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The table below indicates where to find the sheathing bending strength values to resist component and cladding wind loads on exterior surfaces of the building for the following materials
from the
Structural Panels, Plywood siding |
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5/16” thickness |
WFCM 95* Table 3A |
All other sizes, spacings |
SDPWS Table 3.2.1 |
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Fiberboard |
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All sizes |
SDPWS Table 3.2.1 |
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Lumber Sheathing |
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All orientations, 3/4" |
WFCM 01 Table 3A |
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Gypsum Wallboard and Plaster |
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All materials |
Not included |
Values from WFCM
Values for lumber sheathing are taken from the 2001 (and later) WFCM , as SDPWS does not list these values. Values for 5/16” sheathing are taken from the 1995 WFCM as they are in neither the SDPWS nor the 2001 WFCM.
Wind Load Duration Factor
The SDPWS values incorporate a wind load duration value of 1.6, so Shearwalls does not apply a further load duration factor. WFCM does not include the load duration factor, so lumber sheathing values from the WFCM are multiplied by the 1.4 factor given in WFCM table 4A.
ASD Design Factor
The values are divided by 1.6 for ASD design in Shearwalls, in accordance with SDPWS 3.2.1
Continuous Support Assumption
The WFCM values were based upon the assumption of three span stud support, the SDPWS is based on two spans. SDPWS C3.2 says that the reason for this change is that two span conditions often exist at end zones where the forces are highest.
The program allows you to select which assumption you prefer based on the characteristics of your building, via 2-span and 3-span buttons in the Out-of-plane sheathing assumption data group in the Design settings. The span assumption appears in the legend below the Components and Cladding by Shear Line table.
The default value for new files is 2-span, in accordance with SDPWS.
When 3-span is selected, the factored tabulated values are multiplied by 1.25.