Prefabricated garage: earth-covered and walkable

Earth on top is not a problem, it just needs to be properly sealed against roots. My mother has that too, 5 duplex houses, and all the garages are next to each other with their backs to the street, then there is a soil embankment heaped on top. Only grass grows on it, no trees are allowed. And these are all just ordinary prefabricated garages. I would inquire directly with the garage manufacturer of my choice.