For the 2021 version of APA's Load Span Tables, I noticed that the uniform load (PSF) values for plywood sheathing have different values than the Structural I sheathing (specifically for the Perpendicular to Supports Strength Axis).
The only issue is, when referring to the 2020 APA Panel Design Specification, it shows the "Structural I Multiplier" should be set at 1.0 for all scenarios where stress is Parallel to the Strength Axis. There are also different values for the number of plies, but nothing ties the number of plies to a Structural I panel.
Example:
From Table 9 for a 40/20 Span Rating, the FbS = 625
Considering an on-center spacing, L=30" and using the formula: 120 x FbS/L² = 120 x 625/30² = 83 PSF (This matches Table 1a)
However, Table 1b shows 100 PSF for that same condition (Note the Structural I Multiplier in Table 9 is 1.0)
This corresponds to a 5-ply panel from Table 9.
Are we to assume that whenever a Structural I panel is specified, we should calculate it based on the maximum number of plies available? I don't see this requirement anywhere in the documents.
2021 APA Load Span Tables:
2020 APA Panel Design Specification:
The only issue is, when referring to the 2020 APA Panel Design Specification, it shows the "Structural I Multiplier" should be set at 1.0 for all scenarios where stress is Parallel to the Strength Axis. There are also different values for the number of plies, but nothing ties the number of plies to a Structural I panel.
Example:
From Table 9 for a 40/20 Span Rating, the FbS = 625
Considering an on-center spacing, L=30" and using the formula: 120 x FbS/L² = 120 x 625/30² = 83 PSF (This matches Table 1a)
However, Table 1b shows 100 PSF for that same condition (Note the Structural I Multiplier in Table 9 is 1.0)
This corresponds to a 5-ply panel from Table 9.
Are we to assume that whenever a Structural I panel is specified, we should calculate it based on the maximum number of plies available? I don't see this requirement anywhere in the documents.
2021 APA Load Span Tables:
2020 APA Panel Design Specification: