Extensive Review of Champlain Towers Collapse Completed

if it is too extensive. By carefully examining reinforcing steel in the Champlain Towers South evidence, NIST’s experts were able to document the type, degree and variability of its corrosion. This has provided critical information about potential degradation and strength of the overall structure at the time of collapse.

The team was able to “reverse engineer” the materials and concrete mixture used in the original construction by conducting microscopic and chemical analyses of concrete samples extracted from the evidence. This allowed team members to quantify the degree of aging and deterioration in the concrete samples. These analyses also made it possible for them to closely recreate the concrete from Champlain Towers South and use it to build large-scale replicas that are representative of critical structural members and connections from different parts of the building that were likely involved with the collapse initiation or its progression. These replicas are being tested to failure in structures laboratories at the University of Washington and the University of Minnesota. Data from these tests will be used to inform computer simulations that will play a key role in determining the probable initiation and progression of the partial collapse and its technical causes.

The recovered evidence also revealed various ways in which the building’s materials had changed or been changed over time. This included cracking and spalling (cracking or chipping) of concrete, corrosion of steel reinforcement, prior attempts to repair cracks and spalls in the concrete, the addition of new materials and finishes to the building (including concrete planters and landscaping vegetation on the pool deck), and mineral deposits indicative of water leakage through the structural elements.

The investigation team began its work with about two dozen hypotheses of how the collapse may have initiated. Team members systematically considered all the hypotheses so that they could eventually rule out the most unlikely causes and fully understand the most probable. 

“To be confident we have determined the most likely cause or causes of this terrible tragedy amongst the many possibilities, we are collecting and analyzing all the evidence we can for and against each hypothesis,” said Glenn Bell. “We are leaving no stone unturned.”

The investigation’s six project teams continue their efforts (see details below), with the goal of completing technical work in 2025. The entire investigative team has already begun drafting the investigation’s findings and recommendations. The draft report must pass through several stages of review, starting with technical review within NIST and then a review by external subject matter experts. Following these technical reviews, the report will undergo several types of policy review before a draft report is released for public review, which is planned for the spring of 2026.