There are two standard I-beam forms:
Rolled I-beam, formed by hot rolling, cold rolling or extrusion, depending on the material.
Plate girder, formed by welding (or occasionally bolting or riveting) plates.
I-beams are commonly made of structural steel but may also be formed from aluminium or other materials. A common type of I-beam is the rolled steel joist (RSJ), sometimes incorrectly rendered as reinforced steel joist. British and European standards also specify Universal Beams (UBs) and Universal Columns (UCs). These sections have parallel flanges, shown as "W-Section" in the accompanying illustration, as opposed to the varying thickness of RSJ flanges, illustrated as "S-Section", which are seldom now rolled in the United Kingdom. Parallel flanges are easier to connect to and do away with the need for tapering washers. UCs have equal or near-equal width and depth and are more suited to being oriented vertically to carry axial load such as columns in multi-storey construction, while UBs are significantly deeper than they are wide are more suited to carrying bending load such as beam elements in floors.
I-joists, I-beams engineered from wood with fiberboard or laminated veneer lumber, or both, are also becoming increasingly popular in construction, especially residential, as they are both lighter and less prone to warping than solid wooden joists. However, there has been some concern as to their rapid loss of strength in a fire if unprotected.
