Review of fire experiments in mass timber compartments: Current understanding, limitations, and research gaps

Abstract

The use of mass timber in buildings instead of non‐combustible materials has benefits in sustainability, aesthetics, construction times, and costs. However, the uptake of mass timber in modern construction for medium and high‐rise buildings is currently hindered by uncertainty regarding safety and structural performance in fire. We attribute this to a lack of data. Insufficient understanding means that for building designs beyond the current range of experiments the fire performance is unknown. To address this uncertainty, we review the available data in the scientific literature from 63 compartment fire experiments with timber, the majority of which use cross‐laminated timber (CLT). We found that most experiments reached temperatures 80–180°C greater than in non‐combustible compartments. Timber ceilings have on average a 16% lower char rate than timber walls. The heat release rate contribution of timber has a positive linear relationship with charring rate, however is susceptible to significant uncertainty and variability. There are limits to the data available, particularly in large open‐plan compartments of floor areas larger than 100 m2 where a wider range of heating conditions occur. Other topics where further understanding is required are compartments with exposed timber areas greater than 75%, compartments with smaller opening areas, and the hazard of smouldering following the flames. Therefore, additional research is needed to design beyond the limits, specifically in compartment size, ventilation, and timber exposure. This paper identifies correlations in the current body of experimental research to improve fire‐safe design of timber buildings.

External fire plumes from mass timber compartment fires—Comparison to test methods for regulatory compliance of façades

“…7 However, for the safe development of mass timber structures, fire safety concerns associated with an inherently combustible material must be addressed. 8 One such concern is its effects on the external façade. It is highly likely 9 that exposing mass timber surfaces leads to longer fire exposure and that exposed surfaces increase release of pyrolysis gases combusting when mixing with air along the external façade if the fire is ventilation limited.…”

“…Multi‐storey mass timber compartments, appealing with their low carbon footprint, aesthetic signature and residential wellbeing when visibly exposing the wooden structure, are being built at an accelerating rate 7 . However, for the safe development of mass timber structures, fire safety concerns associated with an inherently combustible material must be addressed 8 . One such concern is its effects on the external façade.…”

Full-Scale Fire Experiments on Cross-Laminated Timber Residential Enclosures Featuring Different Lining Protection Configurations

“…Large-scale fire experiments on mass timber enclosures have developed into an area of significant study given the global proliferation of buildings using wood as the primary framing material. It is not the intent in this paper to undertake an extensive review of existing literature on the topic, with several review studies having been undertaken in the last decade, by Buchanan et al [20], Brandon and O ¨stman [21], Ronquillo et al [22], Liu and Fischer [23], Mitchell et al [24], Bøe et al [25,26] and Su et al [27]. However, what these review papers collectively highlight is a lack of knowledge on the role of different lining protection strategies for CLT residential buildings on the prospect of self-extinction and, in the authors' opinion, a conflating of fire dynamics behaviours that arise due to fire induced delamination versus failure/fall-off of fire protection materials, such as secondary or tertiary flashovers.…”

Fire research for timber structures

“…The first article includes a review of 63 compartment fire tests including timber structures regarding temperature development and charring behaviour 1 . In the reviewed material, timber ceilings had on average a 16% lower charring rate than timber walls and the peak temperatures in most experiments were higher than non‐combustible compartments.…”