Below photo courtesy @kiwilostie
It seems that the rock walls are original, but rock extending along the roofline was added by the LOST team. (Or perhaps they temporarily removed the thatch to expose the extra rock, its hard to say.)
@Lottery_Ticket stood in the doorway for several minutes deep in thought, perhaps imagining a rendezvous with the returning Spaniard. If only 150 years didn't separate the two! (Not to mention that pesky difference between reality and fiction.)
There is actually a second cottage in the same location sitting a little to the left of the one that served as Richard's home, though it doesn't get any screen time.