Question about unresponsive neighbor landlord

[Casey Crowe]

Hey guys, 

I'm currently renovating a condo, and it shares a single wood framed wall with another unit next door. (The other side has a cinder block wall). Essentially, the neighboring unit was recently renovated and rented, and there's now (and has been) water leaking onto the concrete slab, and through the bottom plate of the wall, and into our unit a little bit. 

The bit coming into our unit seems to have stopped but the wall is still moist and harboring mold. What kind I'm not sure. 

I've contacted the other landlord *numerous times* to fix the leak and abate the issue on his side, as cleaning it up on my side is pointless until the water stops. I've sprayed it multiple times with heavy duty vinegar to help cut it down, but of course it's continually being fed water. 

I have a long chain of text messages between myself and this landlord, including pics of the issue and he refuses to address it. At first he seemed to be skeptical it was his unit, until he came over and I showed him how my water pipes were cut open and dry. (Water had been off to my unit for months). He promised to get someone out, and keeps slow rolling and delaying the situation. 

What's my best steps to get him to do his job? I don't want to make an enemy of him, and I've been extremely patient, but I'm about to get this thing finished and I can't have this going on much longer. 

Any suggestions? Do I need to report him to a housing authority, or send a letter from my lawyer? What say you?

Picture below to see what I'm talking about.