Cross Laminated Timber (CLT), which is made by laminating dimension lumber at right
angles, is an innovative high-performance building material that offers many positive attributes
including renewability, high structural stability, storage of carbon during the building life, good
fire resistance, possibility of material recycling and reuse. It is conceptually a sustainable and
cost effective structural timber solution that can compete with concrete in non-residential and
multi-family mid-rise building market. Therefore, there is a need to understand and quantify the
environmental attribute of this building system in the context of North American resources,
manufacturing technology, energy constraints, building types, and construction practice. This
study is to compare energy consumption of two building designs using different materials, i.e.
CLT and concrete.
The Fire Test Laboratory of NGC Testing Services (NGCTS) conducted testing for American Wood Council (AWC) on a load-bearing, Cross-Laminated Timber (CLT) and gypsum board wall assembly to evaluate its fire resistance properties when exposed to fire acco...
European experience shows that Cross-Laminated Timber (CLT) can be competitive in mid-rise and high-rise buildings. Although this system has not been used to the same extent so far in North America, it can be viable wood structural solution for the shift towards sustainable densification of urban and suburban centers. For these reasons FPInnovations has undertaken a multi-disciplinary project on determining the performance of a typical CLT construction, including quantifying the seismic resistance and force modification factors for CLT buildings in Canada and the US.
In this report, a performance-based seismic design (PBSD) of a CLT building was conducted and the seismic response of the CLT building was compared to that of a wood-frame structure tested during the NEESWood project. A suitable force modification factors (R-factors) for CLT mid-rise buildings with different fasteners were recommended for seismic design in Canada and the US. The six-storey NEESWood Capstone building was redesigned as a CLT building using the PBSD procedure developed during the NEESWood project. The results from the quasi-static tests on CLT walls performed at FPInnovations were used as input information for modeling of the main load resisting elements of the structure, the CLT walls. Once the satisfactory design of the CLT mid-rise structure was established through PBSD, a force-based design was developed with varying R-factors and that design was compared to the PBSD result. In this way, suitable R-factors were calibrated so that they can yield equivalent seismic performance of the CLT building when designed using the traditional force-based design methods.
Based on the results of this study it is recommended that a value of Rd=2.5 and Ro=1.5 can be assigned for structures with symmetrical floor plans according to NBCC. In the US an R=4.5 can be used for symmetrical CLT structures designed according to ASCE7. These values can be assigned provided that the design values for CLT walls considered (and implemented in the material design standards) are similar to the values determined in this study using the kinematics model developed that includes the influence of the hold-downs in the CLT wall resistance. Design of the CLT building with those R-factors using the equivalent static procedures in the US and Canada will result in the CLT building having similar seismic performance to that of the tested wood-frame NEESWood building, which had only minor non-structural damage during a rare earthquake event.
The number of occupant complaints received about annoying low-frequency footstep impact sound transmission through wood floor-ceiling assemblies has been increasing in proportion with the increase in the number of multi-family wood buildings built. Little work has been conducted to develop solutions to control the low-frequency footstep impact sound transmission. There are no code provisions or sound solutions in the codes. Current construction practices are based on a trial and error approach. This two-years project was conducted to remove this barrier and to successfully expand the use of wood in the multi-family and mid- to high-rise building markets. The key objective was to build a framework for the development of thorough solutions to control low-frequency footstep sound transmission through wood floor-ceiling assemblies.
Field acoustic tests and case studies were conducted in collaboration with acoustics researchers, builders, developers, architects, design engineers and producers of wood building components.
The field study found that:
1. With proper design of the base wood-joisted floors and sound details of the ceiling:
With no topping on the floor, the floor-ceiling assembly did not provide sufficient impact sound insulation for low- to high-frequency sound components ;
Use of a 13-mm thick wood composite topping along with the ceiling did not ensure satisfactory impact sound insulation;
Even if there was the ceiling, use of a 38-mm thick concrete topping without a proper insulation layer to float the topping did not ensure satisfactory impact sound insulation ;
A topping system having a mass over 20 kg/m2 and composed of composite panels and an insulation layer with proper thickness achieved satisfactory impact sound insulation.
2. The proper design of the base wood-joisted floors was achieved by the correct combination of floor mass and stiffness. The heaviest wood-joisted floors did not necessarily ensure satisfactory impact insulation.
3. Proper sound ceiling details were found to be achieved through:
Use of two layers of gypsum board;
Use of sound absorption materials filling at least 50% of the cavity ;
Installation of resilient channels to the bottom of the joists through anchoring acoustic system resulted in improved impact sound insulation than directly attaching the resilient channels to the bottom of the joists.
A four-task research plan was developed to thoroughly address the issue of poor low-frequency footstep impact insulation of current lightweight wood floor-ceiling assemblies and to correct prejudice against wood. The tasks include: 1) fundamental work to develop code provisions; 2) expansion of FPInnovations’ material testing laboratory to include tests to characterize the acoustic properties of materials; 3) development of control strategies; and 4) implementation.
The laboratory acoustic research facility built includes a mock-up field floor-ceiling assembly with adjustable span and room height, a testing system and a building acoustic simulation software.
The preliminary study on the effects of flooring, topping and underlayment on FIIC of the mock-up of the filed floor-ceiling assembly in FPInnovations’ acoustic chamber confirmed some findings from the field study. The laboratory study found that:
A topping was necessary to ensure the satisfactory impact sound insulation;
The topping should be floated on proper underlayment;
Topping mass affects impact sound insulation of wood framed floors;
A floating flooring enhanced the impact sound insulation of wood framed floors along with the floating topping.
It is concluded that:
1. even if the studies only touched the tip of the iceberg of the footstep impact sound insulation of lightweight wood-joisted floor systems, the proposed solutions are promising but still need verification ;
2. with proper design of the base wood floor structure, the proper combination of flooring, and sound ceiling details along with proper installation, the lightweight wood floor-ceiling assembly can achieve satisfactory impact sound insulation ;
3. this study establishes a framework for thoroughly solving low-frequency footstep impact sound insulation problem in lightweight wood-joisted floor systems.
Solutions will be developed in the next phase of this study as planned and the study will be conducted under NRCan Transformative Technology program with a project dedicated to “Serviceability of next generation wood building systems”.
FPInnovations is involved in a large research project regarding CLT construction. One objective
of this research is the creation of a design methodology for calculating the fire-resistance of CLT
assemblies/construction. This methodology will foster the design of fire-safe buildings of wood
or hybrid construction. In order to establish such calculation methods, a series of experimental
tests has been undertaken. A total of eight full-scale CLT fire resistance tests have been
conducted at the NRC fire laboratory where the panels were subject to the standard ULC S101
 fire exposure. The series consisted of three wall and five floor tests. Each test was unique
using panels with a different number of plies and varying thicknesses. Some of the assemblies
were protected using CGC Sheetrock® FireCode® Core Type X gypsum board while others
were left unprotected.
Report of Testing Cross Laminated Timber Panels for Compliance with CAN/ULC-S101 Standard Methods of Fire Endurance Tests of Building Construction and Materials: Loadbearing 3-Ply CLT Wall with Attached Wood Frame Partition
Intertek Testing Services NA, Inc. (Intertek) has conducted testing for the Canadian Wood Council, on Cross-Laminated Timber Panels to evaluate their fire resistance. Testing was conducted in accordance with the applicable requirements, and following the...