As engineers why do we refrain from using timber in residential and office floors? Apart from potential fire and durability concerns that we know can be overcome through well considered detailing, it can often come down to our worries with the vibration performance. But this shouldn’t be the case – we know that a vast number of historic buildings, now used as office spaces have timber floors (including our Studio!) that have no perceivable vibration issues. The current Eurocode 5 however compounds our worries as designer. It is limited in scope only offering that you should design timber to achieve at least a natural frequency of 8Hz, while offering no guidance on response factors.
At P&M we have had a recent resurgence in the proposed use of timber floors in residential and office spaces, driven by the desire to use less carbon intensive materials. But this has begged the question, how do we justify the vibration performance of said floors and ensure these carbon savings are made? In steps the saviour, revised Eurocode 5, currently in its draft form and due for release in 2025, that offers the designer clearer and more comprehensive information for the design of timber floors in vibration. Its main changes in scope include:
- The ability to assess floors with a natural frequency below 8Hz. Previously, heavier floors that inherently achieve lower natural frequencies such as maybe a CLT floor with a concrete screed, would be deemed unsuitable by the current standards.
- The introduction of vibration performance levels. The guides offers three levels of performance for engineers to design: Quality, Base and Economy.
- A new method to calculate response based on velocity. Most vibration designers are used to calculate their response factors based on acceleration. However, the revised Eurocode 5, adopts a velocity-based approach to calculate response factor for high frequency floors.
We hope our ability to accurately assess the vibration performance of timber floors, with the use of the revised Eurocode 5, will help further encourage the revival of timber floors in the future, by giving clients and design teams confidence on the performance of their floors.
Please note that this article is based on the DRAFT form of Eurocode 5 and assumes it will remain largely unchanged on release.
