Sentence 9.26.6.1.(1)

Intent 1:

To limit the probability of:

• moisture-permeable underlay absorbing and retaining water, or
• water- and vapour-impermeable underlay providing a surface where condensation can accumulate in roof spaces.

This is to limit the probability of long-term wetting of roof decking or sheathing, which could lead to damage to roofing, which could lead to:

• condensation, or
• precipitation or meltwater ingress.

This is to limit the probability of deterioration, which could lead to the structural failure of roofs or assemblies protected by roofs, which could lead to harm to persons.