New Guidance on fire safety in taller wooden buildings

Published: 03.10.25

Timber is transforming construction, but its fire behaviour challenges the very foundations of current safety methods. A new guidance chapter from a European collaboration highlights why performance-based design is so valuable, why self-extinguishment must be the ultimate goal, and why layered fire safety is the only robust strategy in the face of uncertainties.

Across Europe, architects and engineers are turning to timber to reduce the carbon footprint of construction. But as structural wood becomes more common in medium-rise and taller buildings, it also introduces fire behaviour that concrete and steel never did.

- People want to build with timber, but they don’t necessarily know how to deal with the fire safety challenges, says Ian Pope, Fire Safety Researcher at DBI (Danish Institute of Fire and Security Technology) and co-author of the chapter ‘Compartment Fire Dynamics in Taller Timber Buildings: Guidance for Performance-Based Fire Safety Engineering’.

The chapter was produced within the European COST Action CA-HELEN on holistic design of taller timber buildings, which brings together researchers from across Europe to share knowledge and develop new guidance.

- You can’t just assume that the old methods will work with a timber building, Ian Pope adds.

Standard fire curves and prescriptive rules were designed for non-combustible structures. In timber buildings, once the material is exposed, the structure itself becomes part of the fuel load. And it is not only load-bearing timber elements that matter. Exposed surfaces such as timber ceilings or walls can also accelerate fire growth and reduce evacuation time. Flames exiting through windows can be much higher, fire growth may accelerate, and assumptions about evacuation and intervention may no longer hold.

Designing for self-extinguishment

The guidance makes one point especially clear: The ultimate aim for tall buildings is to ensure that a fire eventually burns out on its own, even if timber is involved.

- Self-extinguishment is critical for taller buildings, where fire service intervention is more challenging, Ian Pope explains.

Achieving this, however, is far from straightforward. Several mechanisms can prevent self-extinguishment. If adhesives in cross-laminated timber lose strength under heat, large pieces may delaminate, exposing fresh wood. If the protective char layer flakes away, fresh timber is exposed. If plasterboard encapsulation fails, the timber underneath may keep feeding the flames.

The chapter does not offer a step-by-step recipe for ensuring self-extinguishment. Instead, it brings together current knowledge, points to the key phenomena that influence fire behaviour, and highlights where engineers need to be particularly cautious.

Fire safety in layers

Because no single safeguard is reliable on its own, the chapter underlines the need for redundancy. Sprinklers are effective in most cases, but they can fail. Encapsulation provides protection but it must be robust enough to survive a real fire.

- You don’t want to design a building where everything goes wrong if the sprinkler system fails, Ian Pope stresses.

Layered fire safety means combining multiple measures, so that the failure of one does not compromise the whole building. Robustness and conservatism are key: Design must anticipate worst-case scenarios, not assume best-case outcomes.

The guidance chapter is part of a broader European COST Action on taller timber buildings. It does not claim to solve all problems, but to collect dispersed knowledge and provide a digestible starting point for practitioners. At the same time, it points to areas where answers are still missing: the real-fire performance of adhesives under load, the reliability of encapsulation in practice, and the impact of external flames when timber compartments burn.

As Ian Pope concludes:

- Even though we point to information, the higher the uncertainties, the more conservative you need to be. However, our knowledge and methods of optimisation are developing rapidly.

Read the chapter Compartment Fire Dynamics in Taller Timber Buildings: Guidance for Performance-Based Fire Safety Engineering