A.Henri de Marne responds: The system the specialty contractor describes is commonly used by residential water-proofers. The injected coating, which is probably bentonite, is generally effective for only a short time, and is probably not worth the added expense. But the interior drain will remove the bulk of the water, and will last a long time, if done properly.
I have used an interior perimeter drain connected to a sump pump a number of times. It is often the best choice, depending on the house site. In general, I choose an interior drain when:
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