How was is to build a house in the middle age in europe? Where did people get the materials from? How long did it take? What were the differences between building outside the city and in the city? How many people did it take to build a house?
First of all, most people didn't really live in a house. Mud huts more like it. Cities were more likely to have wood houses. If you were powerful you lived in a stone house. There were no wood treatments back then and wood rotted if used in a structure. So although wood was used extensively in buildings, they didn't last as long as they do today. The exception is certain military and religious buildings made out of stone in basilica or roman styles. Construction took from a few months to years, involving a couple to hundreds of people, depending on the size.
As Christianity grew people moved away from Roman arch architecture to simple Gothic styles for churches. The main feature of Gothic architecture is the triangular shape of the structure rather than the arch shape used by Romans. This saved on materials and time. There was also Arab and Chinese architecture, which is a whole different story.
Fire was a major problem in cities and everything was crammed together and unsanitary. Cities like London held up to 300,000 people per square mile, and without modern skyscrapers and so forth to make the space problem easier. There was some limited urban planning, mostly by the people who had power in the city- guilds, monarchs, and merchants. However nobody ever solved the human waste problem.