Wood Beam / Joist Design
Determine the required sawn lumber size for a simply supported beam or joist. Computes the adjusted bending stress (Fb'), adjusted shear stress (Fv'), and checks actual stresses against allowable values per NDS 2024. Verifies deflection limits under total load (L/240) and live load only (L/360). Includes all applicable NDS adjustment factors: CD, CM, Ct, CL, CF, Cfu, Ci, Cr.
What this calculates
Adjusted allowable bending stress Fb' = Fb · CD · CM · Ct · CL · CF · Cfu · Ci · Cr, adjusted allowable shear stress Fv' = Fv · CD · CM · Ct · Ci, actual bending stress fb = M/Sx, actual shear stress fv = 3V/(2bd), and midspan deflection Δ = 5wL⁴/(384EI). Reports demand-to-capacity ratios for bending, shear, and deflection.
Inputs
Clear span between supports
Distributed dead load per linear foot
Distributed live load per linear foot
Nominal width of lumber (e.g. 2 for 2× member)
Nominal depth of lumber (e.g. 10 for 2×10)
Tabulated reference bending design value
Tabulated reference shear design value
Tabulated reference modulus of elasticity
Load duration factor (e.g. 1.0 for normal, 1.15 for snow, 1.25 for construction)
Outputs
Allowable bending stress with all adjustment factors
Computed bending stress M/S
Bending demand-to-capacity ratio — must be ≤ 1.0
Allowable shear stress with adjustment factors
Computed shear stress 3V/(2A)
Midspan deflection under total load
Midspan deflection under live load only
Methodology
Per NDS 2024 Sections 3.3 (bending), 3.4 (shear), and 3.5 (deflection). Reference design values from NDS Supplement Table 4A (Visually Graded Dimension Lumber). Adjustment factors per NDS Table 4.3.1: CD (load duration), CM (wet service), Ct (temperature), CL (beam stability, per Section 3.3.3), CF (size factor), Cfu (flat use), Ci (incising), Cr (repetitive member). Shear check uses fv = 3V/(2A) per Section 3.4.2. Deflection per Section 3.5 with E' = E · CM · Ct · Ci.
Code References
This template is coming soon
We’re building it. In the meantime, you can create this calculation yourself in EngCanvas — unit-aware math, your own formulas, and one-click PDF export.
Related templates
Timber Bolted Connection
Compute the reference and adjusted lateral design value (Z) for bolted connections in wood per NDS 2024 Chapter 12.
W-Shape Beam Flexure Check
Check the flexural capacity of a wide-flange steel beam for yielding and lateral-torsional buckling per AISC 360-22 Chapter F.