how far can you span 2×8

The maximum span for a 2×8 beam depends on several factors, including:

1. Load: The weight and type of load being supported (e.g., roof, floor, wall).
2. Species and grade of lumber: Different types of wood have varying strength and stiffness properties.
3. Orientation: Whether the beam is used as a joist (horizontal) or a rafter (angled).
4. Spacing: The distance between adjacent beams.

Here are some general guidelines for maximum spans for 2×8 beams:

Floor Joists:

• For a residential floor with a 40 psf (pounds per square foot) live load and a 10 psf dead load, a 2×8 beam can span:

  • 12 feet 8 inches for #2 grade lumber (e.g., spruce-pine-fir).
  • 14 feet 5 inches for #1 grade lumber (e.g., Douglas fir-larch).

• For a commercial floor with a 50 psf live load and a 20 psf dead load, a 2×8 beam can span:

  • 10 feet 8 inches for #2 grade lumber.
  • 12 feet 5 inches for #1 grade lumber.

Roof Rafters:

• For a residential roof with a 20 psf live load and a 10 psf dead load, a 2×8 beam can span:

  • 14 feet 8 inches for #2 grade lumber.
  • 16 feet 5 inches for #1 grade lumber.

• For a commercial roof with a 30 psf live load and a 20 psf dead load, a 2×8 beam can span:

  • 12 feet 8 inches for #2 grade lumber.
  • 14 feet 5 inches for #1 grade lumber.

Headers:

• For a header supporting a roof or floor load, a 2×8 beam can span:

  • 8 feet for a single-ply header (one 2×8 beam).
  • 12 feet for a double-ply header (two 2×8 beams).

Keep in mind that these are general guidelines and may not apply to your specific situation. It’s always best to consult with a structural engineer or a qualified builder to determine the maximum span for a 2×8 beam in your particular project.