he fire-resistive designs and UL-certified materials for walls and partitions are investigated to UL 263, which addresses fire-resistive requirements only. The scope of UL 263 does not address whether a wall or partition is used on the interior or exterior of a building.
UL 263 addresses the testing of wall assemblies that are asymmetrical by describing the differing components on each side of the studs to accommodate the interior and exterior of the building. These walls and partitions are typically evaluated in a manner where the interior face of the assembly is exposed to the fire, unless otherwise specified in the individual designs. For asymmetrical walls that have been evaluated where the exterior face of the assembly is exposed to fire, UL designs will state “Rating Exposed to Fire on Exterior Face”, “Rating Exposed to Fire on Either Face” or equivalent wording. In these cases, the design also identifies the construction items, such as facing, veneers or cladding required to achieve that fire resistance rating.
The ratings for symmetrical walls apply when either face of the assembly is exposed to the fire. Exterior cladding and other local code required materials may be added to symmetrical wall designs with gypsum panels attached to either wood studs or steel studs for use in exterior wall applications, provided the additional materials do not jeopardize the existing rating, as determined by the Authority Having Jurisdiction.
Where symmetrical or asymmetrical walls are used on the exterior of a building, additional requirements applicable to exterior walls, such as those regulating insulation, exterior cladding and weather protection should apply. The Authority Having Jurisdiction should be consulted to ensure compliance with these other code requirements applicable to exterior walls.