We have hired a contractor to do repairs and roofing on our home. He is using sub-contractors to do the work. We want to make sure that when we pay him, that if he does not pay his sub-contractors, or for materials received from suppliers, that they will not be able to place a lien on our house for their payment due. Does a lien waiver provided to us by our contractor insure that his sub-contractors cannot place a lien on our house?