MB4 212b: Adding on to an Existing Wall to Halachically Enclose an Already Enclosed Large Yard (358:8-9)

If one has an existing enclosure around a קרפף can one simply add on to the existing wall in order to create an area that is מוקף לשם דירה?

Does planting trees in a קרפף enclosed for dwelling purposes negate its status as מוקף לשם דירה?