The origin of the author’s paper is a redesign of a Swedish pile-supported steel fiber concrete (SFC) slab for Friend’s Arena in Stockholm, Sweden, where the two different design methods summarized in the paper were compared. The design thickness of the slab was calculated to 350 mm (14 in.) and 450 mm (18 in.), respectively. This comparison was presented at the fib Symposium in 2012 in Stockholm in a paper coauthored by the author and one of the debaters.2 The real slab is 350 mm thick and as far as the author knows it works still perfectly well. On the other hand, the author has recently taken part as an invited expert in a couple of damage investigations where SFC floors have cracked severely due to insufficient thickness and/or too heavy loading. In Sweden, the two design methods still compete. According to the author’s opinion, contractors should compete by selecting and offering different technical solutions with connecting bids, but not by calculating in different ways. The attempt of the CI paper was to try to find probable explanations that the design method leading to smaller thicknesses often work well but not always. The author fully agrees with the debaters that we have to minimize the global waste of resources and not make the floors thicker and containing more fibers than necessary.