Built-Up Column Stability in Wood Construction

Abstract

Wood construction is common for low-rise buildings, including residential and light commercial structures. For these types of structures, vertical structural members may consist of multiple wood studs, called built-up columns. As wood-framing becomes increasingly common for multi-story structures, concerns of both structural strength and stability of the wood members should be of paramount importance to the engineer. Specifically, the engineer must have knowledge of the type and extent of bracing present to properly determine the capacity of each member. Most commonly, wood studs in low-rise buildings are braced in the weak direction by fastening wall sheathing to the face of the stud of the narrower dimension. The use of gypsum board wall finishes to brace wood stud walls (and for lateral shearwall diaphragms) has become common in the design of wood structures. However, engineers must remain aware of the limitations of gypsum board when designing heavily loaded, non-repetitive members such as columns. These limitations are particularly important for the design and detailing of built-up columns. Design and construction defects related to wood columns in a wood-framed townhome project are presented herein. The subject three-story structures utilized built-up wood columns that depended on gypsum board for stability bracing. The columns did not satisfy the National Design Specification requirements for built-up columns. The proper design of the columns and the implications of using gypsum board for bracing will be discussed.