The objective of this research is to address a knowledge gap related to fire performance of midply shear walls. Testing has already been done to establish the structural performance of these assemblies. To ensure their safe implementation and their broad acceptance, this project will establish fire resistance ratings for midply shear walls. Fire tests will provide information for the development of design considerations for midply shear walls and confirm that they can achieve at least 1-hour fire-resistance ratings that are required for use in mid-rise buildings.
This research will support greater adoption of mid-rise residential and non-residential wood-frame construction and improve competition with similar buildings of noncombustible construction. This work will also support the development of the APA system report for midply walls, which will be a design guideline for using midply walls in North America.
Changes to the 2021 International Building Code (IBC) have created opportunities for wood buildings that are much larger and taller than prescriptively allowed in past versions of the code. Occupant safety, and the need to ensure fire performance in particular, was a fundamental consideration as the changes were developed and approved. The result is three new construction types—Type IV-A, IV-B and IV-C—which are based on the previous Heavy Timber construction type (renamed Type IV-HT), but with additional fire protection requirements.
One of the main ways to demonstrate that a building will meet the required level of passive fire protection, regardless of structural materials, is through hourly fire-resistance ratings (FRRs) of its elements and assemblies. The IBC defines an FRR as the period of time a building element, component or assembly maintains the ability to confine a fire, continues to perform a given structural function, or both, as determined by the tests, or the methods based on tests, prescribed in Section 703.
FRRs for the new construction types are similar to those required for Type I construction, which is primarily steel and concrete. They are found in IBC Table 601, which includes FRR requirements for all construction types and building elements; however, other code sections should be checked for overriding provisions (e.g., occupancy separation, shaft enclosures, etc.) that may alter the requirement.
Project contact is Rokib Hassan at the National Research Council of Canada
Summary
Phase two of a four-phased research project, with the overarching goal of developing transparent intumescent coating (TIC) for mass timber construction, which would be technology certified, IP protected and licensed out. The use of TIC would ensure that fire resistance rating requirements are met while reducing the need for encapsulation, resulting in increased overall aesthetics provided by timber. Phase two focuses on demonstrating a proof-of-concept on a small scale and optimizing the TIC formula and coating thickness based on the testing results. Small scale tests will be conducted to measure fire resistance, weatherability and fire toxicity.
This guide provides the directives needed for designers of tall wood buildings to produce their designs, plans and specifications. It has been developed to give them the information and general concepts required, based on the selected system. The elements and details required to comply with the guidelines in this document must be incorporated from a project’s initial design phase.
Part 1 – Guidelines contains several sections, including one that deals with basic conditions and describes the minimum general conditions applicable to any project for the construction of a wood building exceeding 6 storeys. The following sections contain special provisions that specify and complete the basic conditions.
For many years, exposed heavy timber framing elements have been permitted in U.S. buildings due to their inherent fire-resistance properties. The predictability of wood’s char rate has been well-established for decades and has long been recognized in building codes and standards. Today, one of the exciting trends in building design is the growing use of mass timber—i.e., large solid wood panel products such as cross-laminated timber (CLT) and nail-laminated timber (NLT)—for floor, wall and roof construction. Like heavy timber, mass timber products have inherent fire resistance that allows them to be left exposed and still achieve a fire-resistance rating. Because of their strength and dimensional stability, these products also offer an alternative to steel, concrete, and masonry for many applications, but have a much lighter carbon footprint. It is this combination of exposed structure and strength that developers and designers across the country are leveraging to create innovative designs with a warm yet modern aesthetic, often for projects that go beyond traditional norms.
This paper has been written to support architects and engineers exploring the use of mass timber for commercial and multi-family construction. It focuses on how to meet fire-resistance requirements in the International Building Code (IBC), including calculation and testing-based methods. Unless otherwise noted, references refer to the 2018 IBC.
Fire Performance Requirements of Non-Load-Bearing Wood-Frame In-Fill Walls in Concrete/Steel Hybrid Buildings. Part 1 - Literature Review of International Building Code
Related sections in the International Building Code (IBC) were reviewed regarding use of wood components in non-combustible buildings, and light-frame wood buildings or heavy timber buildings greater than 4-storeys in height.
The highlights of this review are:
a) Fire-retardant-treated (FRT) wood can be used in partitions when the required fire-resistance rating is not more than 2 hours. This includes all types and occupancy groups of Types I and II construction;
b) FRT wood can be used in non-bearing exterior walls in Type I, II, III and IV construction;
c) Wood components can be used in interior walls for Type III and IV construction;
d) Wood components can be used in both interior and exterior walls for Type V construction.
When a sprinkler system is installed according to NFPA 13 [1], it is possible to build a light-frame wood building or heavy timber building over 4-storeys according to the following provisions:
a) Type IIIA 6-storey light-frame wood buildings using FRT wood for exterior walls for Occupancy group B (Business), H-4, and 5-storey light-frame wood buildings for Occupancy group F-2, H-3, I-1(Institutional), R (Residential), S-2;
b) Type IIIB 5-storey light-frame wood buildings using FRT wood for exterior walls for Occupancy group R;
c) Type IV (HT) 6-storeys timber buildings for Occupancy group B, F-2, H-4 and S-2;
d) Type IV (HT) 5-storeys timber buildings for Occupancy group F-1, H-3, I-1, R, S-1 and U.
The 2021 International Building Code (IBC) introduced three new construction types—Type IV-A, IV-B and IV-C—which allow tall mass timber buildings. For details on the new types and their requirements, see the WoodWorks paper, Tall Wood Buildings in the 2021 IBC – Up to 18 Stories of Mass Timber. This paper builds on that document with an in-depth look at the requirements for shaft walls, including when and where wood can be used.
The Softwood Lumber Board, Arup, MyTiCon and DR Johnson have partnered to complete three full-scale fire tests for glulam beam to column connectors. The fire tests have been completed for “off-the-shelf” connectors for glulam beams, testing the connector to meet a minimum of a 1hr fire resistance rating (FRR).
To assist the construction industry, three different configurations of glulam beam to column connections were fire tested at an approved fire testing facility. The fire tests were carried out to meet ASTM E119-16a “Standard Test Methods for Fire Tests of Building Construction and Materials”, hence meeting Chapter 7 of the IBC.
The completed fire tests and supporting reports allow engineers and architects to specify these tested connection assemblies and satisfy the requirements of the IBC. Approval by an authority having jurisdiction (AHJ) will therefore be easier for future building projects.
In January 2019, the International Code Council (ICC) approved a set of proposals to allow tall wood buildings as part of the 2021 International Building Code (IBC). Based on these proposals, the 2021 IBC will include three new construction types—Type IV-A, IV-B and IV-C—allowing the use of mass timber or noncombustible materials. These new types are based on the previous Heavy Timber construction type (renamed Type IV-HT) but with additional fire-resistance ratings and levels of required noncombustible protection. The code will include provisions for up to 18 stories of Type IV-A construction for Business and Residential Occupancies.
Based on information first published in the Structural Engineers Association of California (SEAOC) 2018 Conference Proceedings, this paper summarizes the background to these proposals, technical research that supported their adoption, and resulting changes to the IBC and product-specific standards.
