What Is BS 1387?
BS 1387 is the British standard for screwed and socketed steel tubes and tubulars, and for plain end steel tubes suitable for welding or for screwing to pipe threads. Originally issued in 1985, the standard defined light, medium and heavy classes of tube with specified dimensions, threading and galvanizing requirements.
For new projects the standard has been superseded. General purpose tubes are now specified to EN 10255, and tubes for scaffolding are specified to EN 39, which defines the 48.3 mm outside diameter tube with 3.2 mm or 4.0 mm wall thickness. BS 1387 designations are still widely used in trade and in legacy specifications, so it is important to map the old designation to the current European standard when procuring.
Material and Manufacturing
Scaffolding tubes are made from low-carbon steel, commonly a grade equivalent to S235, which combines good strength, ductility and weldability. The tube is formed by high-frequency welding of steel strip, followed by sizing and straightening. The tube can then be hot-dip galvanized to protect it against corrosion in outdoor and humid service.
For scaffolding duty the typical tube is 48.3 mm outside diameter with a 4.0 mm wall thickness to EN 39, or the lighter 3.2 mm wall where the design load allows. Plain end tubes can be welded on site; threaded tubes are used with couplers and fittings.
Hot-Dip Galvanizing
Hot-dip galvanizing immerses the fabricated tube in molten zinc, forming a dense, metallurgically bonded zinc coating on the outer and inner surfaces. A zinc coating thickness of 65 microns or more provides long-term corrosion protection in atmospheric, humid and mildly aggressive environments, and is the standard class for scaffolding tubes that will be stored outdoors.
Galvanized tubes resist rusting far longer than black tubes and are the default choice for scaffolding, water supply, HVAC and fire sprinkler piping. The zinc layer also gives a clean, recognizable finish that simplifies site inspection.
Dimensions and Threading
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| Parameter | Value |
|---|---|
| Outside Diameter | 48.3 mm for scaffolding tube |
| Wall Thickness | 3.2 mm or 4.0 mm |
| Standard Length | 5.8 m, with plus or minus 3 mm tolerance |
| Thread Type | BSP 55 degree taper threads, or custom NPT |
| Thread Precision | 6G class for custom NPT |
| End Protection | Plastic end caps to protect the zinc layer |
Threaded tubes are furnished with taper threads that seal by thread interference, which suits screwed and socketed joints for water and gas service. Custom NPT external threads can be machined to 6G precision with a 55 degree thread angle for compatibility with imperial fittings and reliable sealing.
Precision-Cut Lengths and Marking
Pipes can be produced to customer-specified lengths, with 5.8 m as the standard scaffold length. The tight length tolerance minimizes on-site cutting waste and speeds erection. Each tube can be laser-marked with the specification, batch number and compliance standard, giving full traceability for project management and quality audits. Plastic end caps protect the zinc coating against abrasion and contamination during transport and storage.
Applications
Galvanized BS 1387 type tubes are used for access scaffolding in construction and maintenance, fire sprinkler systems, water supply and drainage, HVAC pipework, handrails and temporary structures. The galvanized coating makes them particularly suitable for humid, coastal, acidic or alkaline environments where bare steel would corrode quickly.
Handling and Storage
Stack tubes on level timber dunnage to keep them clear of the ground and allow drainage. Keep the plastic end caps fitted until the tube is used, and avoid dragging tubes across hard surfaces, which can scrape the zinc and create corrosion initiation points. Damaged coatings can be repaired with zinc-rich paint; consult the coating specification for the approved repair method.
Common Misconceptions
A common error is assuming BS 1387 is still the governing standard for new scaffolding; EN 39 is the current scaffolding tube standard, with EN 10255 for general screwed and socketed tubes. Another misconception is that thicker zinc always means a stronger tube; the load capacity depends on wall thickness and steel grade, not the coating. A third error is welding galvanized tubes without removing the zinc from the weld area; zinc fumes are hazardous and porosity can form, so weld preparation must follow the safety rules.
FAQ
Is BS 1387 still valid for scaffolding tubes?
BS 1387 was withdrawn and replaced. For new scaffolding use EN 39, which specifies the 48.3 mm tube, and for general threaded tubes use EN 10255. Many suppliers still mark legacy BS 1387 sizes for convenience.
What is the standard size of a scaffolding tube?
The standard scaffolding tube is 48.3 mm outside diameter with a 4.0 mm wall thickness, supplied in lengths up to 6.5 m with 5.8 m being common.
Why are scaffolding tubes galvanized?
Galvanizing protects the steel against corrosion in outdoor service, extends service life, reduces maintenance and keeps the tube surface clean and safe to handle.
Can galvanized tubes be welded?
Yes, but the zinc must be removed from the weld zone first and the work done with proper ventilation because zinc fumes are toxic. The galvanized layer is then repaired after welding.
What is the difference between BSP and NPT threads?
BSP threads have a 55 degree profile and are common in British and European systems; NPT threads have a 60 degree profile and are common in North America. They are not interchangeable.
What zinc thickness is recommended for scaffolding tubes?
A hot-dip zinc coating of 65 microns or more is the standard for scaffolding tubes, providing reliable protection in atmospheric and humid conditions.