Building Enclosure Design of Exterior Soffits

October 21, 2019
Publication: Building Design & Construction
Author(s): John Sekel John Karras

Commercial building designs have long incorporated exterior soffits, better known outside of the building design and construction industry as the underside of any projecting building feature. Aside from soffits at the eave or rake edges of a steep-slope roof, the soffits that are the focus of this article are located on the underside of a steel- or concrete-frame projecting building level or on the underside of other horizontal projections, such as balconies and canopies. 

Traditionally, soffit designs provided an exterior ceiling material simply to conceal unsightly structural features. But when an exterior soffit connects the façades of consecutive building levels, it composes part of the building enclosure and, accordingly, requires performance-based design attention.

With current code requirements, increasingly complex façade articulations, and the abundance of contemporary materials incorporated into architectural façade designs, this is not always a straightforward task. The alternative — treating an exterior soffit as merely a surface on which to hang cladding materials — can render the building enclosure vulnerable to performance problems. Soffit design strategies intended to avoid water penetration, air infiltration, condensation, and premature material deterioration are highlighted in this course.