As a matter of geological record, the Earth's magnetic field has undergone numerous reversals of polarity. We can see this in the magnetic patterns found in volcanic rocks, especially those recovered from the ocean floors. In the last 10 million years, there have been, on average, 4 or 5 reversals per million years.
When coming to building something, some materials are more vulnerable to water and can wear away easier. Some can keep the water in, so depending on the material, the water quality can be better sustained.