If you’re using a 2×4 simple wood ceiling joist, you can span it from 4 to 12 feet. The exact span for a ceiling joist depends on factors like type and grade of lumber, the spacing, the load. Normal spacing of ceiling joist is 16 inches or 24 inches on center.
Ceiling joist is a structural framing member which is used to support the ceiling of house and anything which is mounted on the ceiling such as light fixtures, smoke alarms, fire sprinkler system, air vents etc. The ceiling joists are designed to carry the load of all these attachments and to carry their own weight too.
Ceiling joists are critical member of house structure. They not only support the weight of ceiling but also bear the outward pressure that is placed on exterior walls from roof.
Also Read: How far can you span with flitch beam? (Design with online calculator)
While designing the size and length of joists used for framing the ceiling depends upon the design loads which are dead loads and live loads. The other factor which decide the size and length of joist is material type used for joist.
Table of Contents
- Factors effecting span of a ceiling joist
- Ceiling Joist span Table
- How far apart you can span a 2” ×4” ceiling joist
- How far apart you can span a 2” ×6” ceiling joist
- How far apart you can span a 2” ×8” ceiling joist
- Conclusion
Factors effecting span of a ceiling joist
The standard construction of interior framing use 16 inch on center spacing for ceiling joists.
- Joist Spacing: The spacing can also be reduced to 12 inches on center or can be increased to 24 inches on center depending upon the span length, quality and type of lumber. The increase in joist spacing results in decreasing the span length of joist.
- Wood Species: There are different species of woods such as southern yellow pine, Douglas fir and hemlock fir. These species of woods are made of different grades such as grade 1, grade 2, grade 3. The southern pine strongest type of wood as compared to other species of woods. The quality of grade 1 southern pine is good and have higher strength than other grade lumber due to less knots.
The most commonly used size of joist for framing are 2” ×4”, 2” ×6”, 2” ×8” and 2” ×10”. The size of joist used for framing depends on the design loads, span length, grade and type of wood.
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In this article we will discuss how far all these sizes of joists made of different types of woods can be placed.
Ceiling Joist span Table
| Nominal Size | Spaced (O.C) | Species/Grade | ||
| Southern Pine | Douglas Fir | Hemlock fir | ||
| #2 grade | #2 grade | #2 grade | ||
| 2″ x 4″ | 12 | 11-10 | 12-5 | 11-7 |
| 16 | 10-9 | 11-3 | 10-6 | |
| 24 | 9-3 | 9-10 | 9-2 | |
| 2″ x 6″ | 12 | 18-8 | 19-6 | 18-2 |
| 16 | 16-11 | 17-8 | 16-6 | |
| 24 | 13-11 | 15-0 | 14-5 | |
| 2″ x 8″ | 12 | 24-7 | 25-8 | 24-0 |
| 16 | 21-7 | 23-4 | 21-9 | |
| 24 | 17-7 | 19-1 | 18-6 | |
| 2″ x 10″ | 12 | ** | ** | ** |
| 16 | 25-7 | ** | ** | |
| 24 | 20-11 | 23-3 | 22-7 | |
How far apart you can span a 2” ×4” ceiling joist
The 2” ×4” size joist with dead load of 5 psf and live load of 10 psf and made of southern pine of grade 2 can span up to 11 feet and 10 inches with on spacing 12”. Similarly, the joist of same size with same design loads and made of southern pine of grade 2 can span up to 10 feet and 9 inches with on spacing 16 inches.
- Size of ceiling joist= 2” ×4”
- Grade of joist = #2
- Span Length = 11’ and 10”
- On spacing (OC)= 12 “
- Size of ceiling joist= 2” ×4”
- Grade of joist = #2
- Span Length = 9’ and 3”
- On spacing (OC)= 24 “
How far apart you can span a 2” ×6” ceiling joist
The 2” ×6” size joist for ceiling dead load of 5 psf and live load of 10 psf and made of southern pine of grade 2 can span up to 18 feet and 8 inches with on spacing 12”. Similarly, the joist of same size with same ceiling loads and made of southern pine of grade 2 can span up to 16 feet and 11 inches with on spacing of 16 inches.
- Size of ceiling joist= 2” ×6”
- Grade of joist = #2
- Span Length = 18’ and 8”
- On spacing (OC)= 12 “
- Size of ceiling joist= 2” ×6”
- Grade of joist = #2
- Span Length = 16’ and 11”
- On spacing (OC)= 16 “
- Size of ceiling joist= 2” ×6”
- Grade of joist = #2
- Span Length = 13’ and 11”
- On spacing (OC)= 24 “
How far apart you can span a 2” ×8” ceiling joist
The 2” ×8” size joist with dead load of 5 psf and live load of 10 psf and made of southern pine of grade 2 can span up to 18 feet and 8 inches with on spacing 12”. Similarly, the joist of same size with same design loads and made of southern pine of grade 2 can span up to 16 feet and 11 inches with on spacing 16 inches.
- Size of ceiling joist= 2” ×8”
- Grade of joist = #2
- Span Length = 18’ and 8”
- On spacing (OC)= 12 “
- Size of ceiling joist= 2” ×8”
- Grade of joist = #2
- Span Length = 16’ and 11”
- On spacing (OC)= 16 “
- Size of ceiling joist= 2” ×8”
- Grade of joist = #2
- Span Length = 13’ and 11”
- On spacing (OC)= 24 “
The smaller size of joist can be used for small span length with suitable spacing of joist with smaller design loads. As the span length and design loads starts increasing the size of joist also increased and spacing between the joists decreases.
Also Read: Floor joist Span – How far can you span a 2×6, 2×8, 2×10 & 2×12
Conclusion
The ceiling joist is important framing member which support ceiling and other fixtures load. The spacing between the joists depends upon the size of joist, type of lumber, grade of wood and span length. As the span length is increased then size of joist will be increased and spacing will decrease for joists.
