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Depending on various factors, the maximum span for a 2×8 floor joist is 16′ 6”. The maximum span for roof rafters is 23′ 9”. For headers, the maximum span is 11′ 2”.

## How far can a rafter span without support?

A 2×6 spaced 16 inches apart can span a maximum distance of 13 feet 5 inches when used as a rafter, 10 feet 9 inches when used as a joist, and 6 feet 11 inches when used as a deck beam to support joists with a 6-foot span.

## How far can a 2×10 Rafter span without support?

A 2×10 beam – made up of two 2x10s nailed together – can span up to 11′ without support beneath a deck that is 4′ wide. For a more normal-sized deck, the same beam can span 8′, supporting a deck that is 8′ wide.

## Can a 2×8 span 16 feet?

Span is determined by species, grade, dimensions, spacing, use, and load. A rule of thumb is 1.5 times a joist’s depth but in feet when spaced at 16” centers. In general, a 2×8 will span 1.5 x 8, so 12-feet. Based on all factors though, a 2×8 joist span is 7′-1” to 16′-6”, and a rafter 6′-7” and 23′-9”.

## How far apart should rafters be?

But they do tend to space rafters in one of several industry-standard increments, typically either 12, 16 or 24 inches apart. These spacing intervals are measured “on center,” meaning that the measurement is taken from the center of one rafter’s horizontal surface to the center of the next rafter.

## What size lumber can span 16 feet?

Max. Live Load 30 lbs/ft2 (1436 N/m2)

Maximum Span (ft – in) | ||
---|---|---|

Nominal Size (inches) | Joist Spacing Center to Center (inches) | Lumber Grade |

2 x 6 | 24 | 9′ – 11″ |

2 x 8 | 12 | 16′ – 6″ |

16 | 15′ – 0″ |

## How far will a 4×8 Rafter span?

lists 14’6″ as the max allowable span for 4×8 rafter.

## What size should roof rafters be?

Use these two tables for roof rafters with a slope greater than 3″ in 12″.

Nominal Size | Spaced (o.c.) | Species / Grade ( 20# Live Load – Light Roofing) |
---|---|---|

2″ x 6″ | 12 | 18-1 |

16 | 16-4 | |

24 | 13-4 | |

2″ x 8″ | 12 | 23-8 |

## How much load can a 2X8 support?

The weight that can be supported by a double or triple wood header

Span (feet) | Weight Supported (lb) | |
---|---|---|

2 x 2″ x 6″ | 2 x 2″ x 8″ | |

4 | 2250 | 4690 |

6 | 1680 | 3130 |

8 | 2660 |

## What size beam do I need to span 12 feet?

A double ply beam can span in feet if there is no overhang beyond it. A double 2×12 beam can span 12 feet, a double 2×10 can span 10 feet, and so on.

## How do you calculate rafter length?

If you are calculating rafter length from the center of the ridge beam (as shown below), you will need to subtract half of the thickness of the ridge beam from the top end of the rafter. For example, if the ridge beam is 1.5 inches thick, subtract 3/4 of an inch from the overall rafter length.

## How wide can rafters span?

For light load roofs, 24” o.c. 2×4 rafters can span up to 7 ⅔’. For heavy loads, 2x4s can span up to 5 ½’. Most roof framing is 24” on center, and you can still build sheds up to 14′ with 2×4 rafters at 24” on center.

## How do you calculate beam span on a roof?

How to Size a Beam to Hold a Porch Roof

- Determine the load per square foot that the roof must support. …
- Multiply the load per square foot by the total area of the roof. …
- Divide the total load according to how many supporting beams the roof will have. …
- Write down the beam strength formula: Total load in pounds = FBd^2 / 9L.