Scaffolding steel pipe is most often specified to EN 39 or BS 1139 in international projects. This guide compares the two standards on size, wall thickness and coupler compatibility, with selection guidance for export scaffolding orders.
Scaffolding steel pipe is one of the most standardized products in construction, with two British/European standards dominating global procurement: BS 1139 (now largely superseded by EN 12811 in the EU, but still the dominant reference in the Middle East, Africa and parts of Asia) and EN 39 (the European specification for loose tube used with couplers). For export scaffolding orders, the choice between EN 39 and BS 1139 affects the tube dimensions, the wall thickness, the coupler compatibility, and ultimately whether the system can be used on the customer's site.
What EN 39 Specifies
EN 39 specifies loose steel tube for use with EN 74 couplers, with outside diameter of 48.3 mm (1.5 inch nominal) and wall thickness of 3.2 mm or 4.0 mm. The steel grade is typically S235 or S275, with minimum yield strength of 235 MPa or 275 MPa. The tube is supplied in random lengths of 6 m or cut to length, with a hot-dip galvanized finish per EN 1461 being the standard for outdoor scaffolding. EN 39 tube is compatible with the full range of EN 74 right-angle couplers, swivel couplers and sleeve couplers used in European scaffolding systems.
What BS 1139 Specifies
BS 1139 Part 1 specifies scaffolding tube in the same 48.3 mm OD, with two traditional wall thicknesses: 4.0 mm (Class A) for heavy-duty scaffolding, and 3.2 mm (Class B) for general purpose. The steel grade and the hot-dip galvanized finish per BS 729 are equivalent to EN 39. BS 1139 tube is compatible with BS couplers (which are dimensionally the same as EN 74 couplers), so an EN 39 tube and BS 1139 tube are physically interchangeable in most scaffolding systems.
Choosing the Right Standard for Export Orders
For export to the EU, EN 39 is the required reference and the system should be referenced in the RFQ. For export to the UK, Middle East, Africa and Southeast Asia, BS 1139 is still widely accepted and often the expected reference. For global projects that may be assembled on different sites, dual certification (EN 39 + BS 1139) is a common practice. In all cases, the actual tube dimensions and wall thickness are the same, so the choice is primarily about which mill certificate the buyer wants to see in the file.
Wall Thickness, Coupler Fit and Field Issues
The most common field issue with scaffolding tube is the wall thickness not matching the couplers. EN 74 and BS 1139 couplers are designed for 3.2 mm or 4.0 mm wall; if the mill supplies 2.5 mm or 2.8 mm tube (which is cheaper but not standard), the couplers will not grip correctly and the scaffold will not meet code. Always confirm the wall thickness on the test certificate, and require a sample coupler fit test on the first batch of any new supplier.
What to Specify on the Scaffolding Tube RFQ
State the standard (EN 39 or BS 1139 Part 1, or both), the OD (48.3 mm), the wall thickness (3.2 mm or 4.0 mm), the steel grade (S235 / S275 or equivalent), the length (6 m or cut to length), and the finish (hot-dip galvanized per EN 1461 / BS 729). For heavy-duty scaffolding or high-rise applications, default to 4.0 mm wall. For general purpose scaffolding, 3.2 mm wall is acceptable and saves weight. Always require the mill test certificate and confirm the coupler compatibility before bulk shipment.
Related Resources from Baobin Steel
- Carbon steel pipe catalog – scaffolding and structural tube
- Mild steel overview – grades and standards
- Request a quote – send your scaffold spec for tube pricing