Steel scaffolding grades define the yield strength, ductility and material standard of scaffold tubes, frames, props and fittings. The grade number refers to minimum yield strength (MPa)
Primary Steel Grades for Steel Scaffolding
Outer diameter: 48.3 mm
Wall thickness: 3.2 mm or 4.0 mm
Finish: black, painted, or hot-dip galvanized
Steel Grades:
- Chinese GB Standard:Q235,Q355
- European EN Standard:S235,S275,S355
- US ASTM Standard:ASTM A36,ASTM A500
- Japanese JIS Standard:STK400,STK500
S235 Vs S275 vs S355 Grades
S235, S275 and S355 are British and European standard scaffolding grades.
S235: Default grade for conventional scaffolding.
S275: Middle strength, seldom used for scaffold tubes.
S355: High strength for heavy-duty temporary support systems.
S235 Steel grade
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| Element | C | Si | P | S | N |
| Req, % | ≤0.20 | ≤0.30 | ≤0.05 | ≤0.05 | ≤0.009 |
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| Strengths |
Tensile Strength (Rm) (N/mm²) |
Yield Strength (ReH) (N/mm²) |
Elongation Lo =5.65 √So (%) |
| Required |
≥340 <480 |
≥235 | ≥24 |
Note: Refer to BS1139 Standard
S275 Steel Grade
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| Element | C | Mn | P | S | N |
| Req, % | ≤0.20 | ≤1.5 | ≤0.035 | ≤0.035 | ≤0.009 |
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| Strengths |
Tensile Strength (Rm) (N/mm²) |
Yield Strength (Rp0.2) (N/mm²) |
Elongation Lo =5.65 √So (%) |
| Required | 410-560 | ≥275 | ≥20 |
Note: Refer to EN10219 Standard
S355 Steel Grade
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| Element | C | Si | Mn | P | N |
| Req, % | ≤0.22 | ≤0.55 | ≤1.6 | ≤0.035 | ≤0.009 |
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| Strengths |
Tensile Strength (Rm) (N/mm²) |
Yield Strength (ReH) (N/mm²) |
Elongation Lo =5.65 √So (%) |
| Required | 470-630 | ≥355 | ≥20 |
Note: Refer to EN10219 Standard
When to choose which
- S235: Standard access scaffolds, tube-and-coupler, general construction. Usually the correct and most economical choice.
- S275: Rarely specified for scaffold tubes. It sits between S235 and S355 but rarely offers enough practical advantage to justify separate stock.
- S355: Heavy-duty system scaffolds, shoring, industrial/bridge scaffolds, high leg loads, long spans-where the higher yield strength is actually utilized.
Approximate equivalents: S235 ≈ Q235B / STK400 / A36; S275 ≈ Q275B; S355 ≈ Q345B / STK500
What this means in a scaffolding system
- Standards / verticals: Higher grade can increase axial capacity, but buckling and connection eccentricity often control. S355 is common in high-capacity proprietary systems.
- Ledgers / transoms: S355 helps where bending or yield controls, especially short spans and heavy loads.
- Braces: Grade helps in tension and stocky compression, but slender buckling is mainly geometry-dependent.
- Couplers / wedges / rosettes: These often govern. They are usually tested to EN 74 or the manufacturer's system standard, not simply specified as S235/S275/S355.
- Base jacks / screw jacks: Often forged or higher-grade components; thread and nut design matter more than tube grade.
- Deflection: Same E for all three. If sag or serviceability controls, use bigger section, shorter spans, or more supports-not a higher grade.
ASTM A36 and ASTM A 500 Grade
ASTM A36 and ASTM A 500 are the USA standard scaffold material grades, but they are different product forms:
ASTM A36: in base plates, couplers, frames, and other non-tube components.
ASTM A500: the primary steel for scaffold tubes, frames, posts
ASMT A 36 Steel Grade
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| Element | Carbon | Manganese | Phosphorus | Sulfur | Silicon |
| Req, % | ≤0.26 | – | ≤0.04 | ≤0.05 | ≤0.04 |
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| Strengths |
Tensile strength, min, psi[MPa] |
Yield point, min, psi[MPa] |
Elongation in 2 in. [50 mm], min,% |
| Required |
58-80 [400-550] |
36 [250] | 21 |
ASTM A 500 Steel Grades
ASTM A500 standard has steel grade A, grade B, Grade C, and Grade D.Grade B and Grade C are primarily selected for scaffolding materials.
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| Chemicals | Grade A, B, D | Grade C |
| Carbon, max | 0.30 | 0.27 |
| Manganese, max | 1.40 | 1.40 |
| Phosphorus, max | 0.045 | 0.045 |
| Sulfur, max | 0.045 | 0.045 |
| Copper, min | 0.18 | 0.18 |
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| Mechanical Property | Grade A | Grade B | Grade C | Grade D |
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Tensile strength, min, psi[MPa] |
45000 [310] | 58000 [400] | 62000 [425] | 58000 [400] |
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Yield strength, min, psi[MPa] |
33000 [230] | 42000 [290] | 46000 [315] | 36000 [250] |
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Elongation in 2 in. [50 mm], min,% |
25 | 23 | 21 | 23 |
Youfa Steel Pipe Group supplied scaffolding products for the Kenya Arena in 2024, with a total supply of 2300 tons. The supplied product is ringlock scaffolding, a modular steel structure system normally fabricated from S235 mild steel.
Ringlock scaffolding is a versatile, heavy-duty modular scaffolding solution. Its core design features circular rosette connectors that allow ledger braces and standards to be locked securely at multiple angles, delivering outstanding structural stability, high load-bearing capacity and fast assembly and disassembly.
This scaffolding system is used for temporary working platforms, formwork support, maintenance access and facade construction during the venue's building works. The robust steel components can withstand heavy construction loads and adapt flexibly to the complex curved architectural contours of the arena. The hot-dip galvanized surface treatment provides excellent anti-corrosion performance, which is essential to resist humidity and tropical weather conditions in Kenya.
Compared with traditional scaffolding types, ringlock scaffolding has fewer loose small fittings, greatly reducing the risk of lost parts and improving construction site safety. It can be reused multiple times for different projects, bringing good cost efficiency for large-scale public building construction.
