Stair Tread Load Tables

Design basis

• Material: carbon steel, ASTM A1011, F_y = 36 ksi; also available in stainless 304/316 and aluminum 6061-T6.
• Pattern: welded 19-W-4 with 1-3/16" (30 mm) bearing bar centers, 4" cross bars, checker-plate or serrated top.
• Nosing: project-selected checker plate, abrasive or other detail; state dimensions, contrast and slip-performance requirements.
• Support: two end brackets / carrier plates, bolt or weld to stringers.
• Design loads: state the governing code, uniform and concentrated values, contact area, load combinations and deflection limit. OSHA, IBC and local requirements vary by use and jurisdiction.

Allowable concentrated midspan load — welded 19-W-4, 3/16" bar

Preliminary reference only: concentrated load is applied at mid-span over the stated contact area under the page assumptions. These values do not establish code compliance and do not verify carrier plates, welds, bolts or stringers. Confirm the complete tread and attachment for the governing project criteria.

Allowable uniform load — stair tread

Standard tread dimensions

FAQ — stair tread load tables

Does a 1" × 3/16" stair tread meet my project code?

Not enough information. Confirm the governing code, clear span, width, bearing-bar arrangement, carrier plates and connections, uniform and concentrated loads, footprint, load factors and deflection limit. Verify the complete tread and attachments.

What is the standard stair tread width (depth)?

Typical commercial depth is 9-7/8" (250 mm) or 11-1/8" (283 mm) measured nose-to-nose. Both depths use the same bearing bar, different number of bearing bars.

Do I need serrated or smooth bearing bars?

Use the project slip-risk assessment. Wet, oily or contaminated service may call for serrated bars, a tested nosing or another treatment, but no single surface is automatically compliant in every location.

Can treads be galvanized after fabrication?

Yes. Hot-dip galvanizing per ASTM A123 is applied after welding and drilling of carrier-plate holes. Nosing and carriers are galvanized as an assembly.

How is the maximum tread length determined?

It depends on bar size, tread depth, construction, transport and project loads. Submit the clear span and load cases; the quotation and approved drawing state the offered limit.