The topic of permits is always fun discussion with homeowners. I can't count the number of times I have people say "why do I need a permit from the City, i'm just doing a simple "whatever".
Well the easy answer is anything that involves electrical, plumbing, structural and mechanical may need a permit. It is easy to obtain a list from the City website to verify what needs a permit.
So the next question - How's the City going to even know what I did. They probably never will unless someone alerts them to the change. Who would do that? Do you have any neighbors who you don't get along with? Or if your house is on the market a potential buyer.
So what happens if the City finds out? They will check out whatever was done, determine if it is to code, if not (depending on what was done) require modifications or remove it. And of, course you will need to get the permit.
If you do plan to sell your home and there is some un-permitted work in the house, you must disclose this to your real estate agent and the buyer. If the buyer is okay with the un-permitted work and is willing to accept any financial burdens in the future (if there are any), then you are good to go.
My advice, get permits. Better to be safe than sorry!