To limit the probability that valley flashing, in combination with the top layer required by Sentence 9.26.4.3.(6), will be unable to resist structural and environmental loads (such as those imposed by foot traffic, UV exposure, snow accumulation, ice damming, rain and freeze-thaw cycling), which could lead to the displacement of roofing.
This is to limit the probability of:
This is to limit the probability of harm to persons.