Steel scaffolding is the most commonly used scaffold type in construction. Steel grades are an essential factor for steel scaffolding that impacts the construction loading and bearing. You can find the significant scaffold grades here and check their differences to help you choose the right grades for your steel scaffolding.
Primary Steel Grades for Steel Scaffolding
There are seven popular steel grades according to international scaffolding standards.
- S235 grade
- S355 grade
- S275 grade
- STK 400 grade
- STK500 grade
- ASTM A36 grade
- ASTM A500 grade
- S275 grade
S235, S275 and S355 Grades
s235, S275 and s355 are British and European standard scaffolding grades.
S235 Steel grade
It is the most common steel grade for steel scaffolding materials, significant with a minimum yield strength of 235 N/mm².
Chemical Composition Requirement of S235 Grade
| Element | C | Si | P | S | N |
| Req, % | ≤0.20 | ≤0.30 | ≤0.05 | ≤0.05 | ≤0.009 |
Mechanical Properties Requirement of S235 Steel Grade
| 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
It is a higher grade of material for scaffolding with a minimum yield of 275 N/mm².
Chemical Composition Requirement of S275 Grade
| Element | C | Mn | P | S | N |
| Req, % | ≤0.20 | ≤1.5 | ≤0.035 | ≤0.035 | ≤0.009 |
Mechanical Properties Requirement of S275 Steel Grade
| 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
S355 is the highest grade for typical scaffolding steel materials with a minimum yield strength of 355 N/mm²
Chemical Composition Requirement of S355 Grade
| Element | C | Si | Mn | P | S | N |
| Req, % | ≤0.22 | ≤0.55 | ≤1.6 | ≤0.035 | ≤0.035 | ≤0.009 |
Mechanical Properties Requirement of S355 Steel Grade
| 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
High yield and tensile strength steel raw material can bring a higher load capacity and weight bearing in construction (suppose: same diameters, thickness and sizes scaffold products). That means if you want a higher load capacity, S355 is better than S275, and S275 is better than S235.
STK 400 and STK 500 Steel Grades
STK 400 and STK 500 are Japanese and Korean standard scaffolding material grades.
STK 400 Steel Grade
STK 400 steel grade has a minimum yield strength of 235 Mpa in the Japanese scaffolding standard.
Chemical Composition Requirement of STK 400 Steel Grade
| Element | C | Si | Mn | P | S |
| Req, % | ≤0.25 | – | – | ≤0.040 | ≤0.009 |
Mechanical Properties Requirement of STK400 Steel Grade
| Strengths | Tensile Strength (Rm) (MPa) | Yield Strength (Rp0.2) (MPa) | Elongation after fracture(A) Lo =50mm (%) |
| Required | ≥400 | ≥235 | ≥16 |
STK 500 Steel Grade
STK 500 grade steel scaffolding material has a minimum of 355 Mpa in the Japanese standard.
Chemical Composition Requirement for STK 500 Steel Grade
| Element | C | Si | Mn | P | S |
| Req, % | ≤0.24 | ≤0.35 | 0.30-1.30 | ≤0.040 | ≤0.040 |
Mechanical Properties Requirement of STK500 Steel Grade
| Strengths | Tensile Strength (Rm) (MPa) | Yield Strength (Rp0.2) (MPa) | Elongation after fracture(A) Lo =50mm (%) |
| Required | ≥500 | ≥355 | ≥8 |
Refer to JIS 3444 Standards
In the Japanese standard, STK 500 has a higher mechanical property and provides a higher load for scaffolding and construction.
ASTM A36 and ASTM A 500 Grade
ASTM A36 and ASTM A 500 are the USA standard scaffold material grades.
ASMT A 36 Steel Grade Requirement for Scaffolding Material
ASTM A36 steel grade has a minimum yield point requirement of 250 Mpa.
Chemical Composition of ASTM A36 Steel Grade
| Element | Carbon | Manganese | Phosphorus | Sulfur | Silicon |
| Req, % | ≤0.26 | – | ≤0.04 | ≤0.05 | ≤0.04 |
Mechanical Properties of ASTM A36 Steel Grade
| Strengths | Tensile strength, min, psi[MPa] | Yield point, min, psi[MPa] | Elongation in 2 in. [50 mm], |
| Required | 58-80 [400-550] | 36 [250] | 21 |
ASTM A 500 Steel Grades for Scaffolding Material
ASTM A500 standard has steel grade A, grade B, Grade C, and Grade D.
- Grade A has a minimum yield requirement of 230 Mpa.
- Grade B has a minimum yield requirement of 290 Mpa.
- Grade C has a minimum yield requirement of 315 Mpa.
- Grade D has a minimum yield requirement of 250 Mpa.
Grade B and Grade C are primarily selected for scaffolding materials.
Chemical Composition of ASTM A500 Steel Grade
| 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 |
Mechanical Properties of ASTM A500 Steel Grade
| Mechanical Property | Grade A | Grade B | Grade C | Grade D | |
| Tensile strength, min, psi[MPa] | 45000 [310] | 58000 [400] | 62000 [425] | 58000 [400] | |
| Yield strength, min, psi[MPa] | 33000 [230] | 42000 [290] | 46000 [315] | 36000 [250] | |
| Elongation in 2 in.[50 mm], min,% | 25 | 23 | 21 | 23 | |
Grade C has higher mechanical properties and strengths than Grades A, B, and D in the ASTM A500 standard. That means scaffold material of ASTM A5o0 grade C can take more weight in construction bearing.
Refer to ASTM A36 and ASTM A 500 Standards.
How to Select Steel Grade for Your Scaffolding Materials?
Consider the Load Capacity Requirement of Your Construction
- Regular load steel scaffolding material: Choose S235, STK 400, ASTM A 36, or ASTM A 500 grade B.
- Higher load steel scaffolding material: Choose S355, STK 500, ASTM A 500 grade C
Balance Cost and Load Capacity in Steel Grade Selection
The higher grade cost of S355, STK 500, and ASTM Grade C is usually higher than the regular steel grade of S235, STK 400, ASTM A36 or ASTM A 500 Grade B.
You can choose high grades for significant scaffold parts of scaffolding standards, ledgers, and braces to balance cost and load capacity. Other scaffolding elements can choose regular steel grade.
Thinner thickness scaffolding needs to choose higher grades.
For thin scaffold material, you must choose a high grade for your steel scaffolding to balance the lower thickness.
Test Report of Steel Scaffolding Material Grades Download
- Test Report of S355 Grade Scaffold according to EN 10219
- Test Report of S235 Grade Scaffold According to BS1139
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