Five full-scale fire experiments were conducted to observe the performance of a two-level apartment-style structure constructed of mass timber. Each level consisted of a one bedroom apartment, an L-shaped corridor, and a stairwell connecting the two levels. One of the primary variables considered in this test series was the amount and location of exposed mass timber. The amount of mass timber surface area protected by gypsum wallboard ranged from 100% to no protection. For each experiment, the fuel load was identical and the fire was initiated in a base cabinet in the kitchen. In the first three experiments, the fire reached flashover conditions, and subsequently underwent a cooling phase as the fuel load from combustible contents was consumed. The first three experiments were carried out for a duration of up to 4 h. In the fourth experiment, automatic fire sprinklers were installed. Sprinklers suppressed the fire automatically. In the fifth experiment, the activation of the automatic fire sprinklers was delayed by approximately 20 minutes beyond the sprinkler activation time in the fourth experiment to simulate responding fire service charging a failed sprinkler water system. A variety of instrumentation was used during the experiments, including thermocouples, bidirectional probes, optical density meters, heat flux transducers, directional flame thermometers, gas analyzers, a fire products collector, and residential smoke alarms. In addition, the experiments were documented with digital still photography, video cameras, and a thermal imaging camera. The experiments were conducted in the large burn room of the Bureau of Alcohol, Tobacco, Firearms and Explosives Fire Research Laboratory located in Beltsville, Maryland, USA. This report provides details on how each experiment was set up, how the experiments were conducted, and the instrumentation used to collect the data. A brief summary of the test results is also included. Detailed results and full data for each test are included in separate appendices.
Concealed spaces, such as those created by a dropped ceiling in a floor/ceiling assembly or by a stud wall assembly, have unique requirements in the International Building Code (IBC) to address the potential of fire spread in nonvisible areas of a building. Section 718 of the 2018 IBC includes prescriptive requirements for protection and/or compartmentalization of concealed spaces through the use of draft stopping, fire blocking, sprinklers and other means.
Fire Performance Requirements of Non-Load-Bearing Wood-Frame In-Fill Walls in Concrete/Steel Hybrid Buildings. Part 2 - Review of the National Building Code of Canada
This project evaluates the National Building Codes of Canada (NBCC) clauses relevant to fire performance and performance requirements of non-load-bearing wood-frame in-fill walls in concrete/steel hybrid buildings. Related clauses in NBCC are reviewed regarding the use of wood components and non-load bearing wall systems in non-combustible buildings. The highlights of this review are:
§ An exterior non-loadbearing wall assembly with combustible components is allowed in non-combustible construction if:
a) Building height is not more than 3 storeys or has a sprinkler system throughout ;
b) The interior surfaces of the wall assembly are protected by a thermal barrier ; and
c) The wall assembly satisfied the testing criteria for CAN/ULC S134 ;
§ Combustible interior wall finishes, other than foamed plastics, are allowed in non-combustible construction if the thickness is not greater than 25 mm and their flame spread rating (FSR) is not more than 150 ;
§ Combustible insulation, other than foamed plastics, is allowed in non-combustible construction if the flame-spread rating not more than 25 ;
§ Combustible insulation with a FSR not less than 25 and not more than 500 is allowed in exterior and interior walls of non-combustible construction if the building is non-sprinklered and not more than 18 m or sprinklered and protected by a thermal barrier ;
§ There are no obstacles for using wood-frame in-fill wall systems for interior partition walls in hybrid buildings:
a) For non-sprinklered buildings not greater than 3 storeys or a floor area not greater than 600 m2 ;
b) For sprinklered buildings.
§ Non-combustible construction allows combustible elements in partition walls in the following instances:
a) Solid lumber partitions located in a fire compartment area are permitted in a non-sprinklered floor area not greater than 600 m2 with restrictions ;
b) Solid lumber partitions not less than 38 mm thick and partitions that contain wood framing are permitted with restrictions.
§ Combustible cladding can be used under the following circumstances:
a) When a wall assembly with exposing building face is between 10 to 25% tested by CAN/ULC-S134 and complies with Article 3.1.5.5 ;
b) When a wall assembly with exposing building face is between 25 to 50%, is sprinklered throughout, installed on a gypsum board sheathing, and has a FSR not more than 25 (with restrictions) ;
c) When a wall assembly with exposing building face is between 50 to 100%, cladding can be combustible for group A, B, C, D, E, F.
§ When a building is required to be of non-combustible construction, combustible elements are limited to the requirements in Subsection 3.1.5 on non-combustible construction ;
§ When comparing the NBCC with the International Building Code (IBC), the IBC is more in favour of using FRT wood frame in-fill walls with one more storey.
"This report presents the findings from a simulation parametric study to investigate the use of water mist systems for a residential compartment fire involving exposed mass timber structures. The fire and suppression models were first validated against experimental data obtained from the NRC fire tests that were conducted under the same project. Seventeen simulations were conducted using Fire Dynamic Simulator (FDS) software. The following parameters were investigated: effect of fuel arrangement and location on fire severity in exposed wood compartment, effect of different finishing on fire severity in compartment, fire and suppression in open space vs compartment, effectiveness of water mist systems in fire suppression in compartments with different finishing. The results show the effectiveness of the water mist system in suppressing the fire in exposed wood compartments where a high heat release is expected due to the high fuel load"--Executive summary, page iv.
A major concern with tall wood buildings is fire during or after an earthquake. Through a survey of factors including reliability of systems, reliability of water supplies, availability of professional and civilian fire fighting, the paper will examine the overall reliability of sprinkler systems in including assessment of the ability untrained fire fighters to suppress fires in a timber high-rise in the absence of professional fire fighters. A probability based fault tree analysis will provide guidance designers of tall wood buildings in providing acceptable fire safety after a seismic event.
The intent of this project is to research evaluation and rehabilitation methods that are applicable to mass timber structures following a fire. This includes addressing both fire damage and water damage from sprinkler activation and/or the use of firefighting hoses. This report provides an overview of the type of damage that might be expected following a fire and methods that might reduce potential damage (including design elements and firefighting tactics). Current and existing rehabilitation methods for wood construction will be reviewed and their applicability to mass timber structures will be discussed. This includes the ability to conduct condition assessments and repairs on building elements that can be done in place. The overall objective is to reduce uncertainty related to mass timber construction, which ultimately would allow for more accurate risk evaluation by insurance companies.
Recently, Vancouver architect, Michael Green, issued a report entitled Tall Wood, arguing that skyscrapers and other tall buildings should use more wood as a primary construction material. His argument is that wood is up to the task, is less polluting, and is more environmentally sustainable than the materials currently used. Green’s (2012) buildings would employ “massive timber” elements such as cross laminated timber, laminated strand lumber, and laminated veneer lumber. Green is not suggesting that these tall building be of wood only. Rather, he is arguing that mass timber be integrated with other commonly-used structural materials such as concrete and steel.
While wood and wood-mix skyscrapers capture the imagination, extending the height of buildings with the more typical lighter-frame construction is perhaps a more practical concern. Currently, light frame construction tends to be limited to buildings of four storeys and less in North America. In some jurisdictions, this limit is mandated by building codes: in others, it is simply practice. Yet, the ability to construct acceptably safe timber structures with appropriate sprinkler and other technologies led Switzerland to change its fire codes in 2005 and allow the use of structural timber in medium-rise residential buildings of up to six storeys (Frangi and Fontana, 2010). Depending upon the application, mid-sized wood frame buildings can be a less expensive and more flexible alternative to other structures.
Despite the prevalence of wood frame structures throughout North America and parts of Europe, major concerns remain over the fire safety of such structures. This paper discusses some of the issues relating to wood structures and flammability.
"As an alternative option to conventional sprinkler system, water mist systems are considered for the protection of timber buildings because they use much less amounts of water compared to sprinkler systems. The effectiveness of high pressure water mist (HPWM) and low pressure water mist (LPWM) systems was investigated in comparison to sprinkler systems for a residential fire scenario involving mass timber structures. The most distinct characteristic of the HPWM and LPWM systems was fine water droplets generated from the nozzles, which demonstrated effective smoke cooling in the room. Although the water spray rate of the HPWM was four times lower than that of the sprinkler system, the water mist systems effectively control the fire and maintained the room tenable. Most systems (HPWM, LPWM and sprinklers) tested in this study did not prevent fire damage on the CLT walls, but the HPWM system with a wide spray angle demonstrated rapid fire suppression and protection of the CLT walls. In all tests, a large water pool formed on the floor, which appeared proportional to the total water spray discharge in each test, and the moisture contents measured on the surface and bottom edges of the CLT panels indicated that water can penetrate into the interface between the floor and the wall in a typical CLT assembly"--Executive summary, page 1.
