I am listening to Ken Follett's newest historical fiction about this time period. I cannot get over their living arrangements. Listening to other books about medieval Europe, I just don't grasp why a peasant would want to share a room with their who family without privacy. So maybe they don't want to share a room, why would you not just build a few more rooms for privacy?
Thank you for your time!
Short answer: money.
Long answer: still money.
To start with, medieval peasants did not live in shacks. A shack is a dwelling made of salvaged material. What medieval English peasants mostly lived in was a cottage. Different materials were used in different areas but mostly they would be made with a wooden frame with walls made of wattle and daub. For those areas that were highly forested, such as parts of Central Europe, the Nordic Countries, parts of Eastern Europe, you would have houses made of wood logs or even hewn boards. The Mediterranean areas often used stone or stucco. Basically, the cheapest good material you can get.
Why one room, though? Heating. In England (because that's what I know best) houses were almost always heated with an open hearth in the middle of the cottage. This means that the heat would not get through to any separated rooms unless you had a second hearth there, which was expensive. This is the reason why richer people could afford to have more rooms and also fireplaces. A fireplace with a chimney causes some of the heat produced to be sucked out of the house which means that you're not getting all the available bang for your buck out of the kindling that you were using. If you had the money, you would could have two fireplaces or you could invest in braziers and bed warmers but most peasants, even the well off, didn't have those kinds of resources. From the houses that we have available from the end of the middle ages we still mostly see one, maybe two, room houses (and the second room wasn't necessarily a bedroom).
Generally the history of the home is one of an increasing growth and separation of rooms BUT this was only for the rich. Today, in the USA and Canada we have the luxury and space to have multi-bedroom homes available for the majority of people but this is quite a recent development. Single or double-room dwellings have been common, if not the norm, for most people for most of history. They are easy to build, cheaper to heat, don't take up as much material as something with more rooms and you could always add on to them if needed. Hall and Parlour homes, two room houses, continued to be popular all the way into the 20th century. Many places today still predominantly build one and two room (plus bathroom and kitchen) homes.