how far can a 2×8 span

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, or 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 SPF (spruce-pine-fir) lumber.
  • 13 feet 5 inches for #2 DF (Douglas fir) lumber.

• 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 SPF lumber.
  • 11 feet 5 inches for #2 DF 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 SPF lumber.
  • 16 feet 5 inches for #2 DF 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 SPF lumber.
  • 14 feet 5 inches for #2 DF lumber.

Ceiling Joists:

• For a residential ceiling with a 10 psf live load and a 5 psf dead load, a 2×8 beam can span:

  • 16 feet 8 inches for #2 SPF lumber.
  • 18 feet 5 inches for #2 DF lumber.

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.