Architecture

Wood Beam Span Table

Maximum simple-span tables for the beams you actually use — 2x lumber, multi-ply built-ups, and LVL. Three load cases (residential floor, roof, heavy floor) across SPF, Doug Fir, Southern Pine, and LVL. Use this to sanity-check a quote, scope a remodel, or pick a beam before you go to the engineer.

⚠ Preliminary sizing only

These tables apply published Fb and E values to a uniformly-loaded simple span. They don't include lateral bracing checks, bearing checks at the supports, concentrated point loads, or load-duration factor adjustments. A residential floor beam with no funny conditions is the safe use case. Anything weirder needs an engineer.

Load case: Species:

Beam	4 ft trib	6 ft trib	8 ft trib	10 ft trib	12 ft trib	14 ft trib	16 ft trib
2×6 (single)	4.0	3.5	3.0	2.5	2.5	2.0	2.0
2×8 (single)	5.5	4.5	4.0	3.5	3.0	3.0	2.5
2×10 (single)	7.0	6.0	5.0	4.5	4.0	3.5	3.5
2×12 (single)	9.0	7.0	6.0	5.5	5.0	4.5	4.5
(2) 2×8 ply	8.0	6.5	5.5	5.0	4.5	4.0	4.0
(2) 2×10 ply	10.0	8.5	7.0	6.5	6.0	5.5	5.0
(2) 2×12 ply	12.5	10.0	9.0	8.0	7.0	6.5	6.0
(3) 2×10 ply	12.5	10.0	9.0	8.0	7.0	6.5	6.0
(3) 2×12 ply	15.5	12.5	11.0	9.5	9.0	8.0	7.5

Beam	4 ft trib	6 ft trib	8 ft trib	10 ft trib	12 ft trib	14 ft trib	16 ft trib
2×6 (single)	4.5	3.5	3.0	3.0	2.5	2.5	2.0
2×8 (single)	6.0	5.0	4.0	3.5	3.5	3.0	3.0
2×10 (single)	8.0	6.5	5.5	5.0	4.5	4.0	4.0
2×12 (single)	9.5	7.5	6.5	6.0	5.5	5.0	4.5
(2) 2×8 ply	8.5	7.0	6.0	5.5	5.0	4.5	4.0
(2) 2×10 ply	11.0	9.0	8.0	7.0	6.5	6.0	5.5
(2) 2×12 ply	13.5	11.0	9.5	8.5	7.5	7.0	6.5
(3) 2×10 ply	13.5	11.0	9.5	8.5	8.0	7.0	6.5
(3) 2×12 ply	16.5	13.5	11.5	10.5	9.5	9.0	8.0

Beam	4 ft trib	6 ft trib	8 ft trib	10 ft trib	12 ft trib	14 ft trib	16 ft trib
2×6 (single)	5.0	4.0	3.5	3.0	3.0	2.5	2.5
2×8 (single)	6.5	5.5	4.5	4.0	3.5	3.5	3.0
2×10 (single)	8.5	7.0	6.0	5.5	5.0	4.5	4.0
2×12 (single)	10.5	8.5	7.5	6.5	6.0	5.5	5.0
(2) 2×8 ply	9.5	7.5	6.5	6.0	5.5	5.0	4.5
(2) 2×10 ply	12.0	10.0	8.5	7.5	7.0	6.5	6.0
(2) 2×12 ply	15.0	12.0	10.5	9.5	8.5	8.0	7.5
(3) 2×10 ply	15.0	12.0	10.5	9.5	8.5	8.0	7.5
(3) 2×12 ply	18.0	15.0	13.0	11.5	10.5	9.5	9.0

Beam	4 ft trib	6 ft trib	8 ft trib	10 ft trib	12 ft trib	14 ft trib	16 ft trib
1¾″ × 9¼″ LVL	11.5	10.0	9.0	8.5	8.0	7.0	7.0
1¾″ × 11⅞″ LVL	14.5	12.5	11.5	10.5	10.0	9.5	9.0
1¾″ × 14″ LVL	17.5	15.0	13.5	12.5	12.0	11.0	10.5
1¾″ × 16″ LVL	20.0	17.5	15.5	14.5	13.5	12.5	12.0
(2) 1¾″ × 11⅞″ LVL	18.5	16.0	14.5	13.5	12.5	12.0	11.5
(2) 1¾″ × 14″ LVL	22.0	19.0	17.5	16.0	15.0	14.5	13.5

Beam	4 ft trib	6 ft trib	8 ft trib	10 ft trib	12 ft trib	14 ft trib	16 ft trib
2×6 (single)	5.5	4.5	3.5	3.0	3.0	2.5	2.5
2×8 (single)	7.0	5.5	5.0	4.5	4.0	3.5	3.5
2×10 (single)	9.0	7.5	6.5	5.5	5.0	4.5	4.5
2×12 (single)	11.0	9.0	8.0	7.0	6.5	6.0	5.5
(2) 2×8 ply	10.0	8.0	7.0	6.5	5.5	5.5	5.0
(2) 2×10 ply	13.0	10.5	9.0	8.0	7.5	7.0	6.5
(2) 2×12 ply	16.0	13.0	11.0	10.0	9.0	8.5	8.0
(3) 2×10 ply	16.0	13.0	11.0	10.0	9.0	8.5	8.0
(3) 2×12 ply	19.5	16.0	13.5	12.0	11.0	10.0	9.5

Beam	4 ft trib	6 ft trib	8 ft trib	10 ft trib	12 ft trib	14 ft trib	16 ft trib
2×6 (single)	6.0	4.5	4.0	3.5	3.0	3.0	3.0
2×8 (single)	7.5	6.0	5.5	5.0	4.5	4.0	3.5
2×10 (single)	10.0	8.0	7.0	6.0	5.5	5.0	5.0
2×12 (single)	12.0	10.0	8.5	7.5	7.0	6.5	6.0
(2) 2×8 ply	11.0	9.0	7.5	7.0	6.0	5.5	5.5
(2) 2×10 ply	14.0	11.5	10.0	9.0	8.0	7.5	7.0
(2) 2×12 ply	17.0	14.0	12.0	10.5	10.0	9.0	8.5
(3) 2×10 ply	17.0	14.0	12.0	11.0	10.0	9.0	8.5
(3) 2×12 ply	21.0	17.0	15.0	13.0	12.0	11.0	10.5

Beam	4 ft trib	6 ft trib	8 ft trib	10 ft trib	12 ft trib	14 ft trib	16 ft trib
2×6 (single)	6.5	5.0	4.5	4.0	3.5	3.5	3.0
2×8 (single)	8.5	7.0	6.0	5.0	5.0	4.5	4.0
2×10 (single)	11.0	9.0	7.5	6.5	6.0	5.5	5.5
2×12 (single)	13.0	10.5	9.5	8.5	7.5	7.0	6.5
(2) 2×8 ply	12.0	10.0	8.5	7.5	7.0	6.5	6.0
(2) 2×10 ply	15.5	12.5	11.0	9.5	9.0	8.0	7.5
(2) 2×12 ply	19.0	15.5	13.0	12.0	10.5	10.0	9.5
(3) 2×10 ply	19.0	15.5	13.5	12.0	11.0	10.0	9.5
(3) 2×12 ply	23.0	19.0	16.0	14.5	13.0	12.0	11.5

Beam	4 ft trib	6 ft trib	8 ft trib	10 ft trib	12 ft trib	14 ft trib	16 ft trib
1¾″ × 9¼″ LVL	15.0	13.0	12.0	11.0	10.0	9.0	8.5
1¾″ × 11⅞″ LVL	19.5	17.0	15.5	14.0	13.0	12.0	11.0
1¾″ × 14″ LVL	23.0	20.0	18.5	16.5	15.0	14.0	13.0
1¾″ × 16″ LVL	26.5	23.0	21.0	19.0	17.5	16.0	15.0
(2) 1¾″ × 11⅞″ LVL	24.5	21.5	19.5	18.0	17.0	16.0	15.5
(2) 1¾″ × 14″ LVL	29.0	25.5	23.0	21.5	20.0	19.0	18.5

Beam	4 ft trib	6 ft trib	8 ft trib	10 ft trib	12 ft trib	14 ft trib	16 ft trib
2×6 (single)	3.0	2.5	2.0	2.0	1.5	1.5	1.5
2×8 (single)	4.0	3.5	3.0	2.5	2.0	2.0	2.0
2×10 (single)	5.5	4.0	3.5	3.0	3.0	2.5	2.5
2×12 (single)	6.5	5.0	4.5	4.0	3.5	3.5	3.0
(2) 2×8 ply	6.0	4.5	4.0	3.5	3.5	3.0	3.0
(2) 2×10 ply	7.5	6.0	5.5	4.5	4.0	4.0	3.5
(2) 2×12 ply	9.0	7.5	6.5	5.5	5.0	5.0	4.5
(3) 2×10 ply	9.5	7.5	6.5	6.0	5.5	5.0	4.5
(3) 2×12 ply	11.5	9.0	8.0	7.0	6.5	6.0	5.5

Beam	4 ft trib	6 ft trib	8 ft trib	10 ft trib	12 ft trib	14 ft trib	16 ft trib
2×6 (single)	3.5	2.5	2.5	2.0	2.0	1.5	1.5
2×8 (single)	4.5	3.5	3.0	2.5	2.5	2.5	2.0
2×10 (single)	5.5	4.5	4.0	3.5	3.0	3.0	2.5
2×12 (single)	7.0	5.5	5.0	4.5	4.0	3.5	3.5
(2) 2×8 ply	6.5	5.0	4.5	4.0	3.5	3.5	3.0
(2) 2×10 ply	8.0	6.5	5.5	5.0	4.5	4.5	4.0
(2) 2×12 ply	10.0	8.0	7.0	6.0	5.5	5.0	5.0
(3) 2×10 ply	10.0	8.0	7.0	6.5	5.5	5.5	5.0
(3) 2×12 ply	12.5	10.0	8.5	7.5	7.0	6.5	6.0

Beam	4 ft trib	6 ft trib	8 ft trib	10 ft trib	12 ft trib	14 ft trib	16 ft trib
2×6 (single)	3.5	3.0	2.5	2.0	2.0	2.0	1.5
2×8 (single)	5.0	4.0	3.5	3.0	2.5	2.5	2.5
2×10 (single)	6.5	5.0	4.5	4.0	3.5	3.0	3.0
2×12 (single)	7.5	6.0	5.5	5.0	4.5	4.0	3.5
(2) 2×8 ply	7.0	5.5	5.0	4.5	4.0	3.5	3.5
(2) 2×10 ply	9.0	7.5	6.5	5.5	5.0	4.5	4.5
(2) 2×12 ply	11.0	9.0	7.5	7.0	6.0	6.0	5.5
(3) 2×10 ply	11.0	9.0	8.0	7.0	6.5	6.0	5.5
(3) 2×12 ply	13.5	11.0	9.5	8.5	7.5	7.0	6.5

Beam	4 ft trib	6 ft trib	8 ft trib	10 ft trib	12 ft trib	14 ft trib	16 ft trib
1¾″ × 9¼″ LVL	9.0	8.0	7.0	6.5	6.0	5.5	5.0
1¾″ × 11⅞″ LVL	12.0	10.5	9.0	8.0	7.5	7.0	6.5
1¾″ × 14″ LVL	14.0	12.5	11.0	9.5	9.0	8.0	7.5
1¾″ × 16″ LVL	16.0	14.0	12.5	11.0	10.0	9.5	8.5
(2) 1¾″ × 11⅞″ LVL	15.0	13.0	12.0	11.0	10.5	10.0	9.0
(2) 1¾″ × 14″ LVL	18.0	15.5	14.0	13.0	12.5	11.5	11.0

Read across to find a tributary width that matches your framing — that's the span you can carry. Spans are rounded down for safety; the underlying math is exact.

How to read this table

Pick the load case that matches your situation, pick the species/grade you'll be buying, then read down to the beam you're considering and across to your tributary width. The number is the maximum simple span (in feet) before either bending or deflection runs out.

Quick example: living room remodel

You're removing a bearing wall in a single-story house. Joists span 12 feet to the wall on each side, so tributary width on your new beam is 12/2 + 12/2 = 12 ft. Residential floor load (55 psf, L/360), Doug Fir lumber. A (2) 2×10 carries about 9 ft at 12 ft trib; a (2) 2×12 about 11 ft; a 1¾″ × 11⅞″ LVL about 13 ft. If your opening is 14 ft, you need a (2) 1¾″ × 11⅞″ LVL or a 14″ LVL.

The math behind the numbers

For a uniformly-loaded simple span:

Bending check. Maximum bending moment M = wL²/8. Allowable moment is F_b × S, where S is the section modulus. Solve for L: L = sqrt(8 · F_b · S / w).
Deflection check. Maximum deflection Δ = 5wL⁴ / (384 EI). Setting Δ ≤ L/defl-limit and solving for L: L = cbrt(384 · E · I / (5 · w · defl)).
w is the linear load in lb/in (psf × tributary feet ÷ 12).
The shorter of the two spans is the answer. For shallow beams at high loads, bending governs. For long, deep beams at lower loads, deflection governs.

L/360 vs L/240 — which to use

L/360. Standard for residential floors. A 12-ft span deflects no more than 12 × 12 / 360 = 0.4 inches under full design load. Felt as "solid" underfoot.
L/240. Roofs and floors without finishes that crack. Slightly bouncy but not alarming.
L/480. Tile / stone floors that crack with movement. Cuts span ~10% from L/360.

What this table does NOT account for

Point loads. A post landing mid-beam (from a second-story wall, a king-post truss, a girder) changes the math completely. Use beam-software or an engineer.
Cantilevers. Different moment and deflection equations.
Load duration factor (C_D). NDS allows a 15% bump for snow loads (short-duration) and a 60% bump for wind/seismic. This table uses C_D = 1.0 (normal duration) — conservative for roof beams.
Lateral-torsional buckling. Tall, narrow beams without bracing can fail sideways before reaching the bending limit. Always sheathe the top of a floor beam.
Bearing at supports. A 1¾″ LVL bearing on a 2x sill needs at least 1.5 inches of bearing length — confirm separately.
Notches and holes. Plumbers love to drill through beams. Notches in the tension face reduce capacity dramatically.

FAQ

How are these spans different from my framing code book? +

Some code-book tables include the load duration factor for snow (which bumps roof allowables ~15%), some don't. Some round to whole feet, some to inches. The math here is the textbook simple-span case rounded down to half-foot increments — conservative on purpose.

Why doesn't the table show shear? +

For typical residential beams (clear of large holes / notches), shear rarely governs before bending and deflection at these span lengths. The Timber Frame Span calc shows shear explicitly because heavy timbers with cut joinery often do hit shear first.

SPF vs DF — does it actually matter? +

Yes. Doug Fir is about 18% stronger in bending and ~14% stiffer than SPF. On a borderline span you might step up one beam size when you switch from DF to SPF, or pick up a foot of span going the other direction. Buy what your lumberyard stocks.

Multi-ply built-up beams — is the strength really additive? +

Approximately, yes — as long as the plies are properly nailed or bolted together. Most codes require nailing schedules like 10d nails at 12″ o.c. each face, staggered. Use construction adhesive between plies for extra stiffness. Glulam or LVL is structurally cleaner.

I have a point load in the middle — what do I do? +

Add the point load reaction × 2 to your linear load as a rough estimate (this overestimates moment a bit) and look up the resulting span. For anything serious, run it through real beam software or hand it to an engineer.

Can I use this for headers over door / window openings? +

Yes, if the header carries only floor or roof load above it (no point loads from posts, trusses, or shear walls). Read tributary width as half the floor/roof above on each side of the wall.

Why are my LVL spans not much better than (3) 2×12? +

Because (3) 2×12 has more cross-section than a 14″ LVL. Where LVL really wins is on long spans where deflection controls — its E (2.0M) is 25% higher than DF, and that scales as the cube root in deflection-limited spans. For short, heavily-loaded spans, multi-ply 2x is often the cheaper answer.