S12x31.8 – S Shapes - American standard beams

S12x31.8 is 12 in (305 mm) deep with a 5 in (127 mm) wide flange, and weighs 31.8 lb/ft (47.3 kg/m).

S shapes (American Standard Beams) are the older of the two common I-beam families — predecessors to the W shape — recognizable by their tapered (sloped) inner flange faces, unlike the parallel flange faces of a W shape. Depth-for-depth, S shapes generally have narrower flanges than their W counterparts, a proportion that suits specific applications: crane rails and monorail beams, machinery and equipment supports, and retrofit or replacement work on existing structures originally built with S shapes. While W shapes have become the default choice for new general framing, S shapes remain in production and in demand wherever a design specifically calls for their narrower-flange proportions or a project needs to match existing standard-beam construction.