I'm lost on how to handle an issue we are experiencing.  I live in Baltimore, Maryland.

I'm a private landlord in Baltimore City.  My neighbor is a non-profit organization that provides apartments and shelter to disadvantaged citizens looking to rent.  He is not the best landlord and has legal issues with his tenants at the moment.

THE SITUATION:  We had been having a leak in our 2nd story unit of a 3 level townhouse.  The leak occurred during excessive rains.  We had done everything we could on our side thinking that the water was entering our home.  We repaired the mortar on our walls facing the outside.  We  had a new roof put on and had it inspected with no issues.  We made sure our gutters were always cleared and have leaf blocks over them.

When it still continued, my contractors noticed that my neighbors gutters were blocked and that there was a 4" by 2" by 2"  hole behind the gutter where the wood or brick had disintegrated.  I took photos and shared them with the neighbor.  I did this a year ago (Oct 2020) and received assurances from the neighbor that the issue would be taken care of.

In the most recent rainstorm, the leaks occurred again.  My tenant just informed me that it continues to happen, but not as frequently.  We hadn't had excessive rain for quite some time, and the tenant isn't home all the time so he had not seen the problem.  

I sent roofers up again to see what had happened.  My roof again was in good condition with no issues or need for repairs.  Contractors assessed our bricks and mortar, which had not issues.  My neighbors gutters were clogged and the hole is still there.

I am now convinced that the neighbors neglect of fixing the hole is the cause of the leak.    I'm not sure what to do at this point.  He is not responding to my calls or emails.  I've sent him the new photos showing the same hole.  I did unclog the top part of the gutter, but the downspout is also clogged.

I'm going to have to rip out the areas that are damaged by the leak.  Do I need to go to my insurance?  Do I need to sue him for his carelessness?  I don't know if I can even prove the issue is due to the hole, but that is the only logical place the water can enter at this point.

Has anyone encountered this type of issue?  I'm not sure where to start.

Thanks.