sikkensuser

How would one go about installing counter flashing on a field stone chimney?. The mortar lines are irregularly staggered owing to the differently shaped and sided stones, making it difficult (maybe impossible?) to cut a groove in the mortar allowing the flashing to be tucked in.

CraigFL

This is difficult but if you want it to look professional you could use lead or copper flashings, malleable enough to conform to irregular mortar lines. You could also cut a straight line through mortar and stone too.

dmc@RCR

Lead is the way to go for flashing a fieldstone chimney. Malleable so you can follow the stone morter lines.
This webpage has a good example; Stone Chimney Flashing

itsreallyconc

we're professional & use hand grinders, diamond blades, levels, chalklines, & soapstone,,, usually lead or copper 'cause our work's not cheap,,, not much is impossible altho you may have to adapt