hoping I can get some advice on this. We have a c. 1876 house in CT that has a half brick (above grade, mostly), half fieldstone (below grade) foundation. We are planning on repointing it, using lime mortar from limeworks. I'll post pics at the bottom.
Someone had mentioned they had concerns about mortaring a foundation that had never had mortar before. In the majority of the foundation it really seems like mortar was never there. There is mortar in a few places, but these look to me like later repairs, not necessarily original (see third picture-the top is mortarted to the side of where they knocked a portion of the foundation out for an addition and where it looks like they filled in a window). There's just dirt coming through most of the stones. There is occasional dampness in some sections but never actual liquid water that I've seen. It does get humid down there but the dehumidifier brings it down to about 40%.
Is anyone on here aware of any issues repointing (or perhaps mortaring for the first time) may cause? I had thought by using lime mortar I would be okay regarding any moisture that needs to get through and not do any harm, but now I'm nervous! We really just want to close up any holes for animals and keep the dirt from falling through. I have no desire to make the basement watertight and know that it never will be.
Will mortaring the stones keep the dirt that is currently coming through stuck behind it and increase pressure? I had been thinking of leaving the bottom layer or two unpointed as a route for water or dirt to escape if it needed. Will it be totally fine?
Thanks so much for any help! This foundation has been here for 150 years and I'd hate to be the one to do something detrimental to it!