A very small amount of saturated groundwater that enters basements and crawlspaces does so by soaking through the foundation wall itself.

In the case of basements, the groundwater most often enters at the cold joint, which is the air space between the floor of the basement, and the foundation wall. This is because the basement foundation walls are first poured, and then the floor is floated, which creates an air space between the wall and the floor of the basement.

Hydrostatic pressure caused by the groundwater saturation forces the groundwater through the cold joint.

In the case of the crawlspace, the groundwater most often enters below the foundation footing.

The groundwater soaks down the foundation wall to below the footing, and is pushed by the hydrostatic pressure into the air space that is the crawlspace.

Groundwater around a basement will generally soak all the way to the basement floor in nearly every case, except the case where there are large cracks or holes in the foundation wall itself. If that is the case, they should be filled and repaired by a drainage contractor-mason.

Installation of membranes with tar, only enhance the process that is naturally occuring. That is to say, the groundwater just continues to soak along the outside of the foundation wall with the membrane, just as it would without the tar and membrane.

In fact, if some of the groundwater gets trapped behind the membrane, the foundation wall may stay wet back there and not dry out, like a foundation wall without a membrane would in dry weather.

Prevention of groundwater saturation, and removal of groundwater with hand excavated french drains will dry out the foundation wall all the way to the base of the basement floor.

Without removal of the groundwater when it is raining, your groundwater problem will be as bad or worse, even after installing a membrane.

If you install hand excavated french drains properly, you will most often not need sump pumps or membranes, whether they are outside, or inside the crawlspace or basement. Venting the groundwater faster that it can soak in is your primary objective.