S275 vs S355 Structural Steel: Which Grade Should You Use?
S275 vs S355 compared: yield and tensile strength, JR/J0/J2 toughness subgrades, weldability, cost and when engineers specify each grade for Saudi projects.
Saudi Steel Work Editorial Team · · 3 min read
Short answer: S355 has a minimum yield strength of 355 MPa versus 275 MPa for S275 (for thicknesses up to 16 mm), about 29% higher. S355 often allows lighter sections and is now the default for many structures; S275 remains common for lightly loaded or stiffness-governed members. The structural engineer decides.
S275 and S355 are the two most common structural steel grades under EN 10025-2, widely used on Saudi projects designed to European or British practice. The number is the minimum yield strength in megapascals for the thinnest thickness range.
Key properties
| Property | S275 | S355 |
|---|---|---|
| Min. yield strength (t ≤ 16 mm) | 275 MPa | 355 MPa |
| Tensile strength (3 ≤ t ≤ 100 mm) | 410–560 MPa | 470–630 MPa |
| Typical uses | Light structures, secondary steel | Main frames, heavy structures |
Yield strength reduces slightly as thickness increases, according to the standard's thickness bands.
Toughness subgrades
Both grades come with suffixes:
- JR — 27 J at +20 °C
- J0 — 27 J at 0 °C
- J2 — 27 J at −20 °C
- K2 — 40 J at −20 °C (S355)
Saudi Arabia's climate rarely gets cold, but thicker sections and fatigue-loaded or dynamically loaded members may still require J0 or J2 under the design standard. See Charpy impact testing.
Why S355 is increasingly the default
- Higher strength can reduce section sizes and tonnage
- Lighter members reduce transport and erection effort
- Price difference between S275 and S355 is often modest relative to tonnage saved
When S275 still makes sense
- Members governed by stiffness or deflection rather than strength, where higher strength gives little benefit
- Secondary steel, stairs, handrails and miscellaneous metalwork
- Where availability of a specific section in S355 is limited
Equivalents
| EN grade | Approximate ASTM comparison |
|---|---|
| S275 | ASTM A36 (250 MPa yield) |
| S355 | ASTM A572 Grade 50 / A992 (345 MPa yield) |
These are not exact equivalents. See ASTM A36 vs A572 Grade 50.
Never substitute without approval
Supplying S275 where S355 was designed is a serious non-conformance. Supplying S355 where S275 was specified is usually acceptable structurally but should still be agreed. Certificates must confirm the delivered grade (mill test certificates).
Browse structural steel sections and steel plates, available on enquiry in both grades.