Back in the mid-1980s I gave one of our main clients (a water district) fee proposals to design a 2-million gallon AWWA D-100 water tank and a booster pumping station in a building. I had two fee proposals because the water district and a land developer were going to share different percentages for the design and construction of the two facilities.
The tank design fee (no bidding or construction services included at this point) worked out to about 3.5% of construction, while the pumping station fee worked out to about 11% of construction. The water district's chief engineer gave me a really hard time over this because he thought both fees should be right at the "magic 6%" that everyone touted back then. This was the first and only time he did this to me. All the other times, he was pretty easy to work with.
I first explained that I can design a water tank pretty cheaply because tanks are simple (thus easy to design from a civil perspective), contain lots of steel (thus relatively expensive to construct), and the structural design is delegated to the tank fabricator's engineer. I also mentioned that the fees for the previous half-dozen tanks I had designed for him were all in the ballpark of 3%-4% of construction. I further explained that pumping station design is expensive because it's far more complicated: the pumps are relatively cheap compared to engineering required to select the correct pumps (i.e. water modeling and browsing paper catalogs) and multiple disciplines were involved, including architectural, electrical, and structural. He still didn't buy it.
Then, I explained that with the 3.5%/11% fees I had come up with, the total cost to the water district would be less than if both fees were 6%. This he bought.
Fortunately, I had prepared both explanations before meeting with him.
I have run across a few other people in government who only remember the "magic 6%" and forget that the curves are actually curves and that the 6% is for a limited scope of work (i.e. design) for a relatively simple project of a specific size and that it doesn't include things like preliminary studies, surveying, geotech, etc. In today's world, we now have storm water plans to prepare, more extensive environmental documentation, and bunch of other stuff that the curves did not address. Even simple projects are complicated now, which means that any type of published fee curve would hurt us more than help us.
I have worked mostly on the public works and industrial sides of civil engineering, so I have generally been able to get the fees I need to do the work right. With good documentation, such as a detailed work breakdown structure with hours assigned to each task, I rarely get signification push back on fees. I often have to trim a little, but I have never had to trim a lot. I do understand the difficulties in the development market, even though I have done very little there. However, at my last firm we had a group that did only subdivisions. The top couple engineers in this group were almost always able to get reasonable fees from developers. The secret was working mostly for medium to large and well-funded developers that they had "trained".
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"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill