Damp refinished basement

[Tim McCahill]

The ground floor of my duplex apartment is below-grade and has experienced water infiltration. I only recently bought the property and have repaired the leaks I can identify, but one appears to be coming from the outside entryway of a neighboring attached building - essentially, the entryway is badly graded, causing water to pond in the area where the building meets mine and penetrate my basement. It's uncertain whether this area will be repaired and I'm looking for alternative solutions, like waterproofing the party wall from inside my basement. Has anyone done this before? What were the results? Thanks.