2×8 ceiling joist spans (2021 IRC)
Every allowable span the 2021 International Residential Code ceiling tables list for a 2×8 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 2×8 Southern pine No. 2 ceiling joist at 16-inch centers spans up to 15’3” 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 12’6”; hold 16-inch centers and switch to Spruce-pine-fir No. 2 and the table lists 16’3”. 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 21’7”.
2×8 ceiling joists — uninhabitable attics with limited storage
| 2×8 — species and grade | 12" on center | 16" on center | 19.2" on center | 24" on center |
|---|---|---|---|---|
| Douglas fir-larch Select Structural | 21’7” | 19’7” | 18’5” | 17’2” |
| Douglas fir-larch No. 1 | 20’1” | 17’5” | 15’10” | 14’2” |
| Douglas fir-larch No. 2 | 19’1” | 16’6” | 15’1” | 13’6” |
| Douglas fir-larch No. 3 | 14’7” | 12’7” | 11’6” | 10’3” |
| Hem-fir Select Structural | 20’5” | 18’6” | 17’5” | 16’2” |
| Hem-fir No. 1 | 19’10” | 17’2” | 15’8” | 14’0” |
| Hem-fir No. 2 | 18’6” | 16’0” | 14’8” | 13’1” |
| Hem-fir No. 3 | 14’2” | 12’4” | 11’3” | 10’0” |
| Southern pine Select Structural | 21’2” | 19’3” | 18’2” | 16’10” |
| Southern pine No. 1 | 20’5” | 17’9” | 16’2” | 14’6” |
| Southern pine No. 2 | 17’7” | 15’3” | 13’11” | 12’6” |
| Southern pine No. 3 | 13’3” | 11’6” | 10’6” | 9’5” |
| Spruce-pine-fir Select Structural | 19’11” | 18’1” | 17’1” | 15’10” |
| Spruce-pine-fir No. 1 | 18’9” | 16’3” | 14’10” | 13’3” |
| Spruce-pine-fir No. 2 | 18’9” | 16’3” | 14’10” | 13’3” |
| Spruce-pine-fir No. 3 | 14’2” | 12’4” | 11’3” | 10’0” |
2021 IRC Table R802.5.1(2) — uninhabitable attics with limited storage, 20 psf live / 10 psf dead / L/240. table source
2×8 ceiling joists — uninhabitable attics without storage
| 2×8 — species and grade | 12" on center | 16" on center | 19.2" on center | 24" on center |
|---|---|---|---|---|
| Douglas fir-larch Select Structural | 26’+ | 24’8” | 23’3” | 21’7” |
| Douglas fir-larch No. 1 | 26’+ | 23’10” | 22’5” | 20’1” |
| Douglas fir-larch No. 2 | 25’8” | 23’4” | 21’4” | 19’1” |
| Douglas fir-larch No. 3 | 20’7” | 17’10” | 16’3” | 14’7” |
| Hem-fir Select Structural | 25’8” | 23’4” | 21’11” | 20’5” |
| Hem-fir No. 1 | 25’2” | 22’10” | 21’6” | 19’10” |
| Hem-fir No. 2 | 24’0” | 21’9” | 20’6” | 18’6” |
| Hem-fir No. 3 | 20’1” | 17’5” | 15’10” | 14’2” |
| Southern pine Select Structural | 26’+ | 24’3” | 22’10” | 21’2” |
| Southern pine No. 1 | 25’8” | 23’10” | 22’0” | 20’5” |
| Southern pine No. 2 | 24’7” | 21’7” | 19’8” | 17’7” |
| Southern pine No. 3 | 18’9” | 16’3” | 14’10” | 13’3” |
| Spruce-pine-fir Select Structural | 25’2” | 22’10” | 21’6” | 19’11” |
| Spruce-pine-fir No. 1 | 24’7” | 22’4” | 21’0” | 18’9” |
| Spruce-pine-fir No. 2 | 24’7” | 22’4” | 21’0” | 18’9” |
| Spruce-pine-fir No. 3 | 20’1” | 17’5” | 15’10” | 14’2” |
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 2×8 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: 2×4 ceiling joists · 2×6 ceiling joists · 2×10 ceiling joists
The same 2×8 in other assemblies: 2×8 floor joists · 2×8 rafters · 2×8 deck joists
Common questions
Can 2×8 ceiling joists span 18 feet?
At 16-inch centers, 2×8 Southern pine No. 2 is listed at 15’3” in 2021 IRC Table R802.5.1(2) (20 psf live / 10 psf dead / L/240). 17 of the 64 2×8 cells in that table are 18 feet or longer, and the widest spacing among them is 19.2-inch centers — Southern pine Select Structural at 19.2 inches is listed at 18’2”.
Do these 2×8 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 2×8 Southern pine No. 2 at 16-inch centers at 21’7”. 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 15’3”.
How far can a 2×8 ceiling joist span at 24-inch centers?
2021 IRC Table R802.5.1(2) — uninhabitable attics with limited storage — lists 2×8 No. 2 at 24-inch centers as Douglas fir-larch 13’6”, Hem-fir 13’1”, Southern pine 12’6”, Spruce-pine-fir 13’3”. The same four in 2021 IRC Table R802.5.1(1) (uninhabitable attics without storage): 19’1”, 18’6”, 17’7”, 18’9”.