Welcome — this is a guided walkthrough of EN 1090 (Parts 1 and 2) and the Irish S.101 spec. We'll go through six short modules, then a 20-question self-scored exam that starts easy and builds up. Here's the first module.

Module 1: EN 1090 — What it is & what it covers

Module one: an overview of EN 1090. EN 1090 is the European standard for the execution of steel and aluminium structures. Part 1 covers conformity assessment of components, the basis for CE marking. Part 2 covers the technical requirements for steel structures, and Part 3 covers aluminium. Part 1 does not contain the design or manufacture rules itself. It points to the Eurocodes for design, and to Parts 2 and 3 for execution. Part 2 applies to structures designed to EN 1993 and expresses all its requirements in terms of execution classes.

Module 2: What counts as a 'structure' under EN 1090

Module two: what counts as a structure. EN 1090 works at three levels. A constituent product is the raw material, like a steel section or plate. A structural component is a load-bearing part made from those products. A structural kit is a set of components assembled and installed on site, and the assembled system of components is what the standard calls a structure.

Module 3: Certification required & execution classes (EXC)

Module three: certification and execution classes. Steel structural components must be CE marked under EN 1090-1, using attestation of conformity system two plus: the manufacturer runs initial type testing and factory production control, and a notified body certifies the factory production control. Execution classes are central. Part 2 defines four classes, EXC1 to EXC4, with strictness increasing from one to four. If no class is specified, EXC2 applies by default. As a rule of thumb, EXC2 suits buildings and EXC3 suits bridges. The S.101 agricultural spec adds its own layer: a Declaration of Performance for each building, and the contractor certified to at least execution class one.

Module 4: What is excluded / exempt from EN 1090

Module four: exclusions and exemptions. A wording note first: EN 1090-1 doesn't talk about exempt members. It states its scope, lists items outside that scope, and sets out cases where re-evaluation isn't needed. Part 1 does not cover components for suspended ceilings, or rails and sleepers for railway systems. Part 2 does not cover watertightness or air-permeability of sheeting. And components already CE marked to a harmonised standard can be presumed to have their stated performance, so they don't need re-testing.

Module 5: What shed is exempt from engineer sign-off (S.101)

Module five: shed exemptions under S.101. Here's the key correction. S.101 does not exempt sheds by floor area or square metres. The exemption from a chartered engineer's design depends on staying within set limits for eaves height, roof slope and span. For a simple steel frame, that's a maximum eaves height of five metres and a roof slope between twelve and fifteen degrees, with spans taken from the standard tables. Exceed any one of those, and a chartered engineer must prepare full design drawings and calculations for departmental approval.

Module 6: Welding — procedures, qualifications & quality

Module six: welding. EN 1090-2 sets out how welding must be planned, qualified and accepted. First, a welding plan is required as part of the quality management to EN ISO 3834. Welding must be carried out using a qualified welding procedure specification, a WPS, to EN ISO 15609 — the qualification method depending on execution class, parent metal and degree of mechanisation. Welders themselves are qualified to EN 287-1, and welding operators to EN 1418. For execution classes two, three and four, welding coordination by suitably qualified personnel to EN ISO 14731 is mandatory. Finally, finished welds are accepted against quality levels in EN ISO 5817, matched to the execution class: D for class one, C for class two, B for class three, and B-plus for class four.

Exam time — 20 questions, getting tougher as we go. For each: think of your answer, reveal the model answer, then rate yourself honestly. Your grade is tallied at the end.

In a sentence, what is EN 1090?