Depends on how extensive the growth is and how structurally stable the thing is in the first place. But expect major problems on the decades-timescale.

> "and in an invisible way?"

Yes. This is the main problem with allowing unconstrained plant growth near/in/under structures - the degree of structural compromise is hard to assess (especially without spending a lot of $$$), and failure can be sudden. You're not gonna get as much warning as you'd want.

In the US it's a popular look to have vines growing against brick walls. They're beautiful but often hazardous for structural safety, especially if not proactively maintained and constantly monitored (which is $$$!)

[edit] I think overall the focus on the "pleasantly ramshackle" aesthetics of the shack misses the forest for the trees. There's a lot of daylight between "permit small businesses in possibly unsafe structures" and "western status quo norms for business licensure".

I think something Japan gets done really well is making it easy and inexpensive to run businesses, especially hobby businesses. There are a ton of policies that encourage this outcome, and we can and should adopt entire rafts of them without changing existing regs about the physical structural stability of said businesses ;)

Short enough to kill you or your direct descendants. These things can look fine for years and then collapse in one day.

> and in an invisible way?

Makes no difference how visible it is if you don’t understand the risk and do nothing until something happens. And the longer you wait, the harder it will be to remedy.

> I believe buildings are seen as more temporary in japan than in the west

I’m not talking about Japan, I’m addressing the general point.