A 1.25-Ton Steel Stair: HM294 Stringers and 6 mm Treads

English Version

Title: Steel Stair, 1,251 kg Total: HM294×200 Stringers, 6 mm Treads, Bolted M22 Joints

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Overview

An industrial steel stair is a small structure with a big job: it carries people up 5 m, several times a day, for twenty years, with handrails that have to stop a fall. This project's stair is a straight flight with a top platform, built from hot-rolled H-section stringers, 6 mm tread plate, and bolted connections — the standard workshop access stair.

The material list gives the whole picture: 1,251.1 kg of steel, one flight, one drawing number.

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Material Data (from Drawing Material List)

 

Mark	Section / Description	Length (mm)	Qty	Weight (kg)	Material
3EGH20	HM294×200×8×12	220	1	12.3	Q355B
3EGH21	HM294×200×8×12	4,244	2	473.4	Q355B
3EGH28	HM294×200×8×12	511	1	28.5	Q355B
3EGH29	HM294×200×8×12	511	1	28.5	Q355B
3EGH30	HM294×200×8×12	220	1	12.3	Q355B
3EGL19	L60×5 angle	1,310	2	12.0	Q355B
3EGP10	PL12×96	270	8	19.5	Q355B
3EGP52	PL8×569 (platform)	1,800	1	66.5	Q235B 8 mm
3EGP53	PL8×575 (platform)	1,800	1	67.2	Q235B 8 mm
3EGP55	PL6×1800	184	1	16.2	Q235B 6 mm
3EGP57	PL6×1800 (treads)	436	12	459.1	Q235B 6 mm
3EGP58	PL6×146	263	24	43.2	Q235B
3EGP59	PL6×126	227	2	2.7	Q235B
3EGP63	PL12×96	270	4	9.8	Q355B
—	M22 bolts, grade 10.9	55	12	—	10.9
Total				1,251.1

Drawing no. 3-A4-02GT-1. Stair rises from elevation -0.10 m to about +4.90 m, with a top platform.

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What Each Part Does

HM294×200×8×12 stringers (2 @ 4,244 mm): the two main inclined beams that carry the whole stair. 294 mm depth gives stiffness under footfall and a safe deflection limit.

PL6×1800 treads (12 pcs @ 436 mm): 6 mm plate treads, welded or bolted between stringers; 436 mm going sits in the comfortable step range.

PL8×569/575 platform plates: the landing at the top, 8 mm plate for heavier foot traffic.

PL12×96 members (12 pcs): handrail posts and stiffeners — 12 mm plate, the part that takes a body falling against the rail.

L60×5 angles: handrail and toe-board framing.

M22 grade 10.9 bolts (12 sets): the stringer-to-support connection; bolted so the stair can be installed after the frame is up.

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Advantages

Fast to fabricate and install — a 1.25 t stair is shop-welded and site-bolted in a day; the frame can be finished before the stair arrives.

Hot-rolled stringers are straight and strong — HM294×200×8×12 needs no welded build-up; the mill section carries the stair load with margin.

Light for its height — 1.25 t for a 5 m stair means a small crane or a forklift can set it.

Standard sections, easy to repair — damaged treads or posts are swapped with plate pieces, no custom castings.

Bolted connection allows adjustment — M22 10.9 bolts let the stair be aligned and re-tightened on site.

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Disadvantages / Limitations

6 mm treads wear — plate treads in a busy plant show edge wear and can become slippery; checkered plate or nosings are often added.

No closed stringer — an open H-section stringer leaves the tread ends visible; dust and water collect on the flanges.

Handrail loads govern the posts — PL12×96 posts are sized by the code handrail load, not by the stair weight; a lighter post is a safety issue, not a saving.

Bolted joints need inspection — M22 10.9 bolts must be torque-checked; a loose stringer connection lets the stair move under footfall.

Not for extreme heights — above about 6–8 m, a straight flight becomes too long; a switchback or a lift is the better answer.

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Typical Use Cases

Workshop access stairs — operator access to mezzanines, crane cabs, and equipment platforms (this drawing, 5 m rise).

Plant room stairs — access to rooftop plant, boiler rooms, and pump rooms.

Maintenance stairs in warehouses — short flights to racking mezzanines and conveyor levels.

Temporary erection stairs — bolted stairs installed after the frame is up and removed after commissioning.

Outdoor access stairs — weather-protected stairs to loading docks and service yards.

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Fabrication and Installation Notes

Stringers: HM294×200×8×12, Q355B — check the mill certificate; keep the two stringers parallel within tolerance before welding treads.

Treads: PL6×1800 cut to 436 mm going; weld or bolt per drawing; add anti-slip nosing on heavily used stairs.

Platform: PL8×569 / PL8×575 plates at the top landing; check level before fixing.

Handrail: PL12×96 posts and L60×5 rails; post spacing and height per the safety code (typically 1,050–1,100 mm).

Bolts: M22 grade 10.9, 12 sets; torque per the bolt standard and re-check after the first week of use.

Erection: set the stair after the frame and platform are complete; check the top landing level against the drawing elevation (+4.90 m).

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Bottom Line

A 1,251 kg steel stair is the cheapest safe way up 5 m: two HM294×200×8×12 stringers, twelve 6 mm treads, an 8 mm landing, and M22 10.9 bolts. It is fast to build, easy to repair, and light enough for a small crane. The parts that matter are the ones people touch — treads and handrail. Get those right, and the stair lasts as long as the building.

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