Sentence 9.25.3.3.(2)

Intent 1:

To limit the probability of openings in the joints of flexible sheet material (such as polyethylene) under in-service tensile stresses, which could lead to a loss of airtightness.

This is to limit the probability of:

• excessive airborne vapour transfer from interior above ground and exterior below ground, or
• precipitation ingress due to air pressure differences.

This is to limit the probability of deterioration, which could lead to compromised structural integrity of assemblies acting as or protected by environmental separators, which could lead to harm to persons.