While my methods aren't necessarily cheap, no homeowner has called me back owing to water infiltration. I start with an excavation to ~18" below the footer, wide enough for me to work. I recover the refrigerant and disconnect condensing units. Pressure washing of the exposed wall area which is below grade prepares it for Thoro® Foundation Coating, applied in two coats with a wide brush. Then the bottom of the trench is stoned-3/4" modified is fine. A transit is used to verify elevation and that the stone bed is pitched for proper drainage. 6 mil poly sheeting is taped to the wall, and draped over the coated foundation and stone. Panels of 2" expanded foam insulation board are placed against the poly sheeting. Two runs of corrugated plastic piping are placed in the excavation. One is solid, and using wyes, branches extend upwards to accept water from downspouts. The second is slotted to collect water at the footer level. Both pipe runs are covered with more stone, up to ~18" from finish grade. A layer of geotextile cloth is then placed atop the stone, and the excavation is backfilled and finish graded, seeded, and strawed. This can be done in a one way run, or in a horseshoe, depending on site elevations. If permissible without creating slip hazards, the piping discharges at grade, away from sidewalks and driveways. Otherwise, I dig a pit about the size of a Geo Metro, end the piping there, and fill with ballast stone, creating a dry well for site containment of water. If basement windows are involved, a length of 2" PVC pipe with a perforated cap is placed at each window well to lead any ground water down to the drainage bed. Depending on site factors, it costs between $5 and $10K, but like I said at the beginning, it works.
