There are disclosed building enclosure assemblies consisting of gypsum-based panel members, a support means and a fire-resistant spline, for the construction of fixed or demountable, full or partial, interior or exterior walls, ceilings and floorings, which can meet code-mandated fire-rating and wind-loading requirements, and in which differently sized and shaped panel members can be articulated to one another through the cooperative assembly of the panel members with the support means and spline.