I have several chimneys in my pre-1848 house. They all need work, and I want all of them to be functional down the road. One in particular is a problem right now:

The roof flashing has been leaking water down its side for no telling how long. The house was unoccupied except the occasional weekend renovation for the past half century. For the most part the chimney looks great, up in the space above the bedroom ceiling (which we ripped out as it was drop down tile) it seems pretty smooth and solid, but the POs built a 'closet' onto the face of the chimney, then PLASTERED the side of the chimney (and not correctly) to make it match the sheetrock they built the closet out of. So the water has been collecting in the plaster, deteriorating the chimney (both brick and mortar) beneath where the plaster was.

The mason I had out wants to rip the whole thing down which is an absolute NO-GO. I would think the area that needs it could be re-pointed for structural improvement and to save the original chimney; and an insulated liner run inside to deal with containment of gases associated with using the chimney down the road.

Is this a reasonable expectation? I am way out in the middle of nowhere and there aren't a whole lot of 'restoration' resources for me. Most local labor is handy-man style, which is fine for some things but this seems like a really important thing to get absolutely right.

Also, the place that is deteriorated is about three feet high and when I say deteriorated I mean the lime is completely gone leaving nothing but wet sand behind. I can scoop it out with my fingers. Is that too far gone for repointing? I don't want to see the whole chimney collapse when the sand is removed in this area. How should I expect this to be done safely?