The stile and rail door unit was installed only a couple of years ago. Manufacturer's recommendations and instructions were followed to the letter. The door swings inward and there is no storm door attached to the unit. A pre-cast concrete stoop rests against the house beneath the entrance. Unfortunately, variations of this theme are common.
Several conditions lead to the failures described.
First of all, reliable overhead protection should be part of the entryway design. But more important than convenience, overhead protection eliminates splashback. Rain or roof run-off splashes vigorously off masonry surfaces like brick walkways and concrete steps, wetting adjacent wall surfaces. North-facing walls are particularly prone to decay. They remain wet longer than other walls.