Where do the unit shear values come from?

They are the nominal unit shear capacities tabulated in AWC SDPWS Table 4.3A for blocked wood structural panel shear walls on Douglas-Fir-Larch or Southern Pine framing. Each value depends on panel thickness, nail size, and edge nail spacing.

How do I convert nominal shear to a design value?

For allowable stress design divide the nominal unit shear by 2.0, and for load and resistance factor design multiply by the resistance factor of 0.80. The tool applies whichever method you select before computing wall capacity.

Why does tighter nail spacing add so much capacity?

Edge nails transfer shear between the panel and the framing. Closer spacing at panel edges means more fasteners sharing the load, so going from 6 inch to 2 inch spacing can more than double the unit shear capacity.

Is panel nailing the only thing that limits a shear wall?

No. Hold-down anchors that resist overturning, the wall aspect ratio of height to length, and the sill-plate attachment to the foundation all cap real capacity. This tool covers the panel unit shear; verify the other limits separately.

Does this apply to unblocked walls?

The stored values are for blocked walls, where panel edges land on framing or blocking. Unblocked walls have lower capacity and require separate adjustment factors, so use a blocked configuration for these numbers to apply.

Wood Shear Wall Capacity Calculator

A wood shear wall resists lateral wind and seismic force through its sheathing nails, and the code gives those capacities in a single table. This tool reads the right value from AWC SDPWS Table 4.3A for your panel and nailing, converts it to an ASD or LRFD design value, and checks the wall against your story shear.

How it works

The nominal unit shear is selected from the table by panel-and-nail combination and edge nail spacing, then reduced to a design value and scaled by length:

v_nominal = SDPWS 4.3A [panel/nail][edge spacing]   (plf)
v_design  = v_nominal / 2.0           (ASD)
          = v_nominal × 0.80          (LRFD)
capacity  = v_design × wall length    (lbf)
check     = applied story shear ≤ capacity

Closer edge nailing and thicker panels raise the nominal value sharply, which is why tightening the edge spacing from 6 to 2 inches is the usual first move when a wall is overstressed.

Tips and notes

These capacities assume a blocked wall — every panel edge backed by framing or blocking — on relatively dense DF-L or Southern Pine framing. The panel shear is rarely the only limit: overturning is resisted by hold-down anchors, slender walls are penalized by the height-to-length aspect ratio, and the load still has to pass through the sill plate into the foundation. Confirm those load-path elements before trusting the wall, and remember that increasing nail size or panel thickness is often cheaper than adding wall length.