Plate stringers will either utilise standard flat bar steel sections or can be profile cut any size or shape from plate material for a very custom solution as required. Typically this stringer type allows for a space efficient design with stringers sourced/cut from 12mm, 16mm, 20mm, 25mm or 32mm mild steel or stainless steel plate, subject to engineer or design requirements.
Also a type of plate stringer, this design is also cut from either 16mm, 20mm, 25mm or 32mm flat mild steel or stainless steel plate, subject to engineers approval and the requirements of the design. An architectural statement intent.
Double plate or H stringer
Another variation of the plate or profile cut stringer but with 2 plates to create a continuous pocket for grouting glass. Plate thickness would be determined by the project engineer.
A very common and robust stringer design, the PFC (parallel flanged channel) can either be left exposed, or sometimes for strength it will be plated to form a narrow hollow section.
A robust though sometimes bulky alternative, the box stringer (sometimes called RHS) is a common detail on steel stairs. Available in either square or rectangular shapes, the width of the section will often impact the final width of the stairs, so special care should be taken with detailing if space is at a premium.
*Note – all external corners of such sections have a radius.