http://www.askthebuilder.com/B10_Forces_Harmful_to_House_Foundation_Footers.shtml

"gravity,soil swelling,soil collapse,frost heaving,hydrostatic pressure etc...can cause serious harm to footers and foundations"

"many soils absorb vast quantities of water and this added water,combined with the soil,pushes against your foundation wall.This force is commonly referred to as Hydrostatic Pressure"

And so, what does NOT absorb vast quantities of water? What applies the LEAST lateral pressure against basement walls?

.....read 6th para....

http://www.yodergroup.com/concrete.asp

"we firmly believe a foundation should be backfilled with washed gravel(NOT dirt) from the basement floor level all the way UP to within 2-3" of the finished grade outside..."......."this is especially important, if not Critical, with soils having high clay content.Secondly this type of DRAINAGE Prevents trapped water and saturated soil next to foundation from building up horizontal hydrostatic pressure AGAINST the Wall. This PRESSURE will crack walls, cause Leaks, and in a worst case collapse the wall inward"

http://www.bobvila.com/HowTo_Library/Why_Foundations_Fail-Foundation-A2095.html

"coarse grained,well drained soils like sand and gravel apply the LEAST lateral load"

http://www.askthebuilder.com/015_Exterior_Foundation_Wall_Waterproofing.shtml

"Many, many consumers THINK they have waterproofed basements, when in fact they simply have been damproofed"...."use plenty of (three feet minimum)washed gravel over drain tile"

http://www.askthebuilder.com/B15_Waterproof_Foundation_and_Damp_Proofing.shtml

"thousands of homeowners THINK they have a waterproofed foundation when in fact they do NOT"

http://www.askthebuilder.com/NH058_-_Waterproofing_Foundations.shtml

"there is a Significant Difference between damproofing and Waterproofing"

http://www.al-home-inspections.com/news-articles/article-4.html