Wednesday, March 26, 2025
Mass Timber: Advanced Topics
Rooms C123–124Presentations in this session include:
- From Historical Precedents to Modern Challenges of Mass Timber Connections
- Why WOODEN You? Efficient Timber to Timber Connection Detailing
- Fire Design Considerations for Type IVB Mass Timber
- Testing Without Standards: Seismic Deformation Compatibility of Mass Timber Gravity Connections
- Service Conditions and Durable Design for Fasteners in Mass Timber Construction
- Screw Failures in Mass Timber Construction: The Role of Hydrogen Embrittlement
Moderator:

Scott Breneman
WoodWorks - Wood Products Council
From Historical Precedents to Modern Challenges of Mass Timber Connections
This course provides a comprehensive overview of mass timber connection design, encompassing historical context, practical fabrication considerations, durability concerns, and seismic performance requirements. Participants will explore the evolution of timber joinery, drawing inspiration from historical precedents in the Pacific Northwest and examining how these techniques inform modern mass timber construction. The session will delve into efficient fabrication strategies, focusing on optimizing connection detailing for cost-effectiveness and ease of installation, while also addressing critical aspects of fire design for Type IVB construction, including code interpretation and AHJ interaction.
Furthermore, the course will address the long-term performance and durability of mass timber connections, with a focus on fastener selection and behavior under various service conditions. Attendees will gain insights into the detrimental effects of moisture, corrosion, and hydrogen embrittlement on fastener integrity, along with mitigation strategies and best practices. Finally, the session will address the critical issue of seismic performance, examining the challenges of ensuring deformation compatibility in gravity connections and discussing current testing methodologies and the need for standardized industry criteria.

Why WOODEN You? Efficient Timber to Timber Connection Detailing
For over 1000 years, wood to wood joinery has successfully kept timber buildings strong and standing. In many situations, mass timber connections can be greatly simplified for both fabrication and installation, resulting in reduced complexity, lower cost, and easy installation.
Supply price is not simply based on material quantities. Fabrication times and complexities can greatly impact the cost of a glulam portion of mass timber project. To get even more granular, not all tools on a CNC robot are created equal in terms of speed of fabrication. As a fabricator, we have seen all scales of complexity come across our desk and have developed preferences and limitations to use the most efficient tooling to get the job done.
Efficient and effective timber to timber connections will be highlighted with a brief description of structural analysis considerations. Joinery tolerances will be discussed with an aim to achieve clean aesthetic goals as well as ease of installation. We’ll highlight special considerations to respect the unique anisotropic properties of mass timber as well as field fit tolerances. Tips and things to ask for from your fabricator to ensure accuracy of member and connector placement in the field will be presented.

Fire Design Considerations for Type IVB Mass Timber
The use of Type IVB construction is an enticing option for high-rise projects, given the favorable carbon footprint when compared to other construction materials, and the ability to expose a significant amount of the structure. With 2-hour ratings required at all primary structural elements, special attention must be paid to detailing at connections to ensure that both aesthetic goals and fire rating requirements are met. While off the shelf connections and fireproofing products are becoming more and more available on the market, applicability to specific conditions of each project must be considered when interfacing with the AHJ.
This presentation discusses detailing lessons learned from Julia West House — a type IVB housing project currently under construction in the city of Portland, Oregon. Topics include the relationship of steel components, wood, and non-combustible cover; how to use existing testing; where engineering judgements can be utilized; and bringing on a fire protection engineer to support strategies.
Interpretation of newly adopted building codes is also an important consideration when bringing first-of-their-kind tall mass timber projects through permit, so this presentation also outlines recommended strategies for interfacing with the AHJ to keep projects on schedule through permitting.

Testing Without Standards: Seismic Deformation Compatibility of Mass Timber Gravity Connections
An important performance characteristic of mass timber connections is seismic deformation compatibility. ASCE-7 requires structures in Seismic Design Category D thru F to have their gravity connections be adequate for the combined effects of gravity load and seismic forces resulting from displacement due to the design story drift. However, there are no standards to guide the testing requirements to demonstrate adequate connection performance. Testing is needed to allow specifiers to use pre-engineered connectors to improve the efficiency of mass timber construction. The presenter will highlight the seismic deformation compatibility testing of concealed beam hangers performed by Simpson Strong-Tie to provide background on current testing approaches and acceptance criteria that have been utilized. The presenter will summarize current methods for testing to inform the audience on the suitability of standardized pre-engineered connections. There will also be recommendations and questions for the audience to consider, as the presenter advocates for the industry to develop standard criteria for seismic deformation compatibility of mass timber connections.

Service Conditions and Durable Design for Fasteners in Mass Timber Construction
This presentation explores how service conditions critically impact the performance and durability of fasteners in mass timber construction. Fasteners are a key component in the integrity and lifespan of structures, especially when exposed to varying environmental factors such as moisture, pollution, and corrosive marine environments.
Attendees will gain insights into the different service environments—dry, wet, and waterfront — and their direct effects on fastener connections. The discussion will cover the impact of moisture content on fastener performance, highlighting moisture content adjustment factors both at fabrication and in service. Additionally, we will examine heightened corrosion risks, particularly in chemically treated wood, and explore advanced mitigation strategies, including metal compatibility and protective coatings.
A significant focus will be on hydrogen embrittlement and bimetallic contact corrosion, addressing guidelines for preventing these conditions. Practical design considerations will also be shared, emphasizing fastener spacing, installation techniques, and accommodating wood movement.
The presentation will be grounded in real-world case studies, offering lessons learned from successful mass timber projects. Engineers, architects, and construction professionals will walk away equipped with knowledge to ensure fastener durability in diverse service conditions, advancing the resilience of mass timber construction.

Screw Failures in Mass Timber Construction: The Role of Hydrogen Embrittlement
The reuse of construction elements is gaining importance in promoting sustainability. This includes the potential for reusing wood screws, with one possible application being lifting and transport systems. This study seeks to evaluate whether screws, typically designed for single use, can be safely reused in these specific contexts.
By combining a literature review with experimental testing, this presentation will assess the mechanical integrity of screws after repeated cycles of use. The results will guide the development of tools to determine screw reusability and may contribute to future updates in standards. While this study focuses on lifting and transport, the findings could open doors to future exploration of screw reuse in broader construction applications, advancing circularity in the industry.
