how far can a 2×8 span without support

The distance a 2×8 can span without support depends on several factors, including:

1. Load: The weight and type of load it will be carrying (e.g., roof, floor, wall).
2. Grade: The type and quality of the lumber (e.g., #1, #2, or construction grade).
3. Orientation: Whether the 2×8 is used as a joist (horizontal) or a rafter (angled).
4. Building codes: Local building codes and regulations may dictate specific span limits.

Here are some general guidelines for 2×8 spans:

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 can span:

  • 12 feet 8 inches (3.86 meters) for #1 grade lumber.
  • 11 feet 9 inches (3.58 meters) for #2 grade lumber.

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

  • 10 feet 8 inches (3.25 meters) for #1 grade lumber.
  • 9 feet 9 inches (2.97 meters) for #2 grade lumber.

Roof Rafters:

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

  • 14 feet 8 inches (4.47 meters) for #1 grade lumber.
  • 13 feet 4 inches (4.06 meters) for #2 grade lumber.

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

  • 12 feet 2 inches (3.71 meters) for #1 grade lumber.
  • 11 feet 1 inch (3.38 meters) for #2 grade lumber.

Ceiling Joists:

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

  • 16 feet 8 inches (5.08 meters) for #1 grade lumber.
  • 15 feet 2 inches (4.62 meters) for #2 grade lumber.

Keep in mind that these are general estimates and may vary depending on specific conditions. It’s always best to consult with a structural engineer or a local building authority to determine the maximum span for a 2×8 in your specific situation.