Stair Base Connections: The Hidden Joint That Holds Every Steel Stair Up

Stair base connections anchor steel stair stringers to concrete foundations. Below is MJ-1 embedded plate from an actual steel stair foundation detail.

Basic Specs

Structure Details

The stair base connection consists of:

• Embedded plate MJ-1: 400×240×10 mm steel plate on foundation top
• Anchor rods: 2×Φ12 hooked rods embedded in concrete
• C25 foundation: 1000×500 mm concrete footing
• Rebar: double-layer Φ12@150 mesh
• Concrete boot: C10 concrete 100 mm thick, 100 mm tall above floor

Advantages

1. Simple and reliable — embedded plate bolted/welded to stair stringer
2. Precise positioning — plate set before concrete pour, correct alignment
3. Load distribution — 10 mm thick plate spreads stair load to concrete
4. Concrete boot protection — C10 boot protects steel base from moisture
5. Standard detail — works for [-30a, HN300 and □250 stair types

Disadvantages / Limitations

1. Position must be exact — wrong embed position cannot be fixed after pour
2. Needs formwork cooperation — plate fixed before concrete pour
3. Weld inspection needed — stringer-to-plate weld must be checked
4. Corrosion at base — steel plate near floor level rusts if boot cracks
5. Not adjustable — bolted connections allow adjustment, welded don't

Typical Applications

1. Industrial factory stairs — access to mezzanine and platforms
2. Warehouse steel stairs — access to storage mezzanine
3. Outdoor steel stairs — exterior fire escape stairs
4. Equipment platform stairs — access to machinery platforms
5. Roof access ladders — roof maintenance access

Fabrication Notes

• MJ-1 plate shop-welded to anchor rods, positioned before concrete pour
• Foundation poured with C25 concrete, rebar Φ12@150 both ways
• Stair stringer ([-30a) welded or bolted to MJ-1 plate
• C10 concrete boot poured after stair installed, 100 mm tall

MJ-1 stair base connection — 400×240×10 mm embedded plate, 2×Φ12 anchor rods, C25 concrete foundation 1000×500 mm, Q235B, anchoring steel stairs to concrete.

**WhatsApp**: +86‑13889862778, +86‑18242444407
**Email**: eddie@zdsteels.com, wells@zdsteels.com