Construction Fixings

By Barbara Sorgato, secretary general, European Consortium of Anchor Producers (ECAP)

The EN Eurocodes are a series of ten European Standards, EN 1990 – EN 1999, providing a common approach for the design of buildings and other civil engineering works and construction products. They are adopted by several Member States as the National Building Codes and are the recommended reference for technical specifications in European public contracts.

In 2012, the European Commission issued the Mandate M/515 for a detailed work programme for amending existing Eurocodes and extending the scope of structural Eurocodes. The work of the second generation of Eurocodes is almost ready, formal votes will be concluded by early 2026 and the definitive text in the official language versions (English, German and French) will be distributed no later than 30^th March 2026. Member States are due to implement Eurocodes by 30^th September 2027 by publication of an identical national standard or by endorsement. The actual Eurocodes, and any related national standards conflicting with the new generation Eurocodes, have to be withdrawn by 30^th March 2028. This explains the attention and the involvement of many experts in the drafting of Eurocodes.

The key developments of the new Eurocodes include improving the practical use of Eurocodes for day-to-day calculations; introducing requirements for the assessment, reuse and retrofitting of existing structures; as well as the strengthening of requirements for robustness.

Focusing on the timber sector, Eurocode 5 ‘Design of timber structures’ faced a number of challenges, such as the tremendous development of timber structures in the last 30 years; the development of timber concrete composite structures; the need of harmonisation within the whole Eurocode family; the interface with product standards and European Assessment Documents (EADs); as well as the alternative design methods developed outside of Eurocodes.

In fact, the chapter on connections has seen a variety of new connection types covered by product standards stuck in the pipeline of the standardisation blockage or dealt by EADs. Some product standards and some EADs, in view of the revision of Eurocodes, dealt with topics such as seismic provisions, durability, sustainability, and related design – somehow anticipating the Eurocodes. 

The amended versions of the Eurocodes were then taking on board these aspects, developing them further – as in the case of durability, addressed first in the standard on timber connectors EN 14592:2020 and developed in a more articulated way in Eurocode 5. 

Moreover, the Eurocodes also had to reflect several concepts of the new Construction Products Regulation – whose final text is now available – such as installation (execution), sustainability (reuse and retrofitting) and harmonised zone (accessible only via harmonised standards and not anymore via European Technical Assessments). 

All these changes generated intensive discussions of both technical and general nature in all Eurocodes. In its enquiry phase, which is the phase where Member States are allowed to comment on the final text, Eurocode 5 alone received in total 7,130 comments, 1,397 of which were on the chapter ‘connections’. 

Imagine the stress in the management group who is now seeking for consensus on the most disputed comments. Some of the comments that addressed specific concerns of manufacturers of European timber connectors included:

Categories on woodscrews

Manufacturers expressed concerns, and basically opposed, the introduction of screw categories in the Eurocode. The fear is that woodscrews could become a sort of metric product.

New formulation for slip modulus of screws

At a more technical level, manufacturers expressed concerns on the new formulation for slip modulus of screws, which penalises significantly connections featuring a high-density timber member, and on the value 7.5 given for screws.

Use of specific ETA values

In the new Eurocode 5, the use of specific ETA values as an alternative to calculation methods in Eurocodes is allowed only if these are referred to and addressed by the Eurocodes on a case by case basis. 

The Eurocode management made it clear that users who apply other information than (a) default values specified in the Eurocode itself for the calculation or (b) the properties and values specified in the relevant, by the Eurocodes referred documents, are exceeding the scope of the design standard. They are, in fact, outside of Eurocodes’ jurisdiction. Hence, responsibility for the applicability of those used values is then transferred to the user. Manufacturers that did not manage to include alternative ETA values in the Eurocodes are now concerned this may undermine their ETAs and may manifest costs to reissue them.

Specific execution rules

The introduction of very specific execution rules, which can be seen as forcing users to adopt procedures that are not usual in some member states. One must remember that construction is a very conservative branch, based on local building traditions.

Seismic provisions for timber screws

The introduction of seismic provisions for timber fasteners, which were introduced in Eurocode 5 and then transferred to Eurocode 8. Although seismic design is mandatory for certain Member States, it is sometimes seen as a hidden barrier to trade by manufacturers from Member States that are not familiar with the requirements requested by this design (e.g ductility).

Manufacturers of timber fasteners are meeting to discuss and share their analysis and efforts to try to influence some last minutes changes. 

It will be important to see how the new design code will be implemented in the related harmonised standards and what will happen with the many ETAs on timber products. This topic is very much depending to the content of the new CPR, which now requires an in-depth analysis and guidance to help manufacturers and users understand what is going to change in the next few years.