Simple-Span Floor Beam per NDS 2024

Summary: Design a single-span sawn lumber beam with uniform dead and live load per NDS 2024 §3.3 (flexure), §3.4 (shear), and adjustment factors. This free wood…

Overview

Design a single-span sawn lumber beam with uniform dead and live load per NDS 2024 §3.3 (flexure), §3.4 (shear), and adjustment factors. This free wood beam design calculator NDS applies beam deflection calculator formula and flexure checks. Common for headers, girders, and beams within IBC span table limits.

Problem statement

A sawn lumber floor beam supports floor joists in a residential application. Given: beam size 2×10; species Douglas Fir-Larch (DF-L); grade No. 2; span 12 ft simple (pinned at both ends); uniform dead load 20 plf; uniform live load 80 plf. Load combination D+L governs (CD = 1.0 per NDS Table 2.3.2). Check flexural and shear capacity per NDS 2024 §3.3 and §3.4. Verify deflection L/360 for live load (IBC Table 1604.3). Sawn lumber is the most common product for headers, girders, and beams within residential construction.

Workflow in StructSuite

StructSuite's free structural design software provides NDS design: open the Wood Beam module. In Step 1 Geometry: enter span 12 ft; set both supports to Pinned; leave roof slope at 0 for a horizontal beam. In Loads: add two uniform load items—Type D, 20 plf; Type L, 80 plf. In Materials: select Sawn Lumber, Species Douglas Fir-Larch, Grade No. 2, Size 2×10. In Design Parameters: deflection limit L/360. StructSuite runs beam analysis, applies NDS 2024 Eq 3.3-1 (flexure), Eq 3.4-2 (shear), size factor CF from Table 4A. Simple span maximum moment M = wL²/8 at midspan.

Design considerations (excerpt)

Beams/headers carry joist loads. Moment M = wL²/8 for simple span—span length dominates. 12 ft is common for residential headers; 14–16 ft may need LVL. Single beam (not repetitive) gets no Cr factor. Span length affects moment (∝ L²) and deflection (∝ L⁴). 12 ft vs 14 ft: 36% more moment, 95% more deflection. Pinned ends = simple support; fixed ends reduce moment but rarely used for wood. Slope length for rafters > horizontal projection. NDS flexure and shear; deflection often governs long spans. CD: D+L=1.0, snow/roof live=1.15, wind/seismic=1.6. Short-duration loads (W, E) get higher allowable stress. Governing combo has highest D/C ratio.

100 plf total (20 D + 80 L) on 12 ft: M =…

Related terms

• StructSuite
• structural engineering
• design example
• wood beam
• NDS 2024
• IBC
• nds simple span beam

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