As an addendum, you can ask Op level staff (Kusorai, AnonymousSoFar, WindRider739, aDeadlyFish) to enable the protection as well.
External: Home Protection Program, Update by Dr. Cossack
It is possible for any players on the server to have their creations protected against unexpected modifications (or griefs).
With the Home Protection Program, your buildings can be set so that only you, or a list of authorized people, will be able to make any changes within a given area. This means that random people won't be able to place block, plant signs or burrow through your walls to find their way inside. This is used to complement the locked doors mecanism that you already have access to. You can also define friends to be able to work on your home even after it's locked.
To get this protection, meet me (Dr. Cossack) in-game and I'll take care of it!