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However, tar foundation coating is not a water proofing compound, it is a vapor proofing compound and over time, if your french drain fails, you could have water penetration into your basement.
DryLok will serve as a water and vapor barrier but should not be used as your first line of defense in this regard.
Water and vapor proofing should always be done on the outside of the foundation, but it is not always practical or economical to do so. Especially after a home has been completed.
Foam actually has a high permeablity rating.
Permeability is the quality of a material to allow water or water vapor to pass.
The only way to prevent water from entering your blaock is to apply a specialty coating to the outside of the foundation or a rubber membrane around the outside of the foundation.
This will not keep the water out but offers a way to catch it before it causes you harm. Be aware of humidity levels before and after any work. It is possible to stop the water but increase the humidity. High humidity can lead to mold.
Hope this helps,