Floor joist span tables (2021 IRC)

Both floor joist tables the 2021 International Residential Code publishes, in full: 2021 IRC Table R502.3.1(1) for residential sleeping areas and 2021 IRC Table R502.3.1(2) for residential living areas. Every size, every species, every grade, every on-center spacing — each table cited where it sits, with a link down to the page for each size.

40 psf live / 10 psf dead / L/360 30 psf live / 10 psf dead / L/360

40 psf live / 10 psf dead / L/360

11’10”

Per 2021 IRC Table R502.3.1(2) — residential living areas, 40 psf live / 10 psf dead / L/360.

A 2×8 Southern pine No. 2 floor joist at 16-inch centers spans up to 11’10” under standard residential living-area loads (2021 IRC Table R502.3.1(2)). Under 2021 IRC Table R502.3.1(1) — residential sleeping areas, 30 psf live / 10 psf dead / L/360 — the same joist is listed at 13’3”.

Which of the two tables applies

The two tables differ in one thing: the live load the floor is checked against. 2021 IRC Table R502.3.1(1) is residential sleeping areas at 30 psf live / 10 psf dead / L/360. 2021 IRC Table R502.3.1(2) is residential living areas at 40 psf live / 10 psf dead / L/360. Both carry the same 10 psf dead load and the same L/360 deflection limit, so the lighter live load is what lets the sleeping-area table list a longer span for the same stick of lumber.

Spacing in these tables is on center. Grade is the grade stamped on the lumber. Species is the species row the table prints, and a joist of one species cannot be read off another species' row — the gap between them is set out on the species page. Point loads, cantilevers beyond the table footnotes, unusual snow loads, or anything else outside the table's stated conditions — that's an engineer's question.

The common case, size by size

No. 2 grade at 16-inch centers under residential living areas, across the 4 species 2021 IRC Table R502.3.1(2) lists. Each size links to its own page, where the full table for that size sits alongside the residential sleeping areas table.

Joist size	Douglas fir-larch	Hem-fir	Southern pine	Spruce-pine-fir
2×6 floor joists	9’9”	9’1”	9’4”	9’4”
2×8 floor joists	12’9”	12’0”	11’10”	12’3”
2×10 floor joists	15’7”	15’2”	14’0”	15’5”
2×12 floor joists	18’1”	17’7”	16’6”	17’10”

2021 IRC Table R502.3.1(2) — residential living areas, 40 psf live / 10 psf dead / L/360, No. 2 grade at 16-inch centers. table source

Residential living areas — the full table

2021 IRC Table R502.3.1(2), every size the table covers. Spacing runs across the top; species and grade run down the side; the blocks are the lumber sizes.

Species and grade	12" on center	16" on center	19.2" on center	24" on center
2×6 floor joists
Douglas fir-larch Select Structural	11’4”	10’4”	9’8”	9’0”
Douglas fir-larch No. 1	10’11”	9’11”	9’4”	8’8”
Douglas fir-larch No. 2	10’9”	9’9”	9’2”	8’3”
Douglas fir-larch No. 3	8’11”	7’8”	7’0”	6’3”
Hem-fir Select Structural	10’9”	9’9”	9’2”	8’6”
Hem-fir No. 1	10’6”	9’6”	9’0”	8’4”
Hem-fir No. 2	10’0”	9’1”	8’7”	7’11”
Hem-fir No. 3	8’8”	7’6”	6’10”	6’2”
Southern pine Select Structural	11’2”	10’2”	9’6”	8’10”
Southern pine No. 1	10’9”	9’9”	9’2”	8’6”
Southern pine No. 2	10’3”	9’4”	8’6”	7’7”
Southern pine No. 3	8’2”	7’1”	6’5”	5’9”
Spruce-pine-fir Select Structural	10’6”	9’6”	9’0”	8’4”
Spruce-pine-fir No. 1	10’3”	9’4”	8’9”	8’1”
Spruce-pine-fir No. 2	10’3”	9’4”	8’9”	8’1”
Spruce-pine-fir No. 3	8’8”	7’6”	6’10”	6’2”
2×8 floor joists
Douglas fir-larch Select Structural	15’0”	13’7”	12’10”	11’11”
Douglas fir-larch No. 1	14’5”	13’1”	12’4”	11’0”
Douglas fir-larch No. 2	14’2”	12’9”	11’8”	10’5”
Douglas fir-larch No. 3	11’3”	9’9”	8’11”	8’0”
Hem-fir Select Structural	14’2”	12’10”	12’1”	11’3”
Hem-fir No. 1	13’10”	12’7”	11’10”	10’10”
Hem-fir No. 2	13’2”	12’0”	11’3”	10’2”
Hem-fir No. 3	11’0”	9’6”	8’8”	7’9”
Southern pine Select Structural	14’8”	13’4”	12’7”	11’8”
Southern pine No. 1	14’2”	12’10”	12’1”	11’3”
Southern pine No. 2	13’6”	11’10”	10’10”	9’8”
Southern pine No. 3	10’3”	8’11”	8’2”	7’3”
Spruce-pine-fir Select Structural	13’10”	12’7”	11’10”	11’0”
Spruce-pine-fir No. 1	13’6”	12’3”	11’6”	10’3”
Spruce-pine-fir No. 2	13’6”	12’3”	11’6”	10’3”
Spruce-pine-fir No. 3	11’0”	9’6”	8’8”	7’9”
2×10 floor joists
Douglas fir-larch Select Structural	19’1”	17’4”	16’4”	15’2”
Douglas fir-larch No. 1	18’5”	16’5”	15’0”	13’5”
Douglas fir-larch No. 2	18’0”	15’7”	14’3”	12’9”
Douglas fir-larch No. 3	13’9”	11’11”	10’11”	9’9”
Hem-fir Select Structural	18’0”	16’5”	15’5”	14’4”
Hem-fir No. 1	17’8”	16’0”	14’10”	13’3”
Hem-fir No. 2	16’10”	15’2”	13’10”	12’5”
Hem-fir No. 3	13’5”	11’8”	10’7”	9’6”
Southern pine Select Structural	18’9”	17’0”	16’0”	14’11”
Southern pine No. 1	18’0”	16’1”	14’8”	13’1”
Southern pine No. 2	16’2”	14’0”	12’10”	11’5”
Southern pine No. 3	12’6”	10’10”	9’10”	8’10”
Spruce-pine-fir Select Structural	17’8”	16’0”	15’1”	14’0”
Spruce-pine-fir No. 1	17’3”	15’5”	14’1”	12’7”
Spruce-pine-fir No. 2	17’3”	15’5”	14’1”	12’7”
Spruce-pine-fir No. 3	13’5”	11’8”	10’7”	9’6”
2×12 floor joists
Douglas fir-larch Select Structural	23’3”	21’1”	19’10”	18’5”
Douglas fir-larch No. 1	22’0”	19’1”	17’5”	15’7”
Douglas fir-larch No. 2	20’11”	18’1”	16’6”	14’9”
Douglas fir-larch No. 3	16’0”	13’10”	12’7”	11’3”
Hem-fir Select Structural	21’11”	19’11”	18’9”	17’5”
Hem-fir No. 1	21’6”	18’10”	17’2”	15’5”
Hem-fir No. 2	20’4”	17’7”	16’1”	14’4”
Hem-fir No. 3	15’7”	13’6”	12’4”	11’0”
Southern pine Select Structural	22’10”	20’9”	19’6”	18’1”
Southern pine No. 1	21’11”	19’1”	17’5”	15’7”
Southern pine No. 2	19’1”	16’6”	15’1”	13’6”
Southern pine No. 3	14’9”	12’10”	11’8”	10’5”
Spruce-pine-fir Select Structural	21’6”	19’6”	18’4”	17’0”
Spruce-pine-fir No. 1	20’7”	17’10”	16’3”	14’7”
Spruce-pine-fir No. 2	20’7”	17’10”	16’3”	14’7”
Spruce-pine-fir No. 3	15’7”	13’6”	12’4”	11’0”

2021 IRC Table R502.3.1(2) — residential living areas, 40 psf live / 10 psf dead / L/360. table source

Residential sleeping areas — the full table

2021 IRC Table R502.3.1(1), on the same 30 psf live / 10 psf dead / L/360 basis, every size the table covers.

Species and grade	12" on center	16" on center	19.2" on center	24" on center
2×6 floor joists
Douglas fir-larch Select Structural	12’6”	11’4”	10’8”	9’11”
Douglas fir-larch No. 1	12’0”	10’11”	10’4”	9’7”
Douglas fir-larch No. 2	11’10”	10’9”	10’1”	9’3”
Douglas fir-larch No. 3	9’11”	8’7”	7’10”	7’0”
Hem-fir Select Structural	11’10”	10’9”	10’1”	9’4”
Hem-fir No. 1	11’7”	10’6”	9’10”	9’2”
Hem-fir No. 2	11’0”	10’0”	9’5”	8’9”
Hem-fir No. 3	9’8”	8’5”	7’8”	6’10”
Southern pine Select Structural	12’3”	11’2”	10’6”	9’9”
Southern pine No. 1	11’10”	10’9”	10’1”	9’4”
Southern pine No. 2	11’3”	10’3”	9’6”	8’6”
Southern pine No. 3	9’2”	7’11”	7’3”	6’5”
Spruce-pine-fir Select Structural	11’7”	10’6”	9’10”	9’2”
Spruce-pine-fir No. 1	11’3”	10’3”	9’8”	8’11”
Spruce-pine-fir No. 2	11’3”	10’3”	9’8”	8’11”
Spruce-pine-fir No. 3	9’8”	8’5”	7’8”	6’10”
2×8 floor joists
Douglas fir-larch Select Structural	16’6”	15’0”	14’1”	13’1”
Douglas fir-larch No. 1	15’10”	14’5”	13’7”	12’4”
Douglas fir-larch No. 2	15’7”	14’2”	13’0”	11’8”
Douglas fir-larch No. 3	12’7”	10’11”	10’0”	8’11”
Hem-fir Select Structural	15’7”	14’2”	13’4”	12’4”
Hem-fir No. 1	15’3”	13’10”	13’0”	12’1”
Hem-fir No. 2	14’6”	13’2”	12’5”	11’4”
Hem-fir No. 3	12’4”	10’8”	9’9”	8’8”
Southern pine Select Structural	16’2”	14’8”	13’10”	12’10”
Southern pine No. 1	15’7”	14’2”	13’4”	12’4”
Southern pine No. 2	14’11”	13’3”	12’1”	10’10”
Southern pine No. 3	11’6”	10’0”	9’1”	8’2”
Spruce-pine-fir Select Structural	15’3”	13’10”	13’0”	12’1”
Spruce-pine-fir No. 1	14’11”	13’6”	12’9”	11’6”
Spruce-pine-fir No. 2	14’11”	13’6”	12’9”	11’6”
Spruce-pine-fir No. 3	12’4”	10’8”	9’9”	8’8”
2×10 floor joists
Douglas fir-larch Select Structural	21’0”	19’1”	18’0”	16’8”
Douglas fir-larch No. 1	20’3”	18’5”	16’9”	15’0”
Douglas fir-larch No. 2	19’10”	17’5”	15’11”	14’3”
Douglas fir-larch No. 3	15’5”	13’4”	12’2”	10’11”
Hem-fir Select Structural	19’10”	18’0”	17’0”	15’9”
Hem-fir No. 1	19’5”	17’8”	16’7”	14’10”
Hem-fir No. 2	18’6”	16’10”	15’6”	13’10”
Hem-fir No. 3	15’0”	13’0”	11’10”	10’7”
Southern pine Select Structural	20’8”	18’9”	17’8”	16’5”
Southern pine No. 1	19’10”	18’0”	16’5”	14’8”
Southern pine No. 2	18’1”	15’8”	14’4”	12’10”
Southern pine No. 3	14’0”	11’1”	11’0”	9’10”
Spruce-pine-fir Select Structural	19’5”	17’8”	16’7”	15’5”
Spruce-pine-fir No. 1	19’0”	17’2”	15’8”	14’1”
Spruce-pine-fir No. 2	19’0”	17’2”	15’8”	14’1”
Spruce-pine-fir No. 3	15’0”	13’0”	11’10”	10’7”
2×12 floor joists
Douglas fir-larch Select Structural	25’7”	23’3”	21’10”	20’3”
Douglas fir-larch No. 1	24’8”	21’4”	19’6”	17’5”
Douglas fir-larch No. 2	23’4”	20’3”	18’6”	16’6”
Douglas fir-larch No. 3	17’10”	15’5”	14’1”	12’7”
Hem-fir Select Structural	24’2”	21’11”	20’8”	19’2”
Hem-fir No. 1	23’7”	21’1”	19’3”	17’2”
Hem-fir No. 2	22’6”	19’8”	17’1”	16’1”
Hem-fir No. 3	17’5”	15’1”	13’9”	12’4”
Southern pine Select Structural	25’1”	22’10”	21’6”	19’11”
Southern pine No. 1	24’2”	21’4”	19’6”	17’5”
Southern pine No. 2	21’4”	18’6”	16’10”	15’1”
Southern pine No. 3	16’6”	14’4”	13’1”	11’8”
Spruce-pine-fir Select Structural	23’7”	21’6”	20’2”	18’9”
Spruce-pine-fir No. 1	23’0”	19’11”	18’3”	16’3”
Spruce-pine-fir No. 2	23’0”	19’11”	18’3”	16’3”
Spruce-pine-fir No. 3	17’5”	15’1”	13’9”	12’4”

2021 IRC Table R502.3.1(1) — residential sleeping areas, 30 psf live / 10 psf dead / L/360. table source

Common questions

Which 2021 IRC floor joist table applies to my room?

2021 IRC Table R502.3.1(1) covers residential sleeping areas at 30 psf live / 10 psf dead / L/360; 2021 IRC Table R502.3.1(2) covers residential living areas at 40 psf live / 10 psf dead / L/360. The same 2×8 Southern pine No. 2 joist at 16-inch centers is listed at 13’3” in the first and 11’10” in the second. Both tables are on this page in full.

How far can a floor joist span?

It depends on the size, species, grade, and spacing — those are the four things the table is read by. For Southern pine No. 2 at 16-inch centers under residential living areas (2021 IRC Table R502.3.1(2)), the table lists 2×6 9’4”, 2×8 11’10”, 2×10 14’0”, 2×12 16’6”. Change any one of the four and you are reading a different cell.

How far apart are floor joists?

At one of the 4 on-center spacings the floor joist tables list — 12, 16, 19.2 or 24 inches, measured center to center. The code does not pick one for you: the spacing is chosen together with the size, species and grade, and it moves the span. For a 2×12 Southern pine No. 2 joist in a living area, 2021 IRC Table R502.3.1(2) lists 19’1” at 12-inch centers, 16’6” at 16-inch centers, 15’1” at 19.2-inch centers, 13’6” at 24-inch centers — the closer the joists, the farther each may span. Neither table lists a spacing wider than 24 inches.

Do these tables cover every species and grade?

These two tables cover 4 species — Douglas fir-larch, Hem-fir, Southern pine, Spruce-pine-fir — in 4 grades: Select Structural, No. 1, No. 2, and No. 3. Lumber outside that set, engineered joists such as I-joists or LVL, and any species-grade combination the table does not list are not on this site. Point loads, cantilevers beyond the table footnotes, unusual snow loads, or anything else outside the table's stated conditions — that's an engineer's question.

The rest of the framing

Floor joist sizes: 2×6 floor joists · 2×8 floor joists · 2×10 floor joists · 2×12 floor joists

Other assemblies: ceiling joist span tables · rafter span tables · deck joist span tables · deck beam spans · header and girder spans

Local codes amend these tables and your inspector has the final word — confirm with your building department.