There are several offices for the LA Building and Safety, here is their web site to find out which one is closest to you.
You can try calling 1-213-473-3231 however, in my experience it takes a long time to get through all the automation.
You can go to the department of building and safety and get the information over the counter. They are very helpful... make sure you have a rough drawing of what the garage looks like and the dimensions.
Just a sketch.