I live in Arizona and own a home where one of my exterior side-walls sits on the boundary of my property line and my neighbor's property line. My neighbor's home and my home are "attached" via a cement block wall between our two houses and this wall includes my neighbor's gate to his backyard and provides the only exterior access to that side of my house. My neighbor has a pool and his backyard (from what I can see since I can look out my window and straight down into his yard...yes it is weird and no we don't make a habit of invading their privacy) is completely covered in cool-decking and pavers. It looks nice, but as someone who lived in a house with same in Florida I know that water has to go somewhere when it rains. Unfortunately, from what we can see is it there is definite seepage from his backyard into ours under the block wall. This part would be no big deal as it seeps onto our concrete slab "'patio" and into our gravel pit of a backyard, but we have no visibility to where the rest of the water is going, presumably up against our house. We did have an issue where during a rainstorm a couple of years ago we noticed a small amount of water seeping up into our first floor bathroom which is along that same exterior wall, but the issue hasn't reoccurred since then so we're not sure what it was.

This is our first home and the more I think about this issue the more uncomfortable I'm getting. I don't know where the water is going. None of the houses here have rain gutters (ours included, so what do people in Arizona use for runoff? Water comes off our roof and hits about 2 feet from the side of the house), and even if rainwater were accounted for, any watering, pool overflow, etc could be draining right against our house and we wouldn't know it. It's his property so I really don't know what our rights are, if any, or if he has any obligation to mitigate damage/erosion/etc on his side. My husband did say something to him when that puddle showed up and he was like, sure you come dig a trench or something, but he has a giant shed right there so whatever we dug would be basically useless given the amount of space we'd have to work with.

I would like to have someone come out to inspect the wall, foundation, whatever on that side but obviously that requires my neighbor's cooperation for inspection, any repairs, any drainage mitigation, etc plus any improvements made on his property would seemingly be at my sole expense but would have to include his input etc (since again his property).

Am I in between a rock and a hard place? These houses were built this way in the mid-80s and people have coexisted just fine, though I can't fathom why someone would situate a house on a lot this way. My neighbor is generally pretty easy-going but it's been small things so far and I don't know what to expect if we told him his pavers would need to be torn into or something (I don't think I'd be happy, were the shoe on the other foot).

Any thoughts? Please & thank you.