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BuyIRC Deck Beam Span Tables
Species × ply × size × effective joist span grids from IRC 2021 Table R507.5(1) — bookmarkable reference, still a starting point
These grids are the same cells the deck beam span calculator and the deck post spacing calculator return. Values are IRC 2021 Table R507.5(1) for 40 psf live load, 10 psf dead load, L/360, No. 2, wet service. Columns are effective deck joist span length in feet. They are not local law by themselves.
How to use a cell: guide. Beam vs joist: comparison. Existing sag: troubleshooting. Joists: IRC joist span tables.
Look up one combination.Species, plies, size, effective joist span.
Open Calculator →Southern Pine #2
IRC 2021 Table R507.5(1) — Deck beams — 40 psf live load. 40 psf live load (snow not concurrent); 10 psf dead load; L/360 at main span; No. 2, wet service factor included. Columns are effective deck joist span (feet).
| Plies × size | 6 ft | 8 ft | 10 ft | 12 ft | 14 ft | 16 ft | 18 ft |
|---|---|---|---|---|---|---|---|
| 1-ply 2x6 | 4′-7″ | 4′-0″ | 3′-7″ | 3′-3″ | 3′-0″ | 2′-10″ | 2′-8″ |
| 1-ply 2x8 | 5′-11″ | 5′-1″ | 4′-7″ | 4′-2″ | 3′-10″ | 3′-7″ | 3′-5″ |
| 1-ply 2x10 | 7′-0″ | 6′-0″ | 5′-5″ | 4′-11″ | 4′-7″ | 4′-3″ | 4′-0″ |
| 1-ply 2x12 | 8′-3″ | 7′-1″ | 6′-4″ | 5′-10″ | 5′-5″ | 5′-0″ | 4′-9″ |
| 2-ply 2x6 | 6′-11″ | 5′-11″ | 5′-4″ | 4′-10″ | 4′-6″ | 4′-3″ | 4′-0″ |
| 2-ply 2x8 | 8′-9″ | 7′-7″ | 6′-9″ | 6′-2″ | 5′-9″ | 5′-4″ | 5′-0″ |
| 2-ply 2x10 | 10′-4″ | 9′-0″ | 8′-0″ | 7′-4″ | 6′-9″ | 6′-4″ | 6′-0″ |
| 2-ply 2x12 | 12′-2″ | 10′-7″ | 9′-5″ | 8′-7″ | 8′-0″ | 7′-5″ | 7′-0″ |
| 3-ply 2x6 | 8′-6″ | 7′-5″ | 6′-8″ | 6′-1″ | 5′-8″ | 5′-3″ | 4′-11″ |
| 3-ply 2x8 | 10′-11″ | 9′-6″ | 8′-6″ | 7′-9″ | 7′-2″ | 6′-8″ | 6′-4″ |
| 3-ply 2x10 | 13′-0″ | 11′-2″ | 10′-0″ | 9′-2″ | 8′-6″ | 7′-11″ | 7′-6″ |
| 3-ply 2x12 | 15′-3″ | 13′-3″ | 11′-10″ | 10′-9″ | 10′-0″ | 9′-4″ | 8′-10″ |
Douglas Fir-Larch / Hem-Fir / SPF #2
One IRC row. Incising factor included. Hem-Fir and SPF use these same cells.
| Plies × size | 6 ft | 8 ft | 10 ft | 12 ft | 14 ft | 16 ft | 18 ft |
|---|---|---|---|---|---|---|---|
| 1-ply 2x6 | 4′-1″ | 3′-6″ | 3′-0″ | 2′-8″ | 2′-5″ | 2′-3″ | 2′-1″ |
| 1-ply 2x8 | 5′-6″ | 4′-8″ | 4′-0″ | 3′-6″ | 3′-2″ | 2′-11″ | 2′-9″ |
| 1-ply 2x10 | 6′-8″ | 5′-10″ | 5′-1″ | 4′-6″ | 4′-1″ | 3′-9″ | 3′-6″ |
| 1-ply 2x12 | 7′-9″ | 6′-9″ | 6′-0″ | 5′-6″ | 5′-0″ | 3′-9″ | 3′-6″ |
| 2-ply 2x6 | 6′-1″ | 5′-3″ | 4′-9″ | 4′-4″ | 3′-11″ | 3′-7″ | 3′-3″ |
| 2-ply 2x8 | 8′-2″ | 7′-1″ | 6′-4″ | 5′-9″ | 5′-2″ | 4′-8″ | 4′-4″ |
| 2-ply 2x10 | 10′-0″ | 8′-7″ | 7′-9″ | 7′-0″ | 6′-6″ | 6′-0″ | 5′-6″ |
| 2-ply 2x12 | 11′-7″ | 10′-0″ | 8′-11″ | 8′-2″ | 7′-7″ | 7′-1″ | 6′-8″ |
| 3-ply 2x6 | 7′-8″ | 6′-8″ | 6′-0″ | 5′-6″ | 5′-1″ | 4′-9″ | 4′-6″ |
| 3-ply 2x8 | 10′-3″ | 8′-10″ | 7′-11″ | 7′-3″ | 6′-8″ | 6′-3″ | 5′-11″ |
| 3-ply 2x10 | 12′-6″ | 10′-10″ | 9′-8″ | 8′-10″ | 8′-2″ | 7′-8″ | 7′-2″ |
| 3-ply 2x12 | 14′-6″ | 12′-7″ | 11′-3″ | 10′-3″ | 9′-6″ | 8′-11″ | 8′-5″ |
Redwood / Western Cedars / Ponderosa / Red Pine #2
One IRC row. Incising factor not included.
| Plies × size | 6 ft | 8 ft | 10 ft | 12 ft | 14 ft | 16 ft | 18 ft |
|---|---|---|---|---|---|---|---|
| 1-ply 2x6 | 4′-2″ | 3′-7″ | 3′-1″ | 2′-9″ | 2′-6″ | 2′-3″ | 2′-2″ |
| 1-ply 2x8 | 5′-4″ | 4′-7″ | 4′-1″ | 3′-7″ | 3′-3″ | 3′-0″ | 2′-10″ |
| 1-ply 2x10 | 6′-6″ | 5′-7″ | 5′-0″ | 4′-7″ | 4′-2″ | 3′-10″ | 3′-7″ |
| 1-ply 2x12 | 7′-6″ | 6′-6″ | 5′-10″ | 5′-4″ | 4′-11″ | 4′-7″ | 4′-4″ |
| 2-ply 2x6 | 6′-2″ | 5′-4″ | 4′-10″ | 4′-5″ | 4′-0″ | 3′-8″ | 3′-4″ |
| 2-ply 2x8 | 7′-10″ | 6′-10″ | 6′-1″ | 5′-7″ | 5′-2″ | 4′-10″ | 4′-5″ |
| 2-ply 2x10 | 9′-7″ | 8′-4″ | 7′-5″ | 6′-9″ | 6′-3″ | 5′-10″ | 5′-6″ |
| 2-ply 2x12 | 11′-1″ | 9′-8″ | 8′-7″ | 7′-10″ | 7′-3″ | 6′-10″ | 6′-5″ |
| 3-ply 2x6 | 7′-8″ | 6′-9″ | 6′-0″ | 5′-6″ | 5′-1″ | 4′-9″ | 4′-6″ |
| 3-ply 2x8 | 9′-10″ | 8′-6″ | 7′-7″ | 6′-11″ | 6′-5″ | 6′-0″ | 5′-8″ |
| 3-ply 2x10 | 12′-0″ | 10′-5″ | 9′-4″ | 8′-6″ | 7′-10″ | 7′-4″ | 6′-11″ |
| 3-ply 2x12 | 13′-11″ | 12′-1″ | 10′-9″ | 9′-10″ | 9′-1″ | 8′-6″ | 8′-1″ |
Source and Limits
Values transcribed from IRC 2021 Table R507.5(1) (Maximum Deck Beam Span — 40 PSF Live Load) as published in the Massachusetts Residential Code, 10th edition (IRC 2021 based) on UpCodes. The same cells were cross-checked against Pennsylvania Residential Code 2021 and Utah Residential Code 2021 Table R507.5(1) on UpCodes. No values were interpolated. Southern Pine 2-ply and 3-ply rows also match independently published 2021 IRC R507.5 excerpts.
Not included: Tables R507.5(2) through R507.5(4) (50 / 60 / 70 psf ground snow), Table R507.5(5) factor math inside the grid (convert first, then pick a column), solid 3x/4x timber rows from older editions, Select Structural / #1 / #3, or cantilever of the beam itself (limited to adjacent span / 4). If your job needs those, open the adopted code or hire a licensed engineer.
Citation: 2021 International Residential Code Table R507.5(1); Massachusetts Residential Code, 10th edition (UpCodes, Chapter 5 Floors); Pennsylvania Residential Code 2021 Table R507.5(1); Utah Residential Code 2021 Table R507.5(1).
One combination, not the whole grid?Use the calculator. The yellow starting-point flag is on the result.
Open Calculator →FAQ
Why bookmark this instead of only the calculator?
Because a crew comparing 2-ply vs 3-ply at two joist columns wants the grid. The calculator is for one cell. Both are starting points.
Why do DF-L, Hem-Fir, and SPF match?
Because Table R507.5(1) prints them as one row with the incising factor included. Redwood / cedars / ponderosa / red pine are a different row.
Can I use these numbers as the permit documents?
No. Attach the adopted local tables or engineering. This page is a reference to the 2021 IRC cells listed above.
Any trade
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Framing Layout Gear
Confirm the stamp and the bay. Then layout. The table does not replace a square or a level on an existing sag.
16×24 Framing Square
Mark post layout after the table says the beam reaches. Same square for the deck stairs off that frame.
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Swanson Speed Square
Quick 90s and ply checks. The calculator still wants species from the stamp, not from memory.
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48" Box Beam Level
Existing midspan bounce and sag are a field measurement first. Compare that to the tabulated beam span second.
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7-1/4" Circular Saw
Do not cut a beam longer than the table allows and hope. Add a post, change plies, or get engineering.
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Johnson Stair Gauges
When the deck also needs stairs, lock the square. Beam span and stringer math are separate.
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Look Up the Table Cell
Species, plies, size, effective joist span. Starting point only — verify local code and the stamp.
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