9.18.6.2.(1)

Intent 1:

To limit the probability:

• of an inadequate resistance to air and moisture transfer, or
• that the performance of polyethylene sheets will fall significantly below expectations.

This is to limit the probability of the ingress of moisture that is not under hydrostatic pressure from the ground, which could lead to deterioration, which could lead to compromised structural integrity of building components, which could lead to harm to persons.