Straight steel stairs

What it is

A straight stair is a single flight running in one direction between two levels, with a landing at the top and, on longer rises, intermediate landings in line. It is the simplest and most economical steel stair and the usual access to platforms, mezzanines, equipment and roof areas in industrial buildings. Where there is no room for a long straight run, a switchback stair folds the same rise into a smaller footprint.

World Steel supplies straight stairs as complete kits – stringers, grating treads or plate treads, landing frames, stair rails and guardrails, base plates and all bolts – detailed to the actual floor-to-floor height on site.

Types and options

Design and compliance

Stair geometry depends on the destination and on whether the stair is a workplace access (machinery, plant, maintenance) or a stair in a building used by the public. The designer decides which rules apply; World Steel checks the geometry and loads on every stair it details.

• US workplaces (OSHA 1910.25): angle 30°–50°, riser ≤ 9.5 in, tread depth ≥ 9.5 in, width ≥ 22 in, headroom ≥ 80 in; stairs carry 5 × the anticipated live load and not less than a 1,000 lb concentrated load. Handrails 30–38 in above the tread leading edge; stair rail systems installed since 17 January 2017 need a top rail of at least 42 in.
• US buildings (IBC 2021): riser 4–7 in, tread ≥ 11 in, width ≥ 44 in (36 in where occupant load is below 50), headroom ≥ 80 in, handrails 34–38 in, guards ≥ 42 in. Rail loads per ASCE 7: 50 lb/ft and a 200 lb concentrated load.
• Australia (AS 1657): angle 20°–45°, riser 130–225 mm, going 215–355 mm, 2R + G 540–700 mm, headroom ≥ 2000 mm, rails 900–1100 mm. Public stairs to NCC 2022: riser 115–190 mm, going 250–355 mm, 2R + G 550–700 mm, handrails ≥ 865 mm.
• Europe (EN ISO 14122-3): angle 20°–45°, preferably 30°–38°; 600 mm ≤ g + 2h ≤ 660 mm; width ≥ 600 mm, preferably 800 mm; guard-rail ≥ 1100 mm with knee-rail and toe-plate. Stairs in buildings follow national regulations and EN 1991-1-1 loads.

Under AISC 303 stairs are "other steel" items (CSI 05 51 00 Metal Stairs) unless the contract says otherwise. In the EU, load-bearing stairs are CE-marked to EN 1090-1 under World Steel's EN 1090 certification.

Fabrication and finishing at World Steel

Stringers are CNC-cut and drilled so tread holes line up exactly; landing frames and rail posts are welded in jigs. Welding follows AWS D1.1, AS/NZS 1554.1 or EN 1090-2 / EN ISO 3834-2 procedures and is visually inspected, with NDT where the specification requires it. Stairs can be trial-assembled in the shop to check rise, going and rail continuity. Components are galvanized by qualified galvanizers to ASTM A123, AS/NZS 4680 or EN ISO 1461, or painted to the project system, and shipped as bolted kits to protect the finish.

Installation and specifying

Survey the actual floor-to-floor height before shop drawings are approved – a few millimetres difference changes every riser. On site, set the base plates, lift the stringer pair as one braced unit, bolt to the landing beam, then install treads and rails. Specify the floor-to-floor height, available run, width, code basis, tread type, rail type and finish, and send the platform model where possible – see PEB stairs, ladders and gratings.