Hi sir, first of all please check the contract agreement, there should be definitely a clause providing for such damages, just in case where the said clause is not available in the agreement, you need to do the following:
step1: assess the extant of damage in terms of money and in terms of time hours lost.
step2: get this statement cross verified by the external auditor, under a certification of the total amount.
step3: issue a letter (under registered post acknowledgement due RPAD)intimating the nature and extant of damage to the contractor
step4: if the value is high start deducting in installments, else recover the entire amount in the immediate next bill.
step5: issue a letter to the contractor enlisting the future course of action at such incidents.
setp6: you can also proceed against the said contractor and file a police complaint under the provisions of IPC \"willful negligence act such as to damage or destruction of the property and endangering the co employees peaceful w