I am considering purchasing an older home. It has a stone foundation that has recently been parged. During my last trip to the home, I noticed some standing water on the floor (not close to the walls at all) and some discoloration on one of the walls. I received a quote from a waterproofing company that would put in an interior french drain with holes into the walls to help release trapped water. I am wondering A) how important is it to drill into the walls (will not doing that hurt the integrity of the foundation in the longrun) and B) if I can remove all standing water by improving grading and gutter spouts (both are pretty bad now), should I still consider the system that allows water to be released from the walls? An exterior drain system would be prohibitively expensive and I worry that it would cause more problems (when removing the soil support for the foundation to install the system) than it would fix. Any help would be really appreciated! I love this house and want to make sure that I am doing the right thing.