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The following parameters can be input for the sheathing applied to either or both sides of a shear wall in Wall Input View.
Sheathing Material
Shearwalls allows for plywood sheathing, plywood siding, fiberboard, gypsum wallboard, lath and plaster, and lumber sheathing. Refer to the topics under Provisions by Sheathing Material Type for detailed tables showing the choices of wall material available in Shearwalls.
Fiberboard and gypsum-based materials are not available if wet service conditions are selected in the design settings.
Changing the material refreshes the choices for all other inputs in the dialog.
Sheathing Thickness
The program provides a list of standard thicknesses for each sheathing materials from SDPWS tables 3.2.1, 4.3A-B, and C4.2.2B. You can enter a thickness yourself and the program will use the tabulated design value for the closest thickness less than the one you selected, so this input can be considered a minimum thickness. However, plywood and GWB are not manufactured in other thicknesses, so there is little need to enter a thickness other than one in the list.
Sheathing thickness can be also be "unknown", for which Shearwalls will determine the minimum allowable thickness that resists the applied load.
Changing the thickness refreshes the choices for span rating and nail size.
Orientation
Direction of long side of panel. For structural wood panels, this is vertical or horizontal. The orientation primarily affects wind component and cladding out-of-plane bending design, but there are certain exceptions for shear wall strengths that depend on orientation. For lumber siding, the orientation can also be diagonal or double-diagonal, and orientation affects shear strength.
Span Rating
The span rating is linked to the sheathing thickness according to SDPWS Table C4.2.2C. The program includes both the primary and alternative span ratings for each thickness, defaulting to the primary. The value for shear stiffness GvTv from table C4.2.2A is based on selected span rating, not the selected thickness.
Plies
Number of plywood plies used to select shear stiffness Gvtv value for deflection design from SDPWS Table C4.2.2.2A
OSB
A checkbox indicates whether the structural material chosen is OSB, so that it uses the shear stiffness values Gvtv from SDPWS Table C4.2.2.2A for OSB.
OSB is not allowed if wet service conditions have been selected in the Design settings.
Blocking
This check box indicates whether the sheathing panel edges on the selected side or sides are nailed to blocking. Note that vertically oriented panels are still considered to be unblocked unless they are staggered such that there are horizontal seams to be blocked.
An unblocked factor is applied to shear strength and deflection calculations for unblocked structural wood panels. Gypsum wallboard has different shear design values depending on whether it is blocked or unblocked.
Gypsum Wallboard Underlay
You can specify either 1/2" or 5/8" gypsum underlay beneath a wood structural panel. The design capacities in SDPWS Table 4.3B for wood panels over gypsum overlay are the same as the ones in Table 4.3A, except that a different combination of nail length and sheathing thickness yields the same value, due to the effect of the underlay on penetration. Furthermore, there are fewer such combinations available with gypsum underlay present. .