Is it better to waterproof a basement from the inside or outside?

It is far more effective to waterproof a basement from the outside through exterior waterproofing measures, such as installing drain tiles, excavating your soil and installing and cleaning gutters. 

The term “interior waterproofing” is something of a misnomer because any steps taken in the basement’s interior are more to mitigate damage from water that has already made it through the foundation. Water is best stopped at the source — that is, it is best stopped from ever entering the concrete foundation by exterior waterproofing. However, interior waterproofing is still an important and effective step to take.