text: Most often it would say something to the effect of "If you approve my loan, I will start construction."\n\nSo using your words, "If you sanction my loan, I will start construction."  'Will' is not needed in the first half and 'the' is not needed, in fact should not be there.  "the construction" would be the noun version, where you are more than likely saying construction as a verb...If you act, I will act.  However, if it's a cause and effect sentence, you want it like this...\n\nAfter(or When) you sanction my loan, then I will start construction.