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PD 06705 — Structural Use of Steel and Aluminium BS EN 1090 Execution Recommendations Standard Series (PD 6705)
Recommendations for the Use of BS EN 1090 — Steel and Aluminium Structures (Published Document series)
📐 PD 6705 is a British Standards Institution (BSI) “Published Document” (PD) series providing “recommended selections” and non-contradictory complementary information (NCCI) for the UK application of BS EN 1090 (Execution of steel and aluminium structures). BS EN 1090-2 and BS EN 1090-3 cover execution of steel and aluminium structures respectively, containing many “options” to be decided by the designer/specifier. PD 6705 provides recommended UK practice for these choices. This batch collects two parts: Part 2 (PD 6705-2:2010+A1:2013) is the recommended selections permitted by BS EN 1090-2 (steel), and Part 3 (PD 6705-3:2009) is the recommendations for the use of BS EN 1090-3 (aluminium).
💡 Under the EU Construction Products Regulation (CPR), load-bearing steel structures must bear CE marking and comply with BS EN 1090. PD 6705 helps designers and manufacturers make safe, economical UK recommended selections among the options and execution classes (EXC) of BS EN 1090, with quantified classification methods.
1. Series Overview and Positioning 📌
PD 6705 is the responsibility of BSI Technical Committee B/525/31 (Execution of steel and aluminium structures); its parts correspond to different sub-parts of BS EN 1090: Part 2 addresses BS EN 1090-2 (steel structure execution), Part 3 addresses BS EN 1090-3 (aluminium structure execution).
This batch contains the following two parts:
| Document | Subject | Edition | Companion standard | Core content |
|---|---|---|---|---|
| PD 6705-2:2010+A1:2013 | Recommended selections permitted by BS EN 1090-2 (steel) | 2010+A1:2013 | BS EN 1090-2:2008+A1:2011 | Specifications and documentation, steel products, preparation and assembly, welding, bolting, erection, surface treatment, geometrical tolerances, inspection and NDT |
| PD 6705-3:2009 | Recommendations for the use of BS EN 1090-3 (aluminium) | 2009 | BS EN 1090-3 | Service category and execution classes, specification and documentation, constituent products, preparation, welding, mechanical fastening and adhesive bonding, corrosion protection, inspection and corrections |
⚠️ PD 6705 gives “recommendations” (should), not replacing the “requirements” (shall) of BS EN 1090. Designers must first satisfy the mandatory clauses of BS EN 1090 (including the EU CE marking framework) and then adopt the recommended selections of PD 6705.
2. Steel Structure Recommended Selections (Part 2) 🔧
Part 2 gives UK recommended selections for the optional clauses of BS EN 1090-2, with main sections including:
- Specifications and documentation (Clause 4): recommended practice for execution documents, technical specifications and declarations of conformity.
- Steel products (5): grade selection, inspection documents and material traceability.
- Preparation and assembly (Clause 6): cutting, forming, drilling and assembly.
- Welding (Clause 7): welder qualification, welding procedure qualification (WPS/PQR), weld inspection.
- Bolting (Clause 8): hole type (slotted-hole method), bearing and friction connections, preloading (torque method and part-turn method).
- Erection, surface treatment, geometrical tolerances (Clauses 9/10/11): site erection, painting and permitted deviations.
- Inspection, testing and correction (7.6 and Clause 12): including minimum extent of supplementary NDT (Tables 4/5/6, by steel grade and quantified service category F56 etc.).
Annex B gives the method of determination of the quantified service category and guidance for designation on drawings (Figures F71 to F140); Annex C gives explanatory notes on selected recommendations (e.g. definition of stress-raising zones for machine plasma cut edges).
2.1 Quantified Service Category and Torque Control
Part 2 quantifies the “service category” (e.g. F20, F56) to determine the proportion of supplementary NDT and weld acceptance criteria. For preloaded bolts, it gives torque/rotation values for the part-turn method (Tables 2, 3) to control preload.
3. Aluminium Structure Recommendations (Part 3) 🛠️
Part 3 gives UK recommendations for the use of BS EN 1090-3:
- Service category and execution classes: recommend EXC selection and application of quantified service categories (F20, F25 to F63, etc.).
- Specification and documentation, constituent products: requirements for aluminium sections, plates and connections.
- Preparation and welding: the particularities of aluminium welding (porosity control, heat input), weld acceptance criteria (visual/penetrant/ultrasonic).
- Mechanical fastening and adhesive bonding: fastening and bonding requirements differing from steel (part-turn torque/rotation values, Tables 2/3).
- Corrosion protection, inspection and corrections: surface protection and inspection procedures for aluminium structures.
💡 Aluminium welding differs significantly from steel: aluminium conducts heat quickly and is prone to porosity and hot cracking, requiring dedicated procedure qualification and NDT criteria. PD 6705-3 gives, for EXC2, the minimum proportion of supplementary NDT for alloys other than 7***, with visual/penetrant/ultrasonic acceptance criteria.
4. Engineering Practice Points ⚙️
- 🔍 CE marking and EXC: determine the execution class (EXC1-EXC4) per CPR and BS EN 1090, then adopt the PD 6705 recommended service-category parameters.
- 🔧 Welding management: execute WPS/PQR, welder qualification and supplementary NDT determined by the quantified service category.
- 📊 Bolt preloading: for preloaded bolts use the part-turn method, controlling preload by the torque and rotation in Tables 2/3.
- 📋 Documentation and traceability: mark the service category on drawings (F71-F140) and retain material certificates and inspection records.
5. Frequently Asked Questions ❓
❓ Q: What is the relationship between PD 6705 and BS EN 1090?
A: PD 6705 provides UK recommended selections and complementary information (NCCI) for the optional clauses of BS EN 1090-2/3, without replacing the mandatory requirements; satisfy the mandatory clauses first, then adopt the recommendations.
A: PD 6705 provides UK recommended selections and complementary information (NCCI) for the optional clauses of BS EN 1090-2/3, without replacing the mandatory requirements; satisfy the mandatory clauses first, then adopt the recommendations.
❓ Q: What is a quantified service category?
A: Quantifying the “service category” into an F value (e.g. F20, F56) determines the minimum proportion of supplementary NDT and weld acceptance criteria — a tool balancing welding quality and cost.
A: Quantifying the “service category” into an F value (e.g. F20, F56) determines the minimum proportion of supplementary NDT and weld acceptance criteria — a tool balancing welding quality and cost.
❓ Q: How to choose between Parts 2 and 3?
A: Use Part 2 (PD 6705-2) for steel structures, Part 3 (PD 6705-3) for aluminium structures. The material properties differ, so welding, fastening and corrosion-protection requirements differ.
A: Use Part 2 (PD 6705-2) for steel structures, Part 3 (PD 6705-3) for aluminium structures. The material properties differ, so welding, fastening and corrosion-protection requirements differ.
🔍 Q: What is the relationship between CE marking and BS EN 1090?
A: Under the EU Construction Products Regulation (CPR), load-bearing steel structures must bear CE marking and their execution must comply with BS EN 1090. PD 6705 helps make recommended selections among the standard options and execution classes to support compliance.
A: Under the EU Construction Products Regulation (CPR), load-bearing steel structures must bear CE marking and their execution must comply with BS EN 1090. PD 6705 helps make recommended selections among the standard options and execution classes to support compliance.