I recent bought a house with a detached garage, made of old concrete (high aggregate content) reinforced with steel rods and set into a hill. Built in 1938 or so; no waterproofing.
Now that Boston has turned into a rain-forest, water is seeping / leeching through the walls of the garage, making the whole thing very damp and smelly. There are no obvious drips, but the bottom 3-4 feet of concrete is discolored and damp, and there are patches of dampness on the (newer) floor.
The concrete is degrading, and I was thinking of parging over it with new concrete to smooth the walls, but I want to address the leaking first. Or would a parge coat help? What else can I do to seal up the concrete, short of digging up the foundation (15' of dirt with a garden on top!) and painting the outside surface?