‘An Evaluation of the Current Fire Safety Principles for the Design of Mass Timber Buildings in the UK’ by Ryan Collins

Trigon is proud that Ryan Collins has recently joined our team. Ryan completed his undergraduate degree in Civil Engineering at UCL University College London in 2022.

Today we are sharing some of his findings of his final thesis:  

‘An Evaluation of the Current Fire Safety Principles for the Design of Mass Timber Buildings in the UK’

Ryan Collins: “I began this research project with limited knowledge in the field of fire safety engineering. The title of this research project was something that immediately sparked my interest. Achieving fire-safe timber structures? This was a project I immediately knew was going to become very complex, very quickly.

The project began by discussing the need, and desire, to implement timber in large construction projects. Timber brings several benefits to such projects, for example, reducing construction times; offering a sustainable alternative to traditional construction materials, such as steel or concrete; and facilitating some of the most beautiful architectural designs. Despite these benefits, engineers are still sceptical about the use of timber in large-scale projects, in large part due to its complex interaction with fire. The use of timber in construction is on the rise, but its use in the UK is restricted by a lack of confidence in fire safety regulation when applied to timber structures. This project aimed to contribute to a better understanding of the behaviour of timber structures in fire and support the publication of better building codes and guidance in the future.

The main body of text commences by reviewing the current guidance on fire safety when designing structures within the UK. Particularly of focus is the Approved Document B (ADB) which is standard guidance in England and Wales for fire safety design. The project’s central focus, of which all modelling is based upon, is that of a conceptual residential structure developed by Waugh Thistleton Architects , that aims to capitalise on the shift to adopting timber in construction by “facilitating building regulations approval, construction and general building insurance applications, and warranty and mortgage applications”.

Recommendations within ADB are investigated, applicable for the design of a residential block of flats. This has been completed by comparing the Available Safe Egress Time (ASET), with the Required Safe Egress Time (RSET). This is the process of comparing the time it takes for the developing fire to reach a stage that deems the compartment uninhabitable, defined by ASET, and the time it takes for the occupant furthest from the final exit of the building to evacuate through said final exit. By being able to prove that occupants have sufficient time to evacuate from the location of a developing fire, before the conditions become untenable, brings about a level of confidence in the level of safety outlined in current guidance.

Through developing a zonal fire model and extracting values from a one-dimensional heat transfer model to determine the ASET and comparing these values with those from an occupant evacuation scheme for RSET values, a conclusion could be made for defined conditions of untenability throughout the duration of the fire about the level of safety. The modelling processes build on theories and standard guidance outlined in BS 7974. Given the potentially fatal consequences of not being safe, there should be absolute certainty in these conclusions. For example, we were able to find that the first condition of untenability being the time to flashover within the compartment of fire origin was occurred prior to occupant evacuation. Conversely, the following two untenability conditions being ignition of the primary timber lamella or first glue-line within the CLT, never occurred as temperatures did not reach sufficient levels before burnout of the fire.

Current state-of-the-art research and testing is not all encompassing to be able to answer all the relevant questions. Institutions and independent researchers continue to develop knowledge within this field to benefit the future of the wider construction industry. The aim of this work is to bring to light some of the challenges facing timber implementation in the fire safety industry.”

This work was completed alongside fellow graduate Wilhem Aquino and supervised by Prof Jose Torero .

Should you be interested in this topic and wish to speak to Ryan Collins about his thesis, please feel free to contact him directly. 

Photo by Marcus Lenk on Unsplash