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Important Note – These are descriptions to changes implemented in WoodWorks Shearwalls for version 9 and may not reflect current behavior.
No changes are made to the shear design values from SDPWS 2005 to 2008 for these materials. Note that in Shearwalls the wind values are derived by multiplying the seismic values by 1.4, whereas in SDPWS they are multiplied by 1.4 then rounded to the nearest 5 plf, so there are slight discrepancies between the SDPWS values and those in the program.
In Version 8.x of the software, for the IBC design code option, the equation from IBC T 2306.4.1 Note was applied to the tabulated values to adjust for specific gravity. For the SDPWS option, the program was using the values in the specific gravity ranges from the original WFCM 2005, which can create significantly different capacities for some framing materials.
The program has changed to use the equation for specific gravity adjustment, which is the same equation as in SDPWS Table 4.3A note 3.
The exception that allows maximum intermediate framing (field) nail spacing for 24” stud spacing to be 12” rather than 6” has been removed for 5/16” panels. Previously the SDPWS listed 3/8” and 7/16” sizes for this exception, but now it is phrased thicker than 7/16”.
For Version 8, the IBC shear design values were the same values that were in the WFCM – 125 plf for ½” and 175 plf for 5/8” sheathing except that these values were not multiplied by 1.4 for wind design because this was not specified in IBC 2306.4.4. These values were independent of nail spacing choice but dependent on panel thickness. The SDPWS values from Table 3.4A were dependent on nail spacing but not on panel thickness, and are multiplied by 1.4 for wind design.
The program now implements the values in SDPWS Table 4.3A. The IBC table 2306.6 now includes identical values, and 2306.3 says to multiply by the 1.4 factor, so that the program now implements the identical IBC and SDPWS provisions.
To these values, a specific gravity factor was applied separately for IBC and SDPWS. Using IBC 2006 2306.4.1 Note a, it was based gravity ranges. and for SDPWS option, the equation for specific gravity factor from Table 4.3A note 3 was applied to the IBC/WFCM data.
The specific gravity adjustment from SDPWS Table 4.3A note 3 is now the only one applied. The IBC table 2306.3 now also includes the same equation for nailed fiberboard
The maximum stud spacing for gypsum sheathing board is restricted to 16”, the SDPWS limit. Previously, for the IBC selection, a spacing of 24” was allowed according to T2306.4.5.
No changes have been made to shear capacity for these materials except to add the choice of drywall screws, which have a lower capacity. Refer to .
Previously, for the IBC setting, only the Diagonal and Double Diagonal orientation choices were available, as these were the only ones listed in Table 2306.3.3 of the 2006 IBC. For the SPDWS choice, Horizontal and Vertical choices are also available. With the IBC choice eliminated, all sheathing orientations are available.
Previously, for the IBC choice, a specific gravity adjustment factor was applied based on the range of specific gravity for the framing material used. There is no longer a specific gravity factor for lumber sheathing, as SDPWS Table 4.3C does not include a factor for specific gravity of framing materials.
When different materials were combined on a wall, except for the combination of structural materials and gypsum wallboard for wind design, the choice of IBC meant that the strongest of the two sides was used as the shear capacity, as per IBC 2006 2305.3.9. The IBC option has been removed, and the program uses the rule from SDPWS 2008 4.3.3.3.2, that is, strongest or twice weakest.
The IBC provisions in Table 2306.4.1 had never been implemented for the IBC option. Now that similar provisions are in the SDPWS 2008 Table 4.3B,they have been implemented for Shearwalls 9. Refer to the following section for a complete description of the feature.
Otherwise, sheathing combination rules were the same for IBC and SDPWS, so no changes are made to the program by eliminating the IBC option.