Wood Beam (LRFD, NDS 2018)

Design and verify wood beams to NDS 2018 LRFD, bending (φMn ≥ Mu), shear (φVn ≥ Vu), bearing, and three deflection limits, each shown with the governing NDS adjustment factors and code reference. Load reactions at each support link directly to connected column and footing calculations so changes propagate automatically through the full load path. Supports simple and continuous spans, multi-ply beams, and flitch plate composite configurations.

This calculator uses an earlier code edition (NDS 2018 (LRFD)). It stays available for existing projects. For new designs, check the [Calculator Library](/docs/calculators/us) for the current edition. ## Worked example See [Worked Example: Wood Beam to NDS 2018](/docs/running-calculations/example-calculations/us/worked-example-us-wood-beam) for a full worked example with this calculator. ## Method & scope | Property | Detail | | ---------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Design standards | NDS 2018 (LRFD) | | Regions | United States | | Presets | Generic Beam, Generic Flitch Beam, Floor Joist, Floor Girder, Ceiling Joist, Hip / Valley, Rafter, Ridge Beam, and 5 more | | What it checks | Design method: LRFD per NDS 2018, Reference design values and adjustment factors, Bending check, Shear check, Bearing (compression perpendicular to grain), Deflection checks, Flitch plate and multi-ply beams | #### Calculation method ##### Design method: LRFD per NDS 2018 The calculator applies Load and Resistance Factor Design as specified in NDS 2018. Every load combination entered (dead, live, roof live, snow, wind, seismic) is factored using ASCE 7 load factors. The factored demand at each critical section, maximum moment Mu, maximum shear Vu, and bearing stress at each support, is compared against the corresponding factored resistance: φMn, φVn, and φc⊥Fc⊥' respectively. The resistance factors are fixed per NDS: φb = 0.85 for bending, φv = 0.75 for shear, and φc = 0.90 for compression parallel to grain. This approach makes wind and seismic load combinations directly compatible without the ASD conversion step. ##### Reference design values and adjustment factors For every sawn lumber, glulam, LVL, or I-joist selection, the calculator retrieves the tabulated reference design values (Fb, Fv, Fc⊥, E, Emin) from the NDS 2018 Supplement. It then applies all required adjustment factors per NDS 2018 Section 2: * **CD** (load duration), derived from the governing LRFD load combination * **CM** (wet service), applied when moisture content exceeds 19% for sawn lumber * **Ct** (temperature), for elevated temperature environments * **CF or Cv** (size or volume), size factor for sawn lumber, volume factor for glulam * **Cr** (repetitive member), for closely spaced members sharing load * **CL** (beam stability), calculated from the slenderness ratio RB based on the lateral bracing configuration entered The adjusted design value F'b (LRFD) = Fb × KF × φb × λ × (all applicable C factors), where KF is the format conversion factor and λ is the time effect factor per NDS 2018 Appendix N. ##### Bending check The critical moment Mu is computed by structural analysis across all spans and load combinations simultaneously. The factored bending resistance is φMn = φb × F'b × S, where S is the section modulus of the selected member. For multi-span continuous beams with unlimited supports, the calculator determines the governing span and load combination automatically. The utilization ratio Mu / φMn must be ≤ 1.0 to pass. ##### Shear check Shear Vu is taken conservatively at the face of each support. The factored shear resistance is φVn = φv × F'v × (2/3 × A) for rectangular sections. For I-joists, the calculator uses the manufacturer-specified allowable shear capacities. Utilization Vu / φVn must be ≤ 1.0. ##### Bearing (compression perpendicular to grain) At each support, the bearing stress is checked against the factored bearing resistance φc⊥ × Fc⊥', where the bearing length is entered per support. The bearing area factor Cb may increase the allowable bearing stress for short bearing lengths per NDS 2018 Section 3.10. Utilization must be ≤ 1.0 at every support. ##### Deflection checks Three independent deflection limits are checked for each span: * **Short-term (live load only):** Typically L/360 for floors, L/240 for roofs, configurable per span * **Long-term (total load with creep):** Typically L/240, with long-term creep factor applied per NDS 2018 Section 3.5 * **Hard absolute limit:** A fixed maximum deflection (default 2 in / 50 mm) regardless of span length Creep for sawn lumber and glulam uses the NDS duration of load and moisture adjustment. When shear deflections are significant for deep short-span members, the calculator adds a shear deflection component per an NDS-referenced approximation method. ##### Flitch plate and multi-ply beams For flitch plate configurations, the calculator computes the composite transformed section properties based on the steel-to-wood modular ratio. Bending capacity accounts for the composite section, but shear and bearing are assigned entirely to the wood elements as a conservative simplification. The CL stability factor is calculated using the wood section only. Multi-ply sawn lumber beams in strong-axis bending are checked as a single composite section assuming full load sharing between plies. ## How to use it Open it from **Run calc** in the About this calculator panel above. To start from a typical setup, choose one of the presets listed there. Work through the input sections from top to bottom. Click any input label to see its reference explanation, clause, conditions and assumptions. See [Checks, References, Conditions and Assumptions](/docs/running-calculations/checking-results/checks-references-conditions-assumptions). Check the utilization of each governing check in the summary, then export a PDF report. See [Views and Export](/docs/running-calculations/exporting-reports/views-and-export). ## Common questions Load and Resistance Factor Design (LRFD) per NDS 2018. Factored demands (Mu, Vu) are compared against factored resistances (φMn, φVn) using the NDS resistance factors for wood (φb = 0.85 for bending, φv = 0.75 for shear). Load combinations follow ASCE 7. All applicable adjustment factors, wet service, temperature, size, repetitive member, and lateral stability (CL), are applied per NDS 2018 Section 2. Span configuration (simple, continuous, cantilever, inclined), wood species and grade, section size or selection from the built-in library of thousands of US sections (sawn lumber, glulam, LVL, I-joists), LRFD load combinations (dead, live, roof live, wind, snow, seismic), support conditions, and lateral bracing arrangement. Reference design values are pulled automatically from the NDS Supplement for the selected species and grade. The calculator checks factored bending (φMn ≥ Mu), factored shear (φVn ≥ Vu), and bearing (compression perpendicular to grain) at each support. Deflection is checked against three configurable limits: short-term live load, long-term total load including creep, and a hard absolute limit. Results are displayed as utilization ratios with pass/fail status and the governing NDS adjustment factors shown for each check. Yes. The calculator supports flitch plate beams (steel plate sandwiched between wood members) with composite section properties checked for combined capacity. Multi-ply sawn lumber beams are supported for strong-axis bending. For flitch beams, shear and bearing are conservatively assigned 100% to the wood, and the flitch plates do not affect the CL stability factor calculation. Use LRFD when your load combinations are governed by wind or seismic loads specified under ASCE 7 factored combinations, the φ-factors and load factors align naturally with those demands and remove the need to convert to equivalent ASD loads. ASD is more common for routine residential and light commercial gravity framing. Both methods are available on Calcs.com for NDS 2018 and NDS 2024. Yes, load linking is one of the core workflow benefits. Support reactions from the beam (dead, live, wind, snow, seismic by load case) flow directly into any connected column calculation in the same project. Those column reactions then link automatically to the footing calculation below. When you change a beam span, section, or load, every downstream calculation, column capacity, footing bearing pressure, and reinforcement, updates without re-entering a single value. ## Next steps Complete list of Calcs.com design calculators available for United States projects (AISC, ACI, NDS, ASCE 7, IBC, and related standards). NDS 2024 LRFD wood beam: bending, shear, bearing, three deflection checks with conversion and time effect factors. Multi-ply, flitch plate, inclined. Design wood columns and studs to NDS 2018 (LRFD). An earlier code edition, kept for existing projects. Design wood beams to NDS 2018 (ASD): bending, shear, bearing and deflection. An earlier code edition, kept for existing projects. Design wood columns and studs to NDS 2018 (ASD). An earlier code edition, kept for existing projects. Design rafters, hip beams and other inclined members: set the slope, choose plan or inclined view, pick a load orientation, or convert lengths with formulas. Design wood beams to NDS 2024 (ASD): bending, shear, bearing and three deflection limits, with multi-ply and flitch plate options. Design simple and complex span wood joists, rafters and ridge beams to NDS with the Calcs.com Wood Beam calculator, ASD or LRFD.