Class A vs Class B Couplers under BS EN 74-1:2022+A1:2025: What the Class Means and How to Prove It

An order that says “EN 74 Class B” is asking for something specific, and a supplier can answer it with a stamped letter or with documents. A stamped letter on its own does not prove the class. This guide sets out what Class A and Class B mean for each coupler type in the current edition, BS EN 74-1:2022+A1:2025, who decides which class a job needs, and what to ask for before you accept, or offer, a class.

What the class means, type by type

Clause 4.2.1 says that Classes A and B differ in the internal forces and moments the coupler can transmit and in their load-bearing and stiffness values. Table 8 gives the numbers. These are the headline rows for each of the four coupler types that BS EN 74-1:2022+A1:2025 covers:

Transcribed from Table 8 of BS EN 74-1:2022+A1:2025. For right-angle, swivel and parallel couplers, Table 8 also has a slipping row at Δ1 ≤ 7 mm and an indentation test; the full right-angle and swivel tables are in the double coupler and swivel coupler guides. The sleeve coupler has only the two rows shown here, slipping at 1–2 mm and the Class B bending moment; the sleeve coupler vs joint pin guide covers it. There is no separate parallel-coupler guide, so its headline values are the ones in this table.

Three points stand out from the table:

1. “Class B” is not one strength. In this edition a Class B swivel coupler has a failure-force requirement of 20,0 kN; a Class B right-angle coupler has 30,0 kN. A class letter means something only next to a coupler type and an edition.
2. For a right-angle coupler, Class B adds requirements, not only bigger numbers. The rotational and cruciform-bending requirements exist only in Classes B and BB, and Table 8 marks them as applying to screw couplers only. A test report for a Class B screw-type double coupler therefore has to cover tests that a Class A report does not.
3. AA and BB are right-angle classes only. The doubled letters allow two identical couplers to be positioned touching each other to increase slipping capacity, and Table 8 also sets a higher single-coupler failure force for them (AA 30,0 kN, BB 45,0 kN). The double coupler guide explains the pairing rule.

Who decides the class

Clause 6.2.1 of BS EN 74-1:2022+A1:2025 sends the reader to EN 12811-1 and EN 12812 for the values and safety coefficients to apply in use, which is design work. That is why we treat the class as a design and specification input: confirm it with the buyer and the person responsible for the scaffold design, and do not let a supplier change it on its own. Our job as a sourcing partner is to find couplers that meet the class on the order and to show the evidence for it.

Two consequences follow:

• Class letters are per type. One order can call for Class B double couplers and Class A swivels. Each coupler type needs its own line and its own class, written as a clause 8 designation such as EN 74-1 RA B C2 M for the doubles and EN 74-1 SW A C2 M for the swivels.
• Countries differ on assessment. The note to clause 12 says requirements for assessment vary between countries. If the coupler will be used in a country you have not supplied before, ask the buyer which assessment and which documents they accept before you quote.

What supports a class claim: assessment, manual and a matching mark

Clause 9 of BS EN 74-1:2022+A1:2025 requires every coupler to carry a mark that includes its class, impressed or embossed on the flap or body and legible after coating. The manufacturer applies that mark. Clause 12 requires the assessment to be carried out by a person or organisation different from the coupler’s designer, and clause 13 requires the product manual to name the assessor and include a copy of the assessment statement. So the evidence chain runs in this order:

1. The type-test assessment for this coupler type and this class, against a named edition.
2. The product manual, which names the assessor and carries the assessment statement.
3. The mark on the coupler, which has to match both.

A mark without the first two links is a claim, not evidence.

What to check in a Class B report. Make sure it covers the class you are buying, not only the coupler type. For a screw-type right-angle coupler under the current edition, Table 8 sets Class B requirements for slipping, failure, pull-apart and indentation (a test load Pind of 10,0 kN with Δ10 ≤ 1,5 mm), plus the Class B-only rotational and cruciform-bending requirements. A report that covers only slipping and failure does not support a Class B claim for that coupler. These are type-test requirements, not working loads. Check the edition too: a report written to EN 74-1:2022 before amendment A1:2025 predates the amended slipping evaluation rule (what a type test involves).

Why we insist on this order. During our own supplier checks in October 2026, a factory told us it stamps markings to whatever the customer asks for, while the type-test reports it holds covered Class A only. That is why we treat a class letter on a part as something to check against a report, never as proof.

If your supplier only has Class A

When the order says Class B and the factory’s evidence stops at Class A, there are three honest routes, and one that is not.

A test result above the Class B values in a Class A report does not turn the coupler into Class B. If the Class B-only requirements were not tested, the coupler has not been assessed as Class B.

What to ask the supplier for

Ask for these before a first order, and check them against each other:

1. The type-test report for the exact type and class on your order, showing the report number, the type and class tested, the edition it was written to, the date and the tightening condition (50 Nm torque wrench for screw couplers under BS EN 74-1:2022+A1:2025). A report for a different coupler type, or for Class A when you ordered B, does not count.
2. The report as the laboratory issued it. A translation made by the supplier, or by us, is not the report. If the copy you receive says it is a translation, ask for the original and verify it with the issuing laboratory.
3. The product manual, which under clause 13 names the assessor and carries the assessment statement.
4. The production-inspection letter. The clause 8 designation has an inspection field that can read L, M or X. Annex B, which is informative, describes L as the manufacturer’s own control and M as control supervised by an independent certification system. If you want M, write it into the designation and ask for the latest third-party inspection report. If a supplier quotes X, ask it, or the assessor, what X stands for and on what basis; we have not recorded a definition for it.
5. A marking check on a sample, after galvanising, to confirm the class letter matches the line on the order and the report.

For the rest of the order lines (finish, construction, quantity and tube), see the purchase-order list in the coupler types guide and the order checklist in the BS 1139 vs EN 74 guide.

Send a coupler specification with the type, class and edition for each coupler, and tell us which documents your project needs. We will tell you which of them a factory can actually show.

Frequently asked questions

▸What is the difference between Class A and Class B scaffold couplers?

In BS EN 74-1:2022+A1:2025 the class sets which type-test requirements a coupler prototype has to meet, and the meaning depends on the coupler type. For a right-angle (double) coupler, Table 8 requires a characteristic slipping force at 1–2 mm displacement of 10,0 kN for Class A and 15,0 kN for Class B, a failure force of 20,0 kN against 30,0 kN, and, for Class B screw couplers only, rotational and cruciform-bending requirements that Class A does not carry. For a sleeve coupler, the Class B-only requirement is a bending moment of 1,4 kNm. These are type-test values, not working loads.

▸Is a Class B coupler stronger than a Class A coupler?

Only within one coupler type and one edition. In BS EN 74-1:2022+A1:2025, a Class B swivel coupler has a failure-force requirement of 20,0 kN, while a Class B right-angle coupler has 30,0 kN, so 'Class B' does not name a single strength across types. The values are characteristic type-test requirements for a prototype; the load a coupler may carry in a scaffold comes from the scaffold design.

▸Can I supply Class A couplers when the order says Class B?

Not as a quiet substitution. We treat the class on an order as a design and specification input that the supplier should not change on its own. If only Class A is available, put that to the buyer in writing, state that the couplers are Class A, and in our practice proceed only once the buyer, and the person responsible for the scaffold design, have accepted Class A in writing.

▸Does an 'EN 74-1 Class B' mark on a coupler prove its class?

No. Clause 9 of BS EN 74-1:2022+A1:2025 requires the class letter to be impressed or embossed on the coupler, but the mark is applied by the manufacturer. What supports the class is the assessment for that coupler type and class, which clause 12 requires to be carried out by a person or organisation other than the coupler's designer, together with the product manual, which under clause 13 names the assessor and carries a copy of the assessment statement.

Sources

1. BS EN 74-1:2022+A1:2025 Couplers, spigot pins and baseplates for use in falsework and scaffolds — Part 1: Couplers for tubes (current edition; clauses 4.2.1, 6.2.1, 6.2.5, 7.2.1.5, 8, 9, 12, 13, Tables 2–6 and 8, Annex B). BSI product page — accessed 2026-09-17