BSI have published a new version of BS EN 1991-1-4:2026. This version supersedes BS EN 1991-1-4:2005+A1:2010.
Note, as part of the standards development process, the 2026 version is currently being reviewed, with a draft at the public comment stage. This is expected become BS EN 1991-1-1-4:2026+A1 and it is anticipated that this will be published soon.
It should be noted that, as per the forward of the standard that “The UK abstained because the UK committees wanted Annex B, Annex C and Annex D to be informative rather than normative, thereby providing greater national choice in relation to material on aerodynamic coefficients.” Despite this, as a member of CEN, BSI is obliged to publish any revised standard.
As is the usual approach when new versions are released, there is presently a coexistence period where both the 2005 and new 2026 version are considered ‘current’. This period provides time for parties to familiarise themselves with the new version, update specifications and similar. It should also be noted that the National Annex (NA) to the 2005 version does not automatically carry forward to the 2026 version so, as of this publication, there isn’t a NA to the 2026 version available.
Further information on the publication of new versions of British Standards can be found here.
Key changes include:
CWCT have undertaken an initial high-level review of BS EN 1991-1-4:2026, which has introduced a number of changes relevant to façade and building-envelope design.
One of the most notable changes is the introduction of external global pressure coefficients, intended for determining overall actions. The coefficients applicable to components are now explicitly referred to as external local pressure coefficients, providing a distinction between overall structural wind actions and the pressures used for the design of cladding panels, glazing and other envelope components.
For vertical walls, the definition of vertical zoning used to establish reference heights has been revised, including specific provisions relevant to cladding. There are also some changes to the external local pressure coefficients themselves, for example for duo-pitch roofs, although most of the coefficients of envelope-relevant models are unchanged.
The scope of application has also been extended to up to 300 m, as an alternative wind model for slender systems is now incorporated; refer to Annex A. In the previous standard, the exposure factor diagram was provided only up to 100 m. It was extended to 200 m in the National Annex, and this extension is now incorporated into the updated standard.
The standard also recognises the increasing use of advanced wind-engineering methods. The revision provides a framework for using information from wind-tunnel testing (WTT), numerical simulations, or in other words computational wind engineering (CWE) and meteorological measurements, together with probabilistic models to wind actions, through new Annexes J, K and L.
The revised standard provides considerably more guidance for complex, tall and dynamically sensitive systems and components. The structural factor cₛcd is determined using a revised procedure in Annex E. The across-wind and torsional actions on susceptible buildings are addressed in Annex F, and further aeroelastic response is covered in Annex G. Aerodynamic coefficients have also been added for a wider range of structural forms. For façade engineering, these provisions will be particularly relevant to designs with uneven geometry, shapes, stiffness or to any slender components under aerodynamic excitation.
Finally, the revised standard includes the effects of wind on ice-accreted elements, further broadening the range of situations addressed, particularly relevant to sloped facades, roofs and canopies.