Did you know that there is a big difference in exterior foundation waterproofing treatments? You probably think that your new home foundation has been waterproofed. You saw your contractor spray on black sealer and believe you are in good shape. What you don't know is that fewer than 1 in 50 houses in the your area's housing market have waterproofed foundations. Most are only damproofed.

Before you build, the ground is hard and packed, especially if it is clay. There is little room for water to seep into the soil. When a house is being constructed, a portion of the ground is scooped out to build the foundation. This creates a large "bowl" in the ground. The foundation is placed in the "bowl" and the dirt that was dug out is pushed back up against the foundation. This dirt is now loose and mixed with air. This "fluffed up" dirt is now sitting in a bowl of hard dirt. It can take many years for the disturbed dirt to compact to the same density as the dirt forming the bowl. In many cases, it may never compact to the same density. Water naturally flows toward less dense soil which means your house is actually built in a bowl of water. This is known as the Clay Bowl Effect.

For more information, read this damp proofing article and this article on Clay Bowl Effect.