We had a similar experience to another person on this site. We too had an entire house install of tile in 2011 and their story is almost carbon copy to our experience with Niemann. We were adamant on materials and time frame for install and although this is one of the most expensive installers in the area, they assured us repeatedly the materials we wanted and the time frame for install were "easily doable" as they had a full "staff" of highly screened installers and they guaranteed their work.
After paying a sizable deposit on the project, we were told the materials were not available and we had to choose a substitute from whatever they had left in the warehouse. When we threatened to pull the project completely the materials magically became available. Then after materials were delivered and start date was set, we get a call that there are no installers available for three additional weeks. When we demanded another installer, they confessed that these people are freelance contractors, not staff at all and they had no control over their schedules or availability.
This should have been our clue to pull the plug but we persisted. In the middle of the job, contractor decides to go on vacation and will need another two weeks to complete an install that we were promised would happen in five days. Then near the end of the job, Niemann attempted to tack on additional costs for work that was supposed to be included in original price. We were also over-billed for prep work that was never performed (turns out it wasn't needed) but because we agreed to the work in the estimate they gave us were expected to pay. That's like a mechanic giving you an estimate for an engine overhaul they tell you you desperately need, only to find out all you needed was an oil change, but since you were willing to pay for an overhaul, they're gonna charge you for one anyway.
Numerous calls to owner, Zack Niemann were ignored because he is, in my opinion, too cowardly to defend his unethical business practice.
This place is classic "bait and switch" from start to finish. Spare yourself the grief and expense, take your project elsewhere.