It is agreed and understood the otherwise subject to the terms exclusions provisions and conditions contained in the policy or endorsed-thereon and subject to the Insured having paid the agreed extra premium section III of this insurance shall be extended to indemnify the Insured for liability in respect of total or partial collapse of any building or structure caused by or resulting from vibration or removal or weakening of support. Cracks of all kinds including subsiding, settling, tilting or sinking of the surrounding building or structures are not covered.