Michael,

Your cracked limestone is interesting.  I would've thought rusting steel
would be the culprit, but you say it's OK. Is the building frame steel, or is
it concrete?  If concrete, the conc shrinks over time and that may be the
cause of your cracks.  If steel, be sure they clean, paint and flash the hell
out of the steel (Permabarrier) before you reset the stone.

Where on the bldg do the cracks appear? Corners, middle, parapets, spandrels,
everywhere?  Do you have cracked 4" stone next to uncracked 8" and 12."  ?

Tell us more.

Ralph