When should I back off during construction salary negotiations?

You should never jeopardize your relationship with your boss over a negotiation. You don’t want to win the negotiation and lose the relationship.  If you feel you are pushing the limits of the relationship with your position, then back off. It is always best to let your employer know how much you appreciate the job opportunity, and do not want a money discussion to conflict with your good relationship. State your concerns and issues, and place your case in the hands of your employer to make a decision. If you don’t like the decision you should not fight it or push the relationship. You can respectfully disagree, but you should either accept it or move on to other job opportunities.  It is often best to get a third party involved to discuss money matters (such as the HR manager or recruiter to deal directly with your boss).