Hello!
In most places (at least in Germany) yards, patios or plots are not mapped, as it is not possible to divide the actual plots correctly. A mapper can just estimate where borders between plots lie. Official data from land registry offices can not be used in many places due to copyright issues.
What we do map though, is landuse=residential around a residential area (not around a single plot). That is regarded as sufficient.
If a significant garden is to be mapped, you can use https://wiki.openstreetmap.org/wiki/Tag:leisure%3Dgarden.
I hope this is of help…