Project contact is Kuma Sumathipala at the American Wood Council
Summary
The United States has a vast supply of forest biomass, which provides an abundant resource suitable for the manufacturing of mass timber products. Recent research has shown that these mass timber products can be safely implemented in tall buildings. In 2018 and 2019, this research led to changes allowing the construction of 18 story buildings with mass timber structures in the 2021 International Building Code (IBC). Although this development has created opportunities, it does not respond to recent architectural trends, as the new regulations do not allow for visible mass timber in buildings exceeding 12 stories in height and only allow for limited areas of visible Cross Laminated Timber (CLT) surface in buildings from 9 to 12 stories in height.
The strict limitation on the area of visible mass timber in 2021 IBC was based partially on fire performance of CLT manufactured to an earlier edition (2012) of ANSI/APA PRG 320. New adhesive qualification requirements in the 2018 standard have significantly improved the fire performance of CLT. This improved fire performance represents an opportunity to justify increases to code-prescribed limits on exposed mass timber areas which would respond to current, and likely future, architectural aesthetic demands, allowing for an expansion of the market for tall mass timber buildings.
In order to justify these increases in allowable exposed mass timber areas, compartment fire tests will be designed and performed to demonstrate that the fire performance of increased exposed mass timber surfaces are consistent with the (newly-recognized) International Building Code safety criterion. In addition, fire safe solutions for the intersections between exposed mass timber members and restoration of fire-damaged exposed mass timber are needed to be developed and tested. Test results and other findings will be used to develop and justify new requirements for U.S. model building codes, thereby enabling more innovative utilization of renewable U.S. forest resources in construction.
The acceptable solutions in Division B of the anticipated 2020 NBCC limit the height of Groups C and D buildings of sprinklered encapsulated mass timber construction (EMTC) to 12 storeys in building height, and a measured building height of 42m. The recently published 2021 IBC contains provisions to permit buildings of mass timber construction under the IBC Type IV construction, surpassing the NBCC provisions by maximum building height, building area, occupancy groups, and interior exposed timber. The IBC mass timber buildings are permitted to have a building height of maximum 18 storeys, depending on the occupancy group. Within Type IV construction, four subdivisions are described to have varying maximum permissible building height, area, fire resistance rating (FRR), and interior exposed timber.
Through a comparison of mass timber provisions of both Codes, relevant research reports, test reports, industry standards, this report documents the consequential and inconsequential differences and developed conclusions on whether the NBCC can adopt the IBC provisions, and with what modifications so that the new provisions may fit the NBCC context.
Project contact is Jianhui Zhou at the University of Northern British Columbia
Summary
The impact sound perceived in the lower volume in a building is radiated by the vibration of the ceiling transmitted from the vibration of the floor generated by an impact source in the upper volume. Thus, the dynamic behaviour of a floor is one crucial intermediate step to understand the impact sound insulation performance of such a floor. A key to reducing the impact sound is to isolate the structural floor from the subfloor. Floating floor construction is a common way of improving the impact sound insulation, which is to float a concrete topping on the mass timber floor with an elastic layer in between. There are two types of floating floor solutions, a) with a continuous elastic layer and b) with point bearing elastic mounts as shown in Figure 1. This study will investigate both solutions and will provide guidance on how to adopt both solutions for mass timber floors with an exposed ceiling.
The objectives of this project are:
1. To measure the sound insulation performance of mass timber floors with full-scale concrete topping on various continuous elastic interlayer materials
2. To measure the sound insulation performance of mass timber floors with full-scale concrete topping on discrete elastic load mounts
