The cities are looking great so far but I do have one question. Are there any plans for, humans at least, to avoid building into the sides of hills? Right now some of the shots remind me of the Shire. In my family's first home there were huge steps cut into the hillside on which homes were built and walls to hold the dirt back but never have I seen a house surrounded on most sides by dirt like in the shots you posted. Perhaps some landscaping would solve the roof walking problem?
I have spent most of my childhood in a 400 years-old house with the ground at roof level on the rear and left side, and a slope on the right. The walls were mostly made of stones approximately 60cm, 20 cm and 30cm of length, width and depth respectively. This house used to be the servants' quarters back then, and a few centuries before, the building it was built onto was a stable.
So nope, it was done at that time. It's not the most likely to be found, but it was lovely. Only bad sides were that it was litterally freezing inside in winter (it turns out having a few tons of wet soil behind a stone wall does not help with humidity either). Oh, and the walls slowly curved and will probably keep on for only a few decades now.
Good sides : temperature was perfect in summer.