To permit or not to permit construction?

[Jessica Chow]

Hello BP fam! I own a SFH in Los Angeles and am thinking of making some upgrades- 1) opening up a retaining wall that leads into the backyard and install a sliding glass door 2) adding a 10x12 wood floating deck My questions are: 1) How would I calculate the increase in value for these upgrades? 2) Does doing this type of upgrade without a permit dissuade future buyers?