Neutral Publishes 3h Mass Timber Fire Test Results

August 18, 2025

MADISON, WI — Neutral publishes the results of a first-of-its-kind successful 3 hour fire test for a hybrid mass timber building assembly with standard connectors for free use by industry practitioners. 

‍

Neutral is a real estate development company focused on creating sustainable and healthy mixed-use communities based in Madison, WI and San Jose, CA. Neutral is implementing mass timber as a sustainable alternative to conventional construction methods.

‍

Neutral 1005 N Edison St in Milwaukee, WI is a record setting project. It’s slated to become the tallest composite mass timber building in the United States. The structure would include cross-laminated timber floor decks manufactured by Stora Enso and glulam beams and columns by WIEHAG.

‍

From the outset, the project team recognized that standardized solutions for mass timber connections would be critical—not just for this project, but for the success of future tall timber buildings across the industry.

‍

One of the major challenges the project team faced was that many standard connection configurations had never been tested under a 3-hour fire-resistance rating (FRR)—a requirement that is essential to advancing tall mass timber construction following the fire rating standards for IBC construction types I-A. Neutral set out with a clear mission: to validate that standard, concealed mass timber connections can meet this rigorous fire performance threshold.

‍

As part of the building permit variance process for the Edison project, Neutral has conducted a series of fire resistance tests utilizing mass timber glulam columns and beams, in combination with standard off-the-shelf mass timber connectors by Wiehag and Simpson Strong Tie. The goal of the test was to determine a 3 hours fire resistance rating, proving equivalent performance of the mass timber structure with IBC construction type I-A.

‍

The test has been conducted in the Spring of 2025 at SwRI lab in San Antonio, TX. It was prepared in collaboration with Forefront Structural Engineers, Arup as fire protection engineers, CDSmith as the general contractor, HPA as architect, and other industry professionals.

‍

“The first two full-scale tests focused on beam-column assemblies under design load conditions. Both the glulam beams and columns measured 20.47” x 14.19” (520 mm x 360 mm), representing typical flush-mount conditions ideal for constructability and cost optimization. We tested two off-the-shelf concealed connectors—one from Simpson Strong-Tie and one from Wiehag—designed in compliance with NDS and AWC TR-10 guidelines while extrapolating to the necessary 3 hr FRR. To accommodate fit-up tolerances and mitigate long-term shrinkage, we applied an off-the-shelf intumescent fire tape around three faces of the beam end.” - explains Josh Dortzbach of Forefront.

‍

Test results exceeded expectations: the assemblies performed exceptionally under loaded fire conditions. The intumescent fire tape significantly contributed to limiting charring and protecting the connection region, helping preserve structural integrity throughout the fire duration.

Free Access to Test Results

Neutral is publishing the test results for open use by industry researchers and practitioners around the world. This is the first successful implementation of the three-hour fire test of a mass timber assembly that illustrates the safety and the potential of mass timber application in high-rise construction.

‍

DOWNLOAD FREE REPORT (3H TEST W WIEHAG CONNECTORS)
DOWNLOAD FREE REPORT (3H TEST W SIMPSON CONNECTORS) 

‍

(The second test series targeted full-scale glulam columns subjected to axial and fire loading for 3 hours. The column tests were conducted in July and August 2025 and have successfully passed, these reports will be released at a later date).

‍

Mass timber buildings have significantly increased in number globally due to the material’s benefits in sustainability, architecture, and proven commercial drivers. However, high-rise mass timber buildings are still relatively small in number globally, and when a building is aiming to go beyond currently constructed heights, the project team must closely collaborate with the building code and fire authorities to address and solve new fire safety requirements. 

‍

The long-term success of tall mass timber projects like Neutral 1005 N Edison St hinges on more than theoretical calculations or assumed material properties—it requires empirical validation through rigorous fire testing. This initiative, jointly undertaken by Neutral, Forefront Structural Engineers, Arup, HPA, and Stora Enso is helping to set a new benchmark for the industry.

‍

“Currently, mass timber connections are often considered to be a lesser-known component for engineered timber in fire and there is still much to learn about whether these connections can be better utilized by project teams. Looking ahead, these fire resistance tests prove that mass timber can be designed to achieve the most stringent of fire resistance requirements.” - mentions David Barber of Arup

‍

As we look to build more sustainably, there is value in making fire resistance tests available so that they can be utilized by other developers and designers as part of their justification for a high-rise mass timber building. As we push toward carbon-neutral construction, advancing mass timber systems—alongside innovations in high-efficiency concrete structures, like Edison's lateral force-resisting system—will be key.

‍

“True sustainability demands deep collaboration among developers, engineers, manufacturers, contractors, and future building users. Together, we’re not just building better buildings—we’re engineering a more sustainable future.” - says Daniel Glaessl, Partner and Chief Product Officer at Neutral.

‍

‍

Team credits

‍

Learn more