SDPWS Footnote 3: Species-Specific Gravity Adjustment per NDS Table 12.3.3A

Example

An 8×8 ft shear wall has 7/16 in. OSB and 8d common nails at 6 in. spacing. Framing is Spruce-Pine-Fir (G = 0.42), not Douglas-Fir-Larch or Southern Pine. Wind load = 1,800 lb. SDPWS Footnote 3 requires Vn × [1-(0.5-G)]. Check capacity with this adjustment.

How StructSuite solves this

StructSuite applies SDPWS Table 4.3A Footnote 3: Va = Vn × [1-(0.5-G)] when enabled. Species and G come from NDS Table 12.3.3A. Uses §4.1.4.2 for wind.

Steps

1. Step 1: Geometry & Configuration

   Design consideration: 8×8 ft residential wall. 1,800 lb = 225 plf unit shear—moderate. With SPF and 0.92 factor, need Va ≥ 225/0.92 ≈ 245 plf base. 7/16 at 6 in. typically suffices with Footnote 3 applied.

   In StructSuite: Open Step 1: Geometry & Configuration. In Height, h (ft) enter 8. In Length, b (ft) enter 8.

2. Step 3: Load Definition

   Design consideration: 1,800 lb wind for 8×8—typical single-story residential in moderate wind zone. Lower than DF-L region equivalent due to species adjustment; designer must account for local framing availability.

   In StructSuite: Open Step 3: Load Definition. Under Lateral force at top of shear wall line, in W — Wind (lb) enter 1800.

3. Step 2: Sheathing & Fasteners

   Design consideration: Table 4.3A Vn assumes Douglas Fir-Larch or Southern Pine (G ≈ 0.5). Lower-G species (SPF G=0.42, Hem-Fir 0.43, SP G=0.37) have weaker nail withdrawal; Footnote 3 reduces Va by factor [1−(0.5−G)]. SPF common in Northeast, Upper Midwest, Canada; DF-L in West. Factor 0.92 for SPF means ~8% capacity reduction—may need tighter nails or thicker panel.

   In StructSuite: Open Step 2: Sheathing & Fasteners. Select Wood Structural Panels - Sheathing, 7/16 in., 8d common, 6 in. spacing. Check Footnote 3 – Framing species other than Doug-Fir-Larch or Southern Pine. In Species (NDS Table 12.3.3A): select Spruce-Pine-Fir.

4. Step 5: Design Verification

   Design consideration: Adjusted Va = Vn × 0.92. Demand 225 plf must be ≤ Va. If marginal, options: tighter nail spacing (4 in. vs 6 in.), thicker panel, or specify DF-L/SP for critical walls. SPF acceptable for most residential; note on plans for framer.

   In StructSuite: Open Step 5: Design Verification. Confirm capacity check passes with adjusted Va [1-(0.5-0.42)] = 0.92.

Live design (pre-filled)

The form below is the real StructSuite module with example data loaded. Display only—values cannot be changed.