Build foundations generous enough for somebody else to add another floor.

A foundation built to hold exactly one building is a limitation dressed as efficiency. Generosity in the base costs more at the start and pays back every time someone wants to add something you did not imagine. It is the difference between finishing a thing and starting one.

When you build, ask what someone would need in order to extend this rather than replace it. Leave that capacity in even if you never use it yourself. The extra floor is not your job, but making it possible is.