In the Pacific Northwest waterproofing problems are probably the #1 source of construction defect lawsuits. These lawsuits are bad for contractors and we all pay the price in the form of increased insurance rates which translate into higher construction costs for consumers.
The secret of waterproofing exterior walls is not some newfangled technology, but rather an evolutionary thinking about how we incorporate technologies that we have been using for decades. Academic tests and studies on the science of waterproofing exterior wall systems are freely available, yet many contractors still don’t follow these proven techniques.
The basic lessons from these studies are that we need to design for failure. That’s because it doesn’t matter if you use the latest and greatest Hardiplank cement board siding or cheap vinyl and aluminum siding, at some point the combination of wind, water, and gravity will cause water to get behind your wall. The secret question is, did you plan and design for the water that you’ve now got behind your siding? If you did, your wall system will have incorporated the following four elements:

Drainage plane – heavy felt building paper or housewrap
Drainage space – furring strips, stuccowrap + felt, two layer felt, or air gaps
Flashings – metal flashings to kick water out
Weep holes – openings to allow water to escape

If your wall system includes these four elements and it is well constructed, then you shouldn’t have any waterproofing problems.