Intent 1:
To limit the probability that the shingle fastening
will be unable to resist uplift forces from wind, vibration and gravity,
which could lead to the displacement of shingles, which could lead
to:
- water penetrating directly to roof decking or sheathing,
or
- compromised thermal performance of components intended
to provide resistance to heat transfer.
This is to limit the probability of:
- an inadequate control of relative humidity, temperatures
of interior spaces or water accumulation,
- the generation of pollutants from biological growth
or from materials that become unstable on wetting, or
- deterioration, which could lead to compromised integrity
of roofs or walls or of assemblies protected by roofs or walls.
This is to limit the probability of:
- negative effects on the air quality of indoor spaces,
- the inadequate thermal comfort of persons, and
- contact with moisture.
This is to limit the probability of harm to persons.
Intent 2:
To expand the application of Sentences 9.26.7.4.(1) and (2) to include constructions where relatively
narrow shingles, or shingles that do not rely solely on fasteners,
are used.