There have been some recent project disasters and the root causes have been a lack of detail in the pre-engineering phases. Seasoned owners understand the benefit of spending a few dollars up front to avoid a huge mess later on. A further benefit of pre-engineering, is total project cost reduction because the design is purpose built not "previous +10%".
The building design is sorted out with known loads in the pre-engineering phase prior to the project being approved by the owner.
All of the major players in this industry allocate 6 months to a year for pre-engineering studies before ground is broken. I have only worked on one installation, 30 years ago, where there was no pre-engineering phase and that was a major challenge (Miramichi PM1). They broke ground before the machine was bought and startup was extensive. The whole project took 18 months start to finish (breaking ground to startup).
The critical difference between Euro/South American mills and a North American mill is the use of pre-cast concrete there versus structural steel here. Both have their advantages and disadvantages but pre-cast concrete is a lot heavier and typically the roof is also precast. A good example of this is comparing the Greenpac machine to the Mondi PM7 machine in Poland. Both are linerboard machines and are similar in trim width although PM7 is quite a bit faster. The footprint and height for Greenpac machine is a lot smaller than the Mondi machine and the Greenpac building is a hybrid using a pre-engineered structure (think tent) above the operating floor level. Having access to both sets of design data and drawings, I can state that the Greenpac machine room building is a lot lighter, per meter of length with the same cross section, than the Mondi machine room. Another example of light weight structures, like Greenpac, are the WestRock machines in Syracuse. I don't think we are behind the times when compared to other geo locations.
On to stacked dryers. It's a given that the foundation for a stacked dryer will be a lot heavier, possibly double the concrete mass of a similar high speed UniRun dryer section. However, all that concrete in front of and behind the dryers in the basement and operating floors is drastically reduced as is all of the mezzanine concrete and supports. Imagine reducing the length of a dryer section by 60%. That is one heck of a lot of space that disappears.
Maintenance would be no more difficult that removing rolls from a press section. Besides which, I haven't seen too many dryer cylinders pulled for any reason.