Alligatoring describes a particular way in which exterior paint can fail. Alligatored paint on the exterior of a house is caused by heavily built-up layers of paint that become brittle. Over time, successive layers of paint dry out, and small cracks in the paint layers (called crazing) develop. These breaks in the protective paint coating allow moisture to penetrate through to the underlying wood, which then swells with moisture, causing the paint layers above to crack further. Larger stress fractures in the paint film develop and the paint surface cracks into small, uneven boxes that resemble alligator hide.