What riser and going dimensions should I use for a steel staircase?

Building Regulations Approved Document K specifies: private stairs — riser 150-220mm, going 220-300mm, pitch max 42°. Utility stairs — riser 150-190mm, going 250-400mm, pitch max 38°. The 2R + G rule (twice the riser plus the going) should give 550-700mm. A typical commercial steel staircase uses 175mm riser and 250mm going.

What stringer section is typically used?

Parallel Flange Channels (PFC) are the most common stringer section for steel stairs as they provide a flat inner face for tread bracket welding. Typical sizes are 150x75 PFC for short flights up to 3m, 200x90 PFC for spans up to 5m. For heavier loading or longer spans, UBs can be used but require more fabrication for tread connections.

What tread material should I specify?

Durbar (checker plate) is the standard tread material for industrial and commercial steel stairs — typically 6mm thick. For public buildings, concrete-filled treads (using folded plate pans) are common. Open mesh treads (Weldlok/Webforge) are used where drainage or ventilation is needed. All treads must have a non-slip nosing per BS 8300.

How wide should a steel staircase be?

Building Regulations require minimum 800mm for private stairs, 1000mm for commercial/public stairs. Fire escape stairs must be 1050mm minimum (up to 250 people) or wider for larger populations per BS 5588. The clear width is measured between handrails, not between stringers. Allow 100mm extra width for handrail standoff from the wall.

Does a steel staircase need fire protection?

Protected escape stairs in commercial buildings require 30 or 60 minutes fire resistance. Steel stairs can be protected with intumescent paint (thin film for 30 min, thick film for 60 min), fire-rated boarding, or spray-applied protection. Concrete-filled treads provide inherent fire resistance. Building Control will specify the required fire rating.

TradeCalculator

Steel Staircase Calculator — Stringer, Treads & Landings

Calculate steel staircase components per BS 5395. Determines stringer section, tread brackets, landing beam, and estimated weight for fabrication.

Floor-to-Floor Height

Total height from finished floor to finished floor

Stair Width

Clear width between stringers

Riser Height

150-220mm private, 150-190mm utility

Going Depth

220-300mm private, 250-400mm utility

How We Calculate This

This calculator determines the components for a straight-flight steel staircase, following BS 5395 for dimensional requirements and standard fabrication practice.

Calculation method

Risers: Floor-to-floor height ÷ preferred riser height
Flight length: (Risers - 1) × going depth
Stringer length: √(flight length² + height²)
Stringer section: Selected from span and loading tables

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.