I am looking into which cement to use to repoint our old house (built ~1900) stone basement. I found conflicting advice, some suggesting type N or type S is fine, but some sources suggest that Portland cement is not compatible with hydraulic lime cement that was likely used in the original construction.
I am fairly certain the original is lime cement as it is currently crumbling on the inside in the manner typically described of this type of material. It seems that hydraulic lime cement is typically used to restore old masonry, but has multiple downsides, as it is more expensive and complicated to mix, has lower water and stress resistance, and is likely to need repair sooner.
At the same time if I resort to using one of the Portland cement mixes I am afraid it will impact the existing cement left deeper in the stone foundation, causing cracks and instability. The basement has some water leakage so I am looking to waterproof it as best as possible, but without affecting structural integrity of the foundation.
Any advice on whether type S would work ok with existing cement or whether Hydraulic Lime cement is the way to go?
