News Post

Floor Beam Collapse in a Semi-Detached House

July 3, 2021

Project Manager:

Adam Lohonyai, M.Eng., P.Eng.

Technical Experts Involved:

Yasser Korany, Ph.D., P.Eng, P.E., LEED AP, PMP
Adam Lohonyai, M.Eng., P.Eng.

Incident Description

A built-up wood floor beam in a semi-detached house collapsed, causing significant damage in the unit above. Origin and Cause Inc. was retained to investigate and determine the cause of the collapse.


A detailed visual examination of the crawlspace and the affected unit was carried out. Advanced decay was identified on the collapsed beam. Three nearly identical beams were noted in the crawlspace supporting other areas of the floor above. All three of these beams were visibly sagging. A significant amount of dryer lint was also found inside the crawlspace near the collapsed beam.

Cause of Loss

Origin and Cause Inc. determined that the floor beams were significantly undersized to safely carry the code-prescribed loads from the building, contents, and occupants above. A clothes dryer near the collapsed beam had also been improperly vented and was exhausting into the crawlspace rather than to the exterior of the house. Excess moisture from the improperly vented dryer caused the affected beam to decay and eventually collapse.