The Foundation/Drainage System
Finally, supporting the house is the basic function of the foundation, but it is an important part of the weather envelope as well because it controls proper drainage from above. Also, as rain water drips off the water table board or the roof eaves above, it hits the ground, and splashes back against the above-ground portion of the foundation. When the foundation's stones or bricks are tightly connected with mortar, the water flows down the face of the foundation, not into the wall. Of course, you also need to grade the ground next to the building so it slopes away from the foundation. That way, rain water will be diverted from the foundation walls into the yard beyond.