Wood species or species group as listed in NDS Supplement Table 4A (e.g., 'DOUGLAS FIR-LARCH', 'SOUTHERN PINE', 'HEM-FIR'). Case-insensitive.

Lumber grade per NDS Table 4A (e.g., 'No. 1', 'No. 2', 'Select Structural', 'Stud'). Determines reference design values Fb, Ft, Fv, Fc, E.

Standard nominal lumber size (e.g., '2x8', '4x12', '6x6'). Converted internally to actual dimensions per NDS. Available: 2x4 through 6x12.

Clear span length of the beam in feet. Used for moment, shear, and deflection calculations. Typical: 8-20 ft for floor joists, 10-30 ft for beams. Longer spans need engineered lumber.

Load distribution pattern. 'uniform' = uniformly distributed load (w in plf). 'point_center' = single concentrated load at midspan. If omitted, defaults to 'uniform'.

Total uniformly distributed load in pounds per linear foot, including dead + live load. Typical residential floor: 50-60 plf per foot of tributary width. Only required when load_type='uniform'.

Concentrated load at midspan in pounds. Only required when load_type='point_center'.

Fraction of total load that is dead load (self-weight + permanent). Used to separate live load for deflection checks. Typical: 0.2-0.5 for floor framing. If omitted, defaults to 0.4.

Service moisture condition per NDS 2.3.3. 'dry' = MC <= 19% (most indoor use). 'wet' = MC > 19% (exterior, ground contact). Applies CM adjustment factors. If omitted, defaults to 'dry'.

Temperature condition per NDS Table 2.3.3. 'normal' = sustained temp <= 100F. 'elevated' = sustained temp > 100F in wet conditions. Applies Ct factors. If omitted, defaults to 'normal'.

NDS load duration factor CD. Common values: 0.9 (dead load), 1.0 (occupancy live), 1.15 (snow), 1.25 (construction), 1.6 (wind/earthquake), 2.0 (impact). If omitted, defaults to 1.0 (occupancy live load).

Set True when 3 or more members are spaced <= 24 in. o.c. and share load via sheathing (e.g., floor joists, rafters). Applies Cr=1.15 for dimension lumber per NDS 4.3.9. If omitted, defaults to False (Cr=1.0).