2×4 ceiling joist spans (2021 IRC)
Every allowable span the 2021 International Residential Code ceiling tables list for a 2×4 joist — four species, four grades, four spacings, both attic load cases — each table cited where it sits.
2021 IRC Table R802.5.1(2) covers uninhabitable attics with limited storage; 2021 IRC Table R802.5.1(1) covers uninhabitable attics without storage. Both tables are below, in that order.
A 2×4 Southern pine No. 2 ceiling joist at 16-inch centers spans up to 8’0” in an uninhabitable attic with limited storage (2021 IRC Table R802.5.1(2)). Widen the spacing to 24-inch centers and the same joist is listed at 6’7”; hold 16-inch centers and switch to Spruce-pine-fir No. 2 and the table lists 8’7”. Under 2021 IRC Table R802.5.1(1) — uninhabitable attics without storage, 10 psf live / 5 psf dead / L/240 — that same Southern pine No. 2 at 16 inches is listed at 10’9”.
2×4 ceiling joists — uninhabitable attics with limited storage
| 2×4 — species and grade | 12" on center | 16" on center | 19.2" on center | 24" on center |
|---|---|---|---|---|
| Douglas fir-larch Select Structural | 10’5” | 9’6” | 8’11” | 8’3” |
| Douglas fir-larch No. 1 | 10’0” | 9’1” | 8’7” | 7’8” |
| Douglas fir-larch No. 2 | 9’10” | 8’11” | 8’2” | 7’3” |
| Douglas fir-larch No. 3 | 7’10” | 6’10” | 6’2” | 5’7” |
| Hem-fir Select Structural | 9’10” | 8’11” | 8’5” | 7’10” |
| Hem-fir No. 1 | 9’8” | 8’9” | 8’3” | 7’7” |
| Hem-fir No. 2 | 9’2” | 8’4” | 7’10” | 7’1” |
| Hem-fir No. 3 | 7’8” | 6’8” | 6’1” | 5’5” |
| Southern pine Select Structural | 10’3” | 9’4” | 8’9” | 8’1” |
| Southern pine No. 1 | 9’10” | 8’11” | 8’5” | 7’8” |
| Southern pine No. 2 | 9’3” | 8’0” | 7’4” | 6’7” |
| Southern pine No. 3 | 7’2” | 6’2” | 5’8” | 5’1” |
| Spruce-pine-fir Select Structural | 9’8” | 8’9” | 8’3” | 7’8” |
| Spruce-pine-fir No. 1 | 9’5” | 8’7” | 8’0” | 7’2” |
| Spruce-pine-fir No. 2 | 9’5” | 8’7” | 8’0” | 7’2” |
| Spruce-pine-fir No. 3 | 7’8” | 6’8” | 6’1” | 5’5” |
2021 IRC Table R802.5.1(2) — uninhabitable attics with limited storage, 20 psf live / 10 psf dead / L/240. table source
2×4 ceiling joists — uninhabitable attics without storage
| 2×4 — species and grade | 12" on center | 16" on center | 19.2" on center | 24" on center |
|---|---|---|---|---|
| Douglas fir-larch Select Structural | 13’2” | 11’11” | 11’3” | 10’5” |
| Douglas fir-larch No. 1 | 12’8” | 11’6” | 10’10” | 10’0” |
| Douglas fir-larch No. 2 | 12’5” | 11’3” | 10’7” | 9’10” |
| Douglas fir-larch No. 3 | 11’1” | 9’7” | 8’9” | 7’10” |
| Hem-fir Select Structural | 12’5” | 11’3” | 10’7” | 9’10” |
| Hem-fir No. 1 | 12’2” | 11’0” | 10’4” | 9’8” |
| Hem-fir No. 2 | 11’7” | 10’6” | 9’11” | 9’2” |
| Hem-fir No. 3 | 10’10” | 9’5” | 8’7” | 7’8” |
| Southern pine Select Structural | 12’11” | 11’9” | 11’0” | 10’3” |
| Southern pine No. 1 | 12’5” | 11’3” | 10’7” | 9’10” |
| Southern pine No. 2 | 11’10” | 10’9” | 10’2” | 9’3” |
| Southern pine No. 3 | 10’1” | 8’9” | 8’0” | 7’2” |
| Spruce-pine-fir Select Structural | 12’2” | 11’0” | 10’4” | 9’8” |
| Spruce-pine-fir No. 1 | 11’10” | 10’9” | 10’2” | 9’5” |
| Spruce-pine-fir No. 2 | 11’10” | 10’9” | 10’2” | 9’5” |
| Spruce-pine-fir No. 3 | 10’10” | 9’5” | 8’7” | 7’8” |
2021 IRC Table R802.5.1(1) — uninhabitable attics without storage, 10 psf live / 5 psf dead / L/240. table source
The two attic cases
2021 IRC Table R802.5.1(1) is the uninhabitable attics without storage case: 10 psf live over 5 psf dead, L/240. 2021 IRC Table R802.5.1(2) is the uninhabitable attics with limited storage case: 20 psf live over 10 psf dead, L/240. The dead load is the part that gets skipped — 5 psf where the attic holds no storage, 10 psf where the table allows limited storage — and it is why the same 2×4 carries two different spans on this page.
Each number is the span the code table lists for that species, grade, and on-center spacing at the load case stamped at the top of this page. Change the spacing, the grade, or the species and you are reading a different cell of the same table.
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.
Other sizes and assemblies
Other ceiling joist sizes: 2×6 ceiling joists · 2×8 ceiling joists · 2×10 ceiling joists
The same 2×4 in other assemblies: 2×4 rafters
Common questions
Can 2×4 ceiling joists span 11 feet?
At 16-inch centers, 2×4 Southern pine No. 2 is listed at 8’0” in 2021 IRC Table R802.5.1(2) (20 psf live / 10 psf dead / L/240). No 2×4 cell in that table reaches 11 feet — the longest listed is 10’5”, Douglas fir-larch Select Structural at 12-inch centers.
Do these 2×4 ceiling joist spans allow attic storage?
Two cases, two tables. 2021 IRC Table R802.5.1(1) is the uninhabitable attics without storage case — 10 psf live over 5 psf dead at L/240 — and lists 2×4 Southern pine No. 2 at 16-inch centers at 10’9”. 2021 IRC Table R802.5.1(2) is the uninhabitable attics with limited storage case — 20 psf live over 10 psf dead at L/240 — and lists the same joist at 8’0”.
How far can a 2×4 ceiling joist span at 24-inch centers?
2021 IRC Table R802.5.1(2) — uninhabitable attics with limited storage — lists 2×4 No. 2 at 24-inch centers as Douglas fir-larch 7’3”, Hem-fir 7’1”, Southern pine 6’7”, Spruce-pine-fir 7’2”. The same four in 2021 IRC Table R802.5.1(1) (uninhabitable attics without storage): 9’10”, 9’2”, 9’3”, 9’5”.