using FIDIC 99 yellow book, the Engineer has issued an addendum which is not clear but it could be explained and interpolated in different meaning. Is the contractor correct in refusing to execute the extra works included in the addendum based on ( why the engineer was not very clear on his requirement )
Thanks for your question.
The contractor has the right to refuse Engineer's instructions which the contractor feels are not adequately clear for execution purposes or it can not be implemented due to some local problem regarding supply etc. If the problem is regarding in non clarity in the specification or text of the issued written instructions, then i am of the view that contractor should have taken up the issue with the Engineer right at that time when he received the instructions from the Engineer(clause 1.9 relevant). If no such clarity was sought at right time, i feel the contractor should not refuse the Engineer's instruction and seek clarity now. This my response is as i understood your question. Please let me know if this is not the case.