Damage to property by neighbour

First get a legal notice issued to him, warning him that if needed repairs are not done within a month, you will be forced to proceed further legally and also get the repairs done immediately with your costs which has to be reimbursed by him with interest and compensation for harassment.   It is your property that is being damaged and exposing you to hazards and you have to take adequate care first and your efforts in the past reflect in your notice with such photographs enclosed to the notice.

Contact your local advocate on jurisdiction and future course of action legally and to bring such orders restraining him the use of that particular toilet.  This is the reason why you have been advised to have photographs and issue legal notice to bring on record the violations.   This is applicable in all cases.  The workers that attended the work or any Engineer's certified report on earlier damages and cost of works is sufficient if your neighbour refbuts your claims for past repairs.