How far apart should rafters be?
Answer
The permitted spacing depends on rafter size, lumber species, grade, span, loads, and local requirements.
Use the approved plans or an applicable span table to select the maximum spacing.
| Maximum spacing | Positions on each side | Gable rafters | Calculated spacing |
|---|---|---|---|
| 12 in | 31 | 62 | 12.00 in |
| 16 in | 24 | 48 | 15.65 in |
| 24 in | 16 | 32 | 24.00 in |
The table calculates quantity only. The table does not approve structural spacing.
Select the maximum spacing
Use the project plans when they give a rafter spacing. Use that spacing as the maximum.
The AWC span calculator includes species, grade, loads, spacing, and deflection limits.
Calculate equal spaces
- Divide the roof length by the maximum spacing.
- If the result is not whole, increase it to the next whole number.
- Add one position.
- Divide the roof length by the whole space quantity.
Count both roof sides
Multiply the position quantity by two for a simple gable roof. A single-slope roof has one row of positions.
Use the rafter calculator to calculate the positions and stock quantity.
Important information
- Use approved plans or an applicable span table for the maximum spacing.
- Calculate openings, hips, valleys, and gable-end framing separately.
- Obey the approved plans and local requirements.