Z clauses (in my experience) are the still the biggest cause of argument and dispute on projects – not the original unamended NEC3 clauses. I have compiled a list of the common ones to look out for that (in my opinion) are not generally well thought out by Employers who are advised to include them. This should form a starting point check list to which Contractors should look our for and consider the implications that they would bring. Contractors can then either try to get them written out of the contract or at least be able to price the risk that they bring (or do what I have done on at least one occasion and walk away from a tender that was so heavily amended and almost impossible to price)
I hasten to add that this is NOT a list for Employers of new clauses that they should include!