Standard span tables describe the properties of straight beams. Specialty tables contain information about arches, columns and curved beams. Another table helps engineers make architecturally viable substitutions for unavailable materials.
Span tables contain important information about the maximum construction load and live load for a given beam. The construction load, or dead load, is the weight of structural materials. The live load refers to the weight of people and objects. Some span tables, such as those published by the American Institute of Timber Construction, also indicate maximum snow load capacity. Snow load refers to the weight of accumulated snow and ice.
Structural engineers use span tables to choose wooden beams that comply with local building codes. The codes dictate the acceptable load ranges for joists and rafter beams. Engineers use this information to determine the beams' required size, strength, and flexibility. Comparing these figures with the span table helps engineers and architects select a wood species and grade that conforms to the project budget.
