3.1.6.15.Combustible Elements in Partitions

(1) Solid lumber partitions not less than 38 mm thick and partitions containing wood framing that do not conform to Article 3.1.6.3. are permitted in a building or part of a building permitted to be of encapsulated mass timber construction, provided the partitions are (a) protected on each face with not less than (i) a single layer of 12.7 mm thick Type X gypsum board, with all joints either backed or taped and filled, conforming to ASTM C1396 / C1396M, “Standard Specification for Gypsum Board,” or CAN/CSA-A82.27- M, “Gypsum Board,” (ii) a single layer of 19 mm thick fire-retardant-treated wood, on solid lumber partitions, or (iii) a single layer of 19 mm thick fire-retardant-treated wood, on partitions containing wood framing, with wood stud cavities filled with noncombustible insulation, and (b) not installed as enclosures for exits or vertical service spaces.