If this has wood on the concrete -- wall base plates, etc. -- you want to be sure to seal at those joints and the wood. Garages generally have a row of block, this may not. Often smaller buildings will bring the metal pins right up from the slab.
If the barn is truly an older barn, you may have block up at perimeters...and even a drain trough when I built my barn, I had foundation and block up, wood walls onto that. But I left dirt floors, except tack room. Concrete there. All has pro/con.