If you are aware that guests will likely be late, then make sure on the invitation says 15 minutes earlier than the actual ceremony start time.
When guests are late and if you delay the starting time, then there may be less time afterwards for photos, etc.
For example, if you want to begin your ceremony at 2:00 PM, then put on your wedding invitation for 1:45 PM.
Making it 30 minutes earlier may sound better, but you do not want people standing outside if the doors are locked!