Load Duration

The load duration factor stems from the fact that wood is strongest when loaded for a short time. Design properties are typically based on the assumption that the load will be on the structure for a "normal" period of time. Some loads such as wind loads do not occur at full intensity except for a relatively short period of time. Since the duration of the wind load is shorter than the assumed basis for normal design values, some design properties may be increased by a duration factor. Typical load duration factors are noted below:

• 100% Floor Live Load

• 115% or 100% Roof Snow Load

• 125% Roof Construction Live Load

• 160% Wind or Quake Live Load