Since the publication of the first edition of this guide, substantial regulatory changes have been implemented in the 2020 edition of the National Building Code of Canada: the addition of encapsulated mass timber construction up to 12 storeys, and the early adoption of the related provisions by several provinces are the most notable ones. The 2022 edition of this guide brings together, under one cover, the experience gained from recently built tall wood projects, highlights from the most recent building codes and standards, and research findings to help achieve the best environmental, structural, fire, and durability performance of mass timber products and systems, including their health benefits. The approaches to maximizing the benefits of prefabrication and building information modelling, which collectively result in fast, clean, and quiet project delivery, are discussed. Methods for addressing limitations controlled by fire requirements (through an Alternative Solution) or seismic requirements (through a hybrid solution using an Acceptable Solution in steel or concrete) are included. How best to build with mass timber to meet the higher performance requirements of the Energy Step Codes is also discussed. What makes building in wood a positive contribution toward tackling climate change is discussed so that design teams, in collaboration with building owners, can take the steps necessary to meet either regulatory or market requirements.
The building industry consumes a lot of material, which causes depletion of material stocks, toxic emissions, and waste. Circular building design can help to reduce this impact, by moving from a linear to a circular design approach.
To reach a circular build environment, all disciplines should be involved, including fire safety design. However, there is a contradiction between the objectives of circular and fire safety design, either affecting the aim of protection of material sources, or protection against fire risk.
Timber is a material that has high potential in contributing to a circular building industry, as it is renewable, recyclable and can store CO2. However, timber is combustible, which increases the risk of fire. Therefore, mass timber building design has traditionally been restricted by building regulations. To enhance mass timber building design research on timber buildings has increased, to allow understanding of the risks. However, yet general guidelines or understanding on the fire behaviour and risk in timber buildings is lacking. This is a problem for the fire safety design and the potentials of timber contributing to a circular building industry.
Until now, there was no specific method available that quantifies this relation between material use and fire risk in mass timber buildings. This limits the possibility of fire safety design and mass timber design to contribute to a more circular building industry. By creating a method that allows comparison between the economic and environmental impact of material use and fire risk, a well-founded choice of building materials is easier to make.
The design tool created in this research quantifies the impact on material use for fire safety measures relating to CLT, encapsulation and sprinkler availability and their effect on the fire risk in mass timber buildings. This way insight is provided between the balance of material use and fire risk. By the sum of the impact on material use and fire risk, the total “circular fire safety impact” value is calculated. This value represents the total economic and environmental impact of the design based on the choice of building materials. By changing the fire safety design, the most optimal design variant can be determined. This is the variant with the lowest total impact value.
This way, a circular design approach is used to steer fire safety design in mass timber buildings towards a design solution that does not only provide sufficient safety for people, but also provides maximum economic and environmental safety from a material point of view.
Wood is commonly used in construction, but often perceived as being less safe than structures made from non-combustible materials. With the advancement of wood products and treatment, construction techniques, and protective systems, this may not be the case any longer. Using retrospective data from fire departments across Canada, this study aimed to determine whether the type of construction material (combustible or non-combustible) affected the fire severity outcome of a one to six storey apartment building fire, after accounting for protective systems (smoke alarms and sprinklers). The study found that, after adjusting for the presence of smoke alarms and sprinklers, structures constructed from non-combustible construction materials did not perform better in terms of injuries, requiring extinguishment by fire department, or the fire spreading beyond the room of origin. The presence of working smoke alarms and sprinklers played a central role in reducing the severity outcome of a fire. Smoke alarms and sprinklers both reduced the odds of extinguishment by the fire department and the fire spreading beyond the room of origin. Sprinklers also reduced the injury rate. Overall, this study highlighted the importance of protective systems in reducing fire severity outcomes.
This paper describes selected observations, measurements, and analysis from a series of large-scale experiments on cross-laminated timber (CLT) slabs that were exposed to fire from below, using four different heating scenarios, with a sustained mechanical loading of 6.3 kN m per metre width of slab. The deflection response and in-depth timber temperatures are used to compare the experimental response against a relatively simple structural fire model to assess the load bearing capacity of CLT elements in fire, including during the decay phase of natural fires. It is demonstrated that the ventilation conditions in experiments with a fixed fuel load are important in achieving burnout of the contents before structural collapse occurs. A mechanics-based structural fire model is shown to provide reasonably accurate predictions of structural failure (or lack thereof) for the experiments presented herein. The results confirm the importance of the ventilation conditions on the fire dynamics, burning duration, and the achievement of functional fire safety objectives (i.e. maintaining stability and compartmentation), in compartments with exposed CLT.
An advanced modelling tool, WoodST, has been developed for fire safety analysis of timber structures. It is demonstrated that this advanced modelling tool can predict the structural response of LVL beams, glulam bolted connections, OSB-web I-joist and wood-frame floors under forces and fire conditions with an accuracy acceptable to design practitioners (i.e., within 10% of test data). The developed modelling tool can:
Fill the gap in terms of suitable models for timber connections, which is an impediment for the design and construction of tall wood buildings;
Provide a cost-effective simulation solution compared to costly experimental solutions; and
Significantly reduce the cost and shorten the time for the development and/or optimization of new wood-based products and connections.
This study investigates five fire stop variants used to limit the spread of fire on wooden façades. For this purpose, five fire tests using various types of wooden façade claddings and different fire stops were conducted as full-scale tests and compared to the existing findings. The influences and interactions between the material qualities of the external wall behind the façade cladding, the construction type of the wooden façade cladding, the design of the substructure, the depth of the ventilation gap, and the design of the fire stops were investigated. In evaluating the fire stops, the design of the interior corners, the joint design, and the influence of thermal expansion were examined. Finally, design proposals for the design of fire stops at wooden façades in order to limit the spread of fire were derived based on this evaluation. The outlook presents further needs that need to be investigated in the future in order to clarify undiscussed aspects or points that were ultimately not evaluated within the scope of this study.
The possibilities for building in wood have gradually increased in recent decades mainly due to environmental benefits. But there are still restrictions in terms of fire regulations in many countries, especially for taller buildings. The situation has therefore been mapped in about 40 countries on four continents as an update to a survey in 2002. The main issues are how high buildings with load-bearing wooden frames may be built and how much visible wood may be used both inside and outside on facades. The restrictions apply primarily to prescriptive fire design according to simplified design with detailed rules, which are mainly used for residential buildings and offices. For more complicated constructions e.g. public buildings, shopping centers, arenas and assembly halls, performance based design can be used by fire safety engineering design using, e.g. methods for evacuation and smoke filling, which increases the possibilities of using wood in buildings. The possibilities to use wood in buildings increase if sprinklers are installed, which is highlighted. Major differences between countries have been identified, both in terms of the number of storeys permitted in wood structures, and of the amounts of visible wood surfaces in interior and exterior applications. Several countries have no specific regulations, or do not limit the number of storeys in wooden buildings. The conclusion is that the differences are still large and that many countries have not yet started to use larger wood constructions despite supplies of forest resources, but harmonizing activities on performance based principles are ongoing worldwide.
Fire safety regulations impose very strict requirements on building design, especially for buildings built with combustible materials. It is believed that it is possible to improve the management of these regulations with a better integration of fire protection aspects in the building information modeling (BIM) approach. A new BIM-based domain is emerging, the automated code checking, with its growing number of dedicated approaches. However, only very few of these works have been dedicated to managing the compliance to fire safety regulations in timber buildings. In this paper, the applicability to fire safety in the Canadian context is studied by constituting and executing a complete method from the regulations text through code-checking construction to result analysis. A design science approach is used to propose a code-checking method with a detailed analysis of the National Building Code of Canada (NBCC) in order to obtain the required information. The method starts by retrieving information from the regulation text, leading to a compliance check of an architectural building model. Then, the method is tested on a set of fire safety regulations and validated on a building model from a real project. The selected fire safety rules set a solid basis for further development of checking rules for the field of fire safety. This study shows that the main challenges for rule checking are the modeling standards and the elements’ required levels of detail. The implementation of the method was successful for geometrical as well as non-geometrical requirements, although further work is needed for more advanced geometrical studies, such as sprinkler or fire dampers positioning.
The vulnerability of any building, regardless of the material used, in a fire situation is higher during the construction phase when compared to the susceptibility of the building after it has been completed and occupied. This is because the risks and hazards found on a construction site differ both in nature and potential impact from those in a completed building; and these risks are occurring at a time when the fire prevention elements that are designed to be part of the completed building are not yet in place. For these reasons, construction site fire safety includes some unique challenges. Developing an understanding of these hazards and their potential risks is the first step towards fire prevention and mitigation during the course of construction (CoC).
The objective of this work is to generate fire resistance data for NLT assemblies to address significant gaps in technical knowledge. This research will support designers and builders in the use of mass timber assemblies in larger and taller buildings, as well as provide scientific justification for Authorities Having Jurisdiction (AHJ) to review and accept this construction method. The intent is to demonstrate that NLT construction can meet or exceed NBCC fire safety requirements for use in buildings of mass timber construction.
The data could be used towards the inclusion of an NLT fire resistance calculation methodology into Annex B of CSA 086 - Engineering Design for Wood, which currently addresses only glue-laminated timber (GLT), structural composite lumber (SCL) and cross-laminated timber (CLT).