document quality issues up a few posts ago, I feel I need to revisit the issue. This project now tops my list of the worst set of drawings ever. There were 170 electrical sheets. They replaced 160 of the plan sheets to fix the holes and mistakes. They also issued over 100 answers to electrical question on 8-1/2″ x 11″ sheets.

The types of problems covered the entire spectrum possible errors. Here are just a few. 

  • Detail symbols were missing in many places.
  • The actual details referred to by the symbols were missing or wrong, such as a reference to a pole base that showed a manhole instead.
  • Duct banks ended up with no connection to the destination.
  • The duct bank details were missing many required conduits, but included conduits that needed to go in the opposite direction.
  • The feeder schedules were missing many conduits called out in details or on floor plans.
  • Conduits schedules specified feeders in the wrong building.
  • The time allowed by the specifications for shutdowns were less than half of what was required.
  • The specifications called for 24” of cover over duct banks. The detail called for 30”
  • The drawings were not specific regarding encasement. This simple question was not answered till addendum 5, and the answer was to encase everything, including underslab and site lighting. This addendum was issued one week before the bid, and required changing over 1,000 lines of takeoff.
  • Someone gave two different sets of switchgear the exact same name. They even confused themselves with this one, sending many feeders to the wrong building.
  • Feeders were routed through completely blocked areas. The answer was figure it out yourself.

As an estimator, this kind of engineering and drafting raises a major concern for me. That is the cost of estimating. The document quality on the project near doubled the cost of this estimate. It went from about two hundred hours to three hundred and twenty five.

Does anybody have any insight about this trend towards poor engineering? It is showing up on all types of projects, large and small. I am starting my own research into what has changed in the design process. I will post new information as I get it. Please let me know what you find out.