Investigation of Commercial Steel Roof System Failure

Level Engineering was asked to inspect a commercial building’s roof system that was partially blown off by the high winds of the Colorado Front Range. The commercial building was under construction, but closed-in at the time of the wind storm. The building sits at the top of an escarpment with a significant elevation increase.

Upon visiting the site, our engineers initially suspected that the escarpment was not taken into consideration when calculating the wind load on the building. Accounting for the escarpment in the Topographic Factor of the wind load equation, it directly increased the wind load by 35%; meaning that the wind would have a higher impact on the building than if situated on flat land. 

ASCE 7, 2010 (Chapter 26, pg. 299)

Additionally, it appeared that the load input shown in the metal building fabricator’s drawings considered the entire footprint of the building as an “enclosed building”, which would not have taken into account the increased uplift pressures that would be seen for the overhang.

So, why did the roof come off?

During the engineer’s calculations, they found an uplift pressure of 100 pounds per square foot (psf), but the roof paneling used, was only adequate for an uplift pressure of approximately 33 psf. After discussing with the roofing panel manufacturer, it was determined that the panel used is not recommended for high wind conditions like those found on the Colorado Front Range. 

The roof paneling was subject to this extreme uplift because of an architectural design omission. Had a soffit been in place, the soffit would have taken the uplift force while the overhang roof paneling would have been subject to a reduced suction load.

Level Engineering can provide Forensic Inspections for many different commercial buildings, whether for investments, safety concerns, or natural disasters. 

Give us a call at (720) 408-0119, and our client relations team will work with you to set up a time for an engineer to come out to assess your property. 

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