That being said, things that are cheap to repair and cheap to rebuild like drying racks can easily be built off claim in a pinch... You'll notice them start to get a slightly red hue when they're getting down near 50% or so, and you can attempt to repair them and it won't let you if they're already 100%.
Don't do this with walls though, stone hedges are pretty cheap to build but they burn through granite like no tomorrow to repair (1 granite every 2% or maybe slightly more). I was a bit lazy when getting my settlement going since Popham is pretty dead and there don't seem to be many raiders so I built my walls before expanding my claim out to fully encapsulate them and had to pay many granite boulders for my foolishness afterwards.
Note that mines are a weird case... They're not technically a claim even if you claim the mine entrance, but nothing decays in them either. If you have a mine with a lot of space emptied out consider putting buildings in there to save surface space, but the danger is that if raiders are able to break into your mine then they're free to destroy/loot everything without worrying about further brazier fire. Not everything can be built in a mine but most things, the list at the bottom of this page is mostly up to date but missing a few things:
http://salemwiki.info/index.php/Mine_Entrance
