patrick.net

basically they make you do it correctly with the permits at your own cost, and perhaps fine you.

but they don't want to be seen attacking their own citizens, so they're probably not going to come down super-hard.

You will have to bring it up to code. Don't know about fines, but I'm sure there will be some, not to mention that the permit costs can be exorbitant, not to mention the inspectors can be quite punitive as that is often their nature. The same as most government employees.

I doubt you'd run into a problem unless you try to sell... or if you have to have work/repairs/maintenance done later on the non-permitted area...

If you do it correctly, in my experience, the worst they do is have you submit a site plan and pay the permit fees, and subject your work to inspection

Tis better to ask for forgiveness, than to ask for permission

Depends on the city and the state and the county.

Depends on a county just like Dungeness said. In LA for example, if it's not up to fire or earthquake code, expect to move out and lose residential permit on entire property. The city doesn't screw around with this stuff here. Other places might be more lenient.

For non life threatening crap, compliance fee is about $400 otherwise if it's something that can be corrected, and you get about 15 days to do it. Or pay another $400. They might force you to turn it back into original state if you did something very wrong and can't fix it in time. For example you build something that is too close to neighbors property, city will force you to tear it down.

Sort of but they call it the Uniform Building Code for a reason.

If you are in Calif with the disclosure laws, when you sell is when you will have a problem.

I've done two Reno's involving structural, plumbing, and electrical. Got permits for both. Retroactively trying to get a permit would be a nightmare. Putting in a new electric fixture or something would be no problem to do later, and a permit wouldn't be worth the hassle. If the change is major, it is probably hard to get the permit later. If the change is minor or just surfaces, don't worry. If it's something with HVAC, wood stove, or other major appliance, get a permit or you could have insurance issues.