Under the IBC, solid CLT is considered a Type IV or “Heavy Timber” construction. As such, it is considered to provide a 1-hour fire rating for exterior walls, structural frame, floors and roofs without additional fireproofing or sprinkling because of its low char rate. Calculations must be made to confirm structural integrity after a 1-hour burn.
Because Plenum Panels™ have voids, it is considered a combustible material and requires a 1 hour or 2-hour fire rating depending on occupancy and use. The 1-hour fire rating can be archived with a layer of 5/8” gypsum and a similar layer of light weight concrete on the floor side. These materials add deadload and reduce strength available for live loads since these layers would add about 4.5 psf to the dead load. In most cases, a sprinkler system would also provide the 1 hour of fire protection.
Using Plenum PanelsTM in multi-family and commercial applications requires either layers of 1-hour fire rating on the top and bottom or sprinkling.