Estimating with Prefab

By Stan Shook | Jul 15, 2008




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I don't mean to be a fearmonger, but there’s a lot of talk about a manpower shortage in our industry. This is a big problem. Let’s be optimistic: From big problems come big solutions.

One big solution, which I believe will soon become the standard, is prefabricated (prefab) and modular wiring systems (MWS). The concept is not necessarily new. Contractors have been prefabricating electrical components in their shops for many years. MWS also has been around awhile, mostly with lighting circuitry installations. But it faded a bit into the background because there were material cost issues, and the industry-wide use of MC cable pretty much beat it into submission.

As to this use gaining strength in our industry, Cablofil/Legrand recently purchased PW Industries, a leading innovator of prefab products. If these guys are involved, you know it’s a big thing.

The company’s new product line is called FAS Power. This is a major component addition to Cablofil/Legrand’s already successful VE Plus system of productivity-enhancing installations, which integrates the use of welded wire cable tray as a pathway for carrying MC cable branch circuitry and power distribution feeders (yes, I wrote “feeders”).

The VE Plus method and systems already have proven increased labor productivity well over 35 percent on hundreds of commercial projects nationwide. With the addition of FAS Power, the system now is capable of accommodating well over 75 percent of a project’s power system installations. It is safe to say this will result in more than 50 percent increased labor productivity. Fifty percent!

How do we estimate prefab?

Estimating prefab and MWS projects is not that complicated. It simply requires a different mindset. There are two basic scenarios: re-engineering an already designed project or design/build engineering a project from scratch. The latter will certainly be easier, as you will have more control of what you can use and where. Also, you won’t have to worry about making changes to someone else’s design.

The predesigned project becomes a challenge in that you must convert all the device-to-device circuitry that runs into modular connection items. So, instead of rolling off and marking up 300 feet of 1-ckt runs, you now will have to measure out each run between two devices and enter them in as a count. Homeruns are not that different. Basically, you will have a modular whip connecting the last device to a homerun J-box.

In my recent experiments with estimating prefab, the device counts take about the same time as nonprefab, though I have found the roll-off phase took a bit longer. However, I am always finding more creative ways to do this, and it should eventually become a faster takeoff.

You can’t forget or leave out the old ways of pipe and wire. You still will need to use those methods in tandem with the new modular installations. For example, your homeruns may be 50 feet or longer, and it may not make much sense to order (if they are even available) modular homerun cables. Plus, homeruns often are combined into larger conduits. This already saves materials and labor costs, and I doubt you could do better with prefab.

CAD estimating just got easier

I believe estimating prefab and MWS components will be easier and is a perfect match for symbol recognition and CAD takeoff software, especially if you have control of the design. By assigning database items to every symbol, your prefab design can be counted very quickly and more accurately than if you had to count the ups and downs of standard MC or pipe branch circuitry.

Also, using a CAD estimating program allows you to create detailed drawings for the field while you estimate. These drawings would identify each modular device and circuit run by part number and length. This is really important because you must make sure your electricians know exactly how you estimated the project, which products you used, and exactly where and how you used them. This is always critical to any job’s success.

Know your components

Nothing comes without its required learning. Prefab systems have many components and even more combinations of them. You should take the time to learn which system is best for your company and learn the catalog well.

For basic estimating purposes, you may simply want to create a database of items using generic names and descriptions. Using generic items allows you to submit your bill of materials to multiple vendors and obtain multiple pricing quotes. As for the modular MC cable circuit whips, well, you can simply name them something like 10-foot, 1-ckt, No. 12, dual-end terms or 20-foot, 3-ckt, single-end term.

The world has become a modular, prepackaged place. I believe we are seeing a paradigm shift in how electrical systems are going to be installed and which materials will be used. Prefabricated systems will soon become the norm. Estimators will need to reprogram their minds and retool their databases for estimating with prefab and MWS. They need to begin thinking about the new ways and leave the old ways behind.

SHOOK is the president and chief estimator for his estimating company, TakeOff 16 Inc. He has worked in the electrical construction industry for more than 18 years. Reach him at 707.776.0800 or [email protected].

About The Author

Stan Shook was ELECTRICAL CONTRACTOR's estimating columnist from 2005 to 2012. He works as an electrical estimator in California. Read his blog at or contact him directly [email protected]





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