Build a patio for rental

[Roman Romaniuk]

Hello everyone.

It might not be exact place to ask this type of question, but I really believe that a lot people from this forum have an experience with that, so you can help.

I have rental duplex with downtown view (located in San Diego), and back doors of this unit leads to balcony\patio with that view. Right now it's around 4 feet in depth, and you can go downstairs  and have some extra land there. It would make much more sense in this case to extend this patio\balcony all the way to the end of the land. But one of the renters moving out in a month, and other one in 2 month, so it would make even more sense to do it before getting new tenants. 

I'm wondering if I need/recommended  any permission from city, or since it's my land I can do it, anyway I already have balcony/patio. 

See picture for better understanding, and thank you in advance!