Building regulations

[SuzieQ]

I have seen this question from a few months before, but still wonder what I could do.

When we bought our property, and built our house, we got written consent from the neighbors to build up to 30 cm of the boundary. That was very nice of them. And I know that they didn't have to sign that.

But now, they are building a construction right on the other side of the boundary. With a wall just as close to the boundary and a roof right until the boundary. I guess it is going to be a water tower. And I'm afraid the walls are there just to obstruct our view.

I wondered if they didn't need our permission for that.( My husband says that he would have given it anyway, since they gave us the permission as well.) I'm not that sure yet. At least, I would have liked to have know about their plans. Besides, I worry about the roof and rainwater running on our walls.

So far, the construction is about 5 meters wide and two floors high. And connected to the construction is a wall of the same height (with no building behind it), running along our entire property.

Can they build a wall of 6 meters high? Why didn't they needed consent from us? Because it is a water tower?

I am really annoyed. They have 4 rai of empty land and build the thing within a meter of our house.