Answer: The easiest way for water to get into structures is through windows, doors and other areas where no water protective building components are installed.
When water gets into building structures it creates a suitable environment for the development of other serious problems – such as mold, dry rot and decay. It is one of the most common causes of building repairs and can be costly.
To minimize the possibility of water entry, all critical detail areas should be flashed (flashing is a piece of material used to cover and protect certain joints and angles especially against leakage) using the appropriate flashing materials and following the proper installation techniques. Right now I recommend using Grace Vycor flashing for doors and windows or Typar. They are good products and If installed correctly will keep your windows and doors water proof.