Cantilever Beam per NDS 2024

Summary: Design a sawn lumber cantilever (fixed at one end, free at the other). Common for deck overhangs, balcony ledgers, and roof overhangs. A 2×8 Douglas…

Overview

Design a sawn lumber cantilever (fixed at one end, free at the other). Common for deck overhangs, balcony ledgers, and roof overhangs.

Problem statement

A 2×8 Douglas Fir-Larch No. 2 cantilever extends 4 ft beyond the support (fixed at building, free at end). Uniform dead 8 plf, live 30 plf. CD = 1.0. Check capacity. Cantilever has maximum moment at fixed end; deflection often governs at free end.

Workflow in StructSuite

StructSuite's free wood beam calculator NDS: open the Wood Beam module. Enter span [4]. Set left support = Fixed, right support = Free (cantilever). Add uniform load D 8 plf, L 30 plf. StructSuite analyzes cantilever—Mmax at fixed end, Δmax at free end. Fixed-free is one of six support types in NDS Table G1 (though Table G1 is for columns; beam analysis uses support boundary conditions).

Design considerations (excerpt)

Cantilever: M_max at fixed end = wL²/2 (vs wL²/8 for simple span). Same load, 4× moment—cantilevers are moment-critical. Common for deck overhangs (1–4 ft), balcony ledgers, roof overhangs. No IBC tables—NDS required. 4 ft cantilever: short, so shear rarely governs. Moment at fixed end = 38×4²/2 = 304 ft-lb for 38 plf. Doubling length quadruples moment. Connection at fixed end must transfer moment—often through ledger or joist hangers. Fixed-free boundary: reaction at support = wL; moment = wL²/2. Tip deflection Δ = wL⁴/(8EI)—deflection often governs for short cantilevers. L/240 for deck; L/360 if supporting rigid finish.

38 plf (8 D + 30 L) typical deck: decking 2.5 psf, joist 1.5 plf,…

Related terms

• StructSuite
• structural engineering
• design example
• wood beam
• NDS 2024
• nds cantilever

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