Permitting an existing ADU

[Casey Boerger]

I own a house in north pierce county WA with a mother-in-law inside a detached garage. The mother-in-law was there when I bought the property but was not permitted when built. I am wondering what issues I may run into trying to get the MIT permitted. The construction looks sound but I don’t know the codes. I also have done some structural upgrades to the foundation of the primary house where I live and I did not get permits for that work. Will trying for a permit open up a can of worms for me? Where can I find more about this process?

Thank you for any information.