In Santa Monica, if you want to find out what you can build on a particular lot, you will need to call the city. Specifically the planning department.
The phone number to the Planning Department is 310-458-8341. You also find it on the website smgov.net
You can also go to the public counter at the City Hall Room 111, and speak to the planner. The public counter is open 9-4pm on weekdays.
