My home has a poured concrete foundation with 2 rows of concrete block added to the top. The seam between the concrete and block appears to be at grade. Water is leaking at various spots along a 25 foot section of this seam. A drainage fellow said that since the block and foundation come together at grade, you cannot use a membrane to fix it from the outside because the top will be exposed to light and elements, ultimately causing it to fail. He suggests busting out a 6-8 inch section of the concrete floor in the basement, follow it along the 25 feet of wall, putting in drainage tile, and allowing water to continue entering, but now be directed in a safe manner.
Answer:
At a lesser cost in both money and convenience, you could introduce 2" rigid foam insulation over the sheet (and up to the siding of the house) your contractor suggested. The rigid foam insulation can then be capped to keep water from running in behind it. The foam could then be parged. These are all products that are on the market. You might talk to someone who makes his living working on foundation walls.
