A ceiling joist span chart gives the maximum span for a ceiling joist of a given size, species, grade, and spacing, based on how the attic above is used. Under 2021 IRC Table R802.5.1(1) (attic without storage), a #2 Douglas fir-larch ceiling joist at 16" o.c. spans 11'-3" as a 2x4, 17'-8" as a 2x6, and 23'-4" as a 2x8.
The charts below are copied from the 2021 International Residential Code. Each applies only to the load case in its caption, and your adopted code and local amendments govern. Ceiling joists usually sit under rafters, so they are one part of the roof framing plan rather than a separate drawing.
Two ceiling joist tables, chosen by attic use
The IRC sizes ceiling joists from two tables. The choice depends entirely on what the attic above is used for.
| Table | Attic use | Live load | Dead load | Deflection |
|---|---|---|---|---|
| R802.5.1(1) | Uninhabitable, without storage | 10 psf | 5 psf | L/240 |
| R802.5.1(2) | Uninhabitable, with limited storage | 20 psf | 10 psf | L/240 |
The difference is large. Doubling the live load and the dead load takes several feet off every span. The IRC defines what counts as limited storage alongside its live load table in Chapter 3, so check those footnotes in your adopted code before choosing the lighter table. If the attic is reached by a fixed stairway, it is no longer a ceiling: Section R502.3.1 sends it to floor joist Table R502.3.1(1), covered in the floor joist span table.
How to read a ceiling joist span chart
The inputs are the same as any lumber span table:
- Species and grade from the grade stamp. The charts here use #2.
- Spacing, 12, 16, 19.2, or 24 inches on center. Floor joist spacing explained covers how on-center spacing works, and it is identical for ceiling joists.
- Span, the clear horizontal distance between the supports the joist bears on, such as an exterior wall and an interior partition.
"Over 26'" in the charts is the table's note a: the span exceeds 26 feet. The tables also note that lumber longer than 20 feet may be hard to get, so check supply before relying on those long values.
Ceiling joist span chart: attics without storage
2021 IRC Table R802.5.1(1): #2 grade, uninhabitable attics without storage, live load 10 psf, dead load 5 psf, L/Δ = 240. Maximum ceiling joist spans in feet-inches.
| Species and spacing | 2x4 | 2x6 | 2x8 | 2x10 |
|---|---|---|---|---|
| Douglas fir-larch @ 12" | 12'-5" | 19'-6" | 25'-8" | Over 26' |
| Douglas fir-larch @ 16" | 11'-3" | 17'-8" | 23'-4" | Over 26' |
| Douglas fir-larch @ 19.2" | 10'-7" | 16'-8" | 21'-4" | 26'-0" |
| Douglas fir-larch @ 24" | 9'-10" | 15'-0" | 19'-1" | 23'-3" |
| Hem-fir @ 12" | 11'-7" | 18'-2" | 24'-0" | Over 26' |
| Hem-fir @ 16" | 10'-6" | 16'-6" | 21'-9" | Over 26' |
| Hem-fir @ 19.2" | 9'-11" | 15'-7" | 20'-6" | 25'-3" |
| Hem-fir @ 24" | 9'-2" | 14'-5" | 18'-6" | 22'-7" |
| Southern pine @ 12" | 11'-10" | 18'-8" | 24'-7" | Over 26' |
| Southern pine @ 16" | 10'-9" | 16'-11" | 21'-7" | 25'-7" |
| Southern pine @ 19.2" | 10'-2" | 15'-7" | 19'-8" | 23'-5" |
| Southern pine @ 24" | 9'-3" | 13'-11" | 17'-7" | 20'-11" |
| Spruce-pine-fir @ 12" | 11'-10" | 18'-8" | 24'-7" | Over 26' |
| Spruce-pine-fir @ 16" | 10'-9" | 16'-11" | 22'-4" | Over 26' |
| Spruce-pine-fir @ 19.2" | 10'-2" | 15'-11" | 21'-0" | 25'-8" |
| Spruce-pine-fir @ 24" | 9'-5" | 14'-9" | 18'-9" | 22'-11" |
Ceiling joist span chart: attics with limited storage
2021 IRC Table R802.5.1(2): #2 grade, uninhabitable attics with limited storage, live load 20 psf, dead load 10 psf, L/Δ = 240. Maximum ceiling joist spans in feet-inches.
| Species and spacing | 2x4 | 2x6 | 2x8 | 2x10 |
|---|---|---|---|---|
| Douglas fir-larch @ 12" | 9'-10" | 15'-0" | 19'-1" | 23'-3" |
| Douglas fir-larch @ 16" | 8'-11" | 13'-0" | 16'-6" | 20'-2" |
| Douglas fir-larch @ 19.2" | 8'-2" | 11'-11" | 15'-1" | 18'-5" |
| Douglas fir-larch @ 24" | 7'-3" | 10'-8" | 13'-6" | 16'-5" |
| Hem-fir @ 12" | 9'-2" | 14'-5" | 18'-6" | 22'-7" |
| Hem-fir @ 16" | 8'-4" | 12'-8" | 16'-0" | 19'-7" |
| Hem-fir @ 19.2" | 7'-10" | 11'-7" | 14'-8" | 17'-10" |
| Hem-fir @ 24" | 7'-1" | 10'-4" | 13'-1" | 16'-0" |
| Southern pine @ 12" | 9'-3" | 13'-11" | 17'-7" | 20'-11" |
| Southern pine @ 16" | 8'-0" | 12'-0" | 15'-3" | 18'-1" |
| Southern pine @ 19.2" | 7'-4" | 11'-0" | 13'-11" | 16'-6" |
| Southern pine @ 24" | 6'-7" | 9'-10" | 12'-6" | 14'-9" |
| Spruce-pine-fir @ 12" | 9'-5" | 14'-9" | 18'-9" | 22'-11" |
| Spruce-pine-fir @ 16" | 8'-7" | 12'-10" | 16'-3" | 19'-10" |
| Spruce-pine-fir @ 19.2" | 8'-0" | 11'-9" | 14'-10" | 18'-2" |
| Spruce-pine-fir @ 24" | 7'-2" | 10'-6" | 13'-3" | 16'-3" |
2x4, 2x6, and 2x8 ceiling joist spans at 16 inches on center
The quick answers most people search for, #2 grade at 16" o.c.:
| Size | Without storage, Table R802.5.1(1) | Limited storage, Table R802.5.1(2) |
|---|---|---|
| 2x4 | 10'-6" to 11'-3" | 8'-0" to 8'-11" |
| 2x6 | 16'-6" to 17'-8" | 12'-0" to 13'-0" |
| 2x8 | 21'-7" to 23'-4" | 15'-3" to 16'-6" |
| 2x10 | 25'-7" to over 26' | 18'-1" to 20'-2" |
The low end of each range is hem-fir or Southern pine and the high end is Douglas fir-larch, so the species on the stamp matters. A 2x6 that spans a 16-foot room with an empty attic above falls short once that attic holds stored boxes.
Ceiling joists also tie the roof together
On a stick-framed gable roof, ceiling joists do a second job: they act as ties that stop the rafters pushing the walls apart. Section R802.5 requires ceiling joists to be continuous across the structure or securely joined where they meet over interior partitions. Section R802.5.2 adds:
- Where ceiling joists run parallel to the rafters and sit in the bottom third of the rafter height, they are fastened to the rafters using the heel joint connections in Table R802.5.2(1).
- Where ceiling joists sit above the bottom third, the ridge must be designed as a beam.
- Where ceiling joists do not run parallel to the rafters, the rafters need rafter ties, or the ridge must be designed as a beam.
So the direction you draw ceiling joists on the plan is a structural decision, not just a layout preference. The rafter span chart covers the rafters themselves and the span reduction when ties sit higher in the attic, and ridge beam vs ridge board explains why the ridge changes.
What the chart does not cover
- Trusses and engineered lumber. Roof trusses carry the ceiling on their bottom chord and are designed by the truss manufacturer. I-joists and LVL use manufacturer tables. See rafters vs trusses.
- Equipment and point loads. An air handler, water heater, or attic platform is a concentrated load the uniform tables do not address.
- Other species, grades, or loads. Section R802.5.1 points these to the AWC Span Tables for Joists and Rafters, available from the American Wood Council.
Drawing ceiling joists on the plan
Label ceiling joists like any joist field: size, grade, spacing, and direction, such as 2x6 #2 SPF CEILING JOISTS @ 16" O.C., with a note stating which attic-use table you assumed. The same callout habits apply as on a floor framing plan.
Framing Plan draws joist layouts, beams, and openings and exports PNG, PDF, and DXF. It does not check spans against these IRC tables: the bundled sample profile uses demo span figures and metric member sizes, and the editor authors in millimeters. Size from the code table, then open the framing studio to draw a preliminary layout for your designer or plan reviewer.