As far as JG King go, as mentioned in a previous post, it seems their steel framed houses have timber strut sub floors, so part of the problem with their own houses may be the relationship between the steel and the timber causing different rates of expansion/contraction which may result in more cracking and creaking. Caveat: This effect of the 2 different materials is my own personal theory and is not based on any evidence.
JB
Sorry if this is a stupid question, but what is a subfloor?