Structural steel staircases, landings, and platforms are among the most common welded assemblies in commercial and industrial construction. Despite their ubiquity, weld procedure requirements for stair fabrication are frequently misunderstood — especially in smaller shops where a staircase looks too simple to warrant formal WPS documentation.
AWS D1.1:2025 governs structural steel staircases, landings, and mezzanine platforms when they are part of a structure subject to the code. The fabricator's quality control program must include applicable WPS documents, current welder performance qualification records (WPQs), and a documented CWI inspection process.
Applicable Code and Jurisdiction
AWS D1.1:2025 applies to structural steel assemblies — including stairs, landings, catwalks, and platforms — when contract documents reference it. The International Building Code mandates AWS D1.1 as the standard for structural steel welding, and AISC certification programs require an AWS D1.1-compliant welding quality control plan.
The engineer of record's project specifications confirm the applicable edition. AWS D1.1:2025 is the current edition; projects that began before the 2025 ANSI approval may still reference the 2020 edition. Rule library based on AWS D1.1:2025; verify against your governing edition.
OSHA 1910.23 and 1926.502 govern stairway geometry — riser height, tread depth, handrail height — but they do not specify weld quality. Weld quality requirements flow entirely from AWS D1.1 and the engineering specification.
Common Joint Types in Stair Fabrication
A typical structural steel staircase involves the following weld connections:
Stringer-to-tread connections. Treads (checkered plate, bar grating, or fabricated pan) attach to the stringer web or flange with fillet welds on each side. Prequalified fillet weld joint details per Clause 5 apply when the geometry is a T-joint or lap joint within the prequalified limits.
Stringer-to-landing connections. The top and bottom ends of each stringer frame into landing beams or header beams, typically through shear tab or clip-angle connections. These are fillet weld joints in the flat or horizontal position when the sub-assembly can be positioned on a worktable.
Landing frame connections. Landing beams frame into columns or floor framing with fillet welds on plate connections. The joint geometry follows standard T-joint or lap-joint prequalified fillet configurations in Clause 5, Figure 5.1.
Handrail post base plates. Steel pipe or tube posts are welded to base plates with fillet welds all around. If the base plate is itself welded to the stringer — rather than bolted — that attachment weld must also be covered by the applicable WPS.
Diagonal kickers and struts. Industrial stairs frequently use angle or WT struts to resist horizontal forces. These are typically fillet-welded to the stringer or frame with single-sided or double-sided fillet welds at T-joints or lap joints.
Minimum Fillet Weld Size: Table 7.7
The most frequently cited AWS D1.1:2025 requirement for stair fabrication is minimum fillet weld size from Table 7.7. For low-hydrogen processes — SMAW E7018, FCAW-G E71T-1/T-9, GMAW ER70S-6 — the minimum is based on the thinner of the two parts joined:
| Thinner part joined | Minimum fillet weld size |
|---|---|
| ≤ 1/4 in [6 mm] | 1/8 in [3 mm] |
| > 1/4 in to 1/2 in [6 to 12 mm] | 3/16 in [5 mm] |
| > 1/2 in to 3/4 in [12 to 20 mm] | 1/4 in [6 mm] |
| > 3/4 in [20 mm] | 5/16 in [8 mm] |
Light tread plates (3/16 in or 1/4 in checkered plate) are typically the thinner member, so they control the minimum weld size — 1/8 in or 3/16 in. The drawing callout specifies the actual required weld size, which must be at least the Table 7.7 minimum. The structural engineer may call out a larger weld for load reasons; that is a design decision separate from the code minimum.
For non-low-hydrogen processes — bare GMAW short-circuit transfer, FCAW-S E71T-11 — the thicker of the two members controls the minimum, unless preheat requirements are satisfied per the applicable code provision. Most production stair shops use low-hydrogen consumables and avoid this distinction.
See minimum fillet weld size under AWS D1.1:2025 Table 7.7 for the full table discussion including the thicker-part exception.
Process and Filler Metal Selection
SMAW with E7018: The traditional choice for stair fabrication — portable, versatile, and suitable for all positions. E7018-H4 is preferred when connecting members with wall or flange thicknesses above about 1 in. E7018 low-hydrogen electrodes must be stored in a rod oven or opened from hermetically sealed packaging; exposure time limits apply.
FCAW-G with E71T-1 or E71T-9: Higher deposition rate than SMAW, suited for production stair shops. E71T-9 indicates tested impact properties, required when the engineering specification calls out CVN toughness for weld metal. Confirm the shielding gas mixture (C25 or 100% CO₂) matches the WPS, as the gas mixture is an essential variable.
GMAW with ER70S-6: Clean, low-spatter welds preferred in exposed architectural stair fabrication. Spray or pulse transfer is typically specified for structural GMAW fillet welds; the WPS must document the transfer mode, which is an essential variable under AWS D1.1:2025.
A36 steel is a Group I prequalified base metal, and A572 Grade 50 is a Group II prequalified base metal under Table 5.6 in AWS D1.1:2025. A500 Grade B (round or rectangular HSS for post columns and stringer chords) is also listed in Table 5.6. Before relying on a prequalified WPS, confirm that every base metal in the assembly appears in Table 5.6 and that the applicable group is covered by the WPS.