Damp house! How do I rectify?

[JohnD]

Stepped foundations.

Each house should be horizontal

There were lots of badly built old houses

But most of them have fallen down so you mostly see the good ones.

 

[GillObrien]

This is what I was trying to explain about all the houses on my street being on a slope but they're all aligned. Mine is like the first picture so how could they've been built with level foundations?

There are thousands of houses where I grew up that are like this - the roofs slope parallel to the road, and aren't stepped horizontal. Which I assume is why the back looks wonky because the extension roof is horizontal . Not that it helps with the damp.