Why do my neighbors dare think they can build decks overlooking my house?

To clarify, It s not my house but my dads house but he feels the same way. My neighbors built obnoxiously placed, large decks that obscure my view of the backyard and worst of all, allow them full view of my room, my parents bedroom, the kitchen and the basement. So my neighbors now know what our house looks like at all times.

How is this legal? The houses didn t come with decks, they bought some cheap wood and hired people to build it who I saw with a ladder on my house - I saw the guy climb up over my window. And in just 3 days of labor, the view of the sky, the trees, and our privacy was destroyed… Oh, and they're all smokers so now we have to close the windows to preserve clean oxygen.

I can no longer walk around my house without clothes. I can no longer leave the blinds open to see the sky my parents payed $2-300,000 to have. I can no longer enjoy the pure air only the backyard had, or the landscape that was once just trees, grass and sky.

Now I feel like I have to wave hello to the neighbors in my own house, I'm like a zoo exhibit. And they do look in here, they watch carefully and I can tell because It's awkward seeing them now. I feel anxious looking out the window because my neighbors head will pop up in front of it, he'll turn around and look at me like I'm crazy.
Added (1). We had a big glass window in the kitchen that we enjoyed, now my parents covered it with a big drape because of the decks.
Added (2). They know perfectly well they're violating my privacy but they won't mention it or tear down their cheap splintery eyesores. They know "Wow, I'd hate to be violated like I'm doing to my neighbor" but they choose to stay silent knowing I can't fight.

All my life my father has worked to afford this house, pay the mortgage and now these people take away the peace he worked hard to achieve. All that research, moving here and finding this place, all ruined.

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