What Is Beam Span?

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  • Written By: Troy Holmes
  • Edited By: W. Everett
  • Last Modified Date: 04 October 2019
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Beams are an important structural device used to support buildings, bridges, and decks. Beam span is the maximum length allowed for a beam to adequately support a specific weighted area. This span is different for each type of beam material and is based on the dimensions of the beam. Thicker beams can have a longer span than thinner beams.

Beam span charts are used in the construction industry to determine the appropriate length of beams for specific building applications. Building inspectors use these charts to determine the minimum load requirements for beams. Beam spans should not be overloaded because this could cause an unsafe condition in the building structure.

The beam span is different for each type of material. A steal beam is heavier then a wooden beam and can support a larger loaded surface area. These beams are typically used for supporting homes and bridges, but have a limited span based on the weight of the structure being supported.

An I-beam is a beam shaped like an H that is used to support the main floor of a home or building. This type of beam is normally made from steel and has a specific length and width based on the size of the home. The beam span for I-beams varies based on the width, height, and thickness of the steel beam.


Deck beams are the beams that hold the floor boards for decks. The beam span for most deck beams is less then 16 feet (4.87 meters) but can be as small as 8 feet (4.87 meters) depending on the thickness of the beam. These special beams support the weight of the main floor on the deck are an essential for overall structural integrity.

Having a beam span that is heavier then necessary can be costly for the homeowner or builder. It is important to review the appropriate requirements for each building application. This ensures a structure is safe without being unnecessarily costly.

Beam bridges are special bridges made from either wood or steel beams. As the beams become farther apart, the bridge structure weakens. That is why most beam bridges are made from multiple beam units that are joined together to make a continuous spanning bridge.

Concrete beam span is typically used on national highways and bridges. These concrete structures support large multi-lane roads. A concrete girder bridge is an example of a concrete bridge that has specific spans for each arm. These special beams can support spans more then 150 feet (45.72 meters) long.


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