Minimum grades for visually graded lumber used as:

• loadbearing and non-loadbearing framing members in stud wall framing,
• loadbearing and non-loadbearing framing in plank frame construction,
• framing for posts and beams, and
• roof and wall sheathing, and subflooring.

This applies to buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9].

To limit the probability that inappropriate grades of visually graded lumber will be used, which could lead to compromised structural integrity of the visually graded lumber or of elements supported by the visually graded lumber, which could lead to excessive movement, deformation or failure under expected lateral, gravity or wind uplift loads.

Where lumber supports or is used in an environmental separator, this is to limit the probability of compromised performance of the building envelope, which could lead to:

• condensation,
• precipitation ingress, or
• compromised thermal performance of components intended to provide resistance to heat transfer.

This is to limit the probability of:

• an inadequate control of indoor air and surface temperatures, drafts, relative humidity, or water accumulation,
• the generation of pollutants from biological growth or from materials that become unstable on wetting, or
• deterioration, which could lead to further compromised integrity of environmental separators.

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.