Cross-Laminated Timber Gets 2-hour Wall Rating

A press release from the American Wood Council reports that the results of successful fire tests allowed for CLT panels to be added to the 2015 IBC as an exterior 2-hour rated wall assembly for Heavy Timber (Type IV) buildings.  According to the adopted code language, the exterior side of the panel must be covered with gypsum board or fire retardant treated wood sheathing or a non-combustible material.  From the AWC:

Prior to the [IBC] hearings, as part of a project to produce a U.S. design manual for cross-laminated timber (CLT), AWC conducted a successful ASTM E119 fire endurance test on a CLT wall at NGC Testing Services in Buffalo, N.Y. The wall, a 5-ply CLT specimen (approximately 7 inches thick), was covered on each side with a single layer of 5/8" Type X gypsum wallboard. The wall was loaded to the maximum attainable by the test equipment, although it remained significantly below the full design strength of the CLT. It was then exposed to a standard fire that reached over 1800 degrees Fahrenheit in the first 90 minutes of exposure.

"While only seeking a 2-hour rating as required by building code provisions, the test specimen lasted 3 hours 6 minutes. This may also open up additional possibilities in a few specialized locations where a 3-hr fire resistance rating might be required," said AWC Vice President of Engineering Brad Douglas. 

Cross-Laminated Timber is a robust framing solution that has been developed in Europe for the past decade mainly because of its lower carbon footprint than comparable framing systems of steel and concrete.  The technology has recently expanded to North America and has gained some notoriety in British Columbia.