Re: "Maybe it could be stretched to include the previously mentioned
chicken coop?"

Interesting.

My neighbor in Croton-on-Hudson, NY has a delapidated chicken coop of
such vintage on the otherwise vacant property next door, and has not
torn it down since he knows he would never be permitted to build one
today, and is hedging himself for future repairs.  But if he can't
keep chickens, how does the "still be used as a barn after the
restoration" rule apply?  And if you take the tax break, how long
must you maintain the coop?  This is getting a bit messy, isn't it.

Actually, my neighbor has a second old structure on the property,
which was and still is used as a garage.  Is that a barn for cars?

--Rev. Jim