Why Fire Rated?
Rationale for Fire Rated I-joists
When joists were first introduced to the Housing Industry some 50 years ago, the benefits were quickly appreciated. Physically and dimensionally they were far more consistent than solid sawn 2x10’s and 2x12’s and these superior properties allowed for longer spans. Many of the teleposts in the basements of residential housing were eliminated. It enabled designers to create far more innovative floor plans. In addition, joists were not subject to shrinking because the OSB web contains very little moisture, thereby eliminating the squeaking ,which was so common with solid sawn lumber floors.
However, it did not take long to discover one significant weakness. In the event of a fire, the OSB web would burn through in approximately 5 minutes versus about 15 minutes for a 2x10. When the web burns through, the joist is no longer capable of carrying a load. This meant that the homeowner had less time to evacuate a burning dwelling, and the first responders would not be able to safely enter a burning residence to effect a rescue.
For this reason, Firefighters have led the lobby in North America to mandate improvement in the performance of joists in the event of a fire. The U.S. Code was amended in 2012 to provide for the following, if joist are used in residential housing:
The residence must have a sprinkler system, or
The basement must be completed dry walled, or
The joists must be enhanced to perform equivalent to a 2 x 10 in the event of a fire.
In 2018, CCMC in Ottawa was directed by its board of directors to address the gap in fire performance between 2 x 10 lumber and wooden I-joists. NBC Article 188.8.131.52 exempts single family homes from fire protecting unfinished basements when 2 x 10’s are utilized. It was clearly shown that wooden I-joists are NOT equivalent to 2 x 10’s when left unprotected.
Our premium, patented FRI assembly (WEBshield panels) complies with both the US and the Canadian 2 x 10 equivalency criteria for joists installed over unfinished basements. Our innovative approach has been used in the United States for two years, and it has already proven itself. A residential home in Denver which had just been built (but was still unoccupied) caught fire, and burned completely. The Fireman on the scene reported to us that the WEBshield performed as intended, and invited us to photograph the floor to demonstrate the actual performance.