Previous research papers on this subject do not raise the issue of a systematic approach to the design of PFRP built-up members, which should consider: various basic profiles (C- and L-shaped, etcetera); different types of connection between basic profiles (battens and or lacings, connected by bolting and/or bonding, etcetera); changes in geometric characteristics (member total length, spacing of the battens, etcetera); and various types of loading. In this context, the present paper has as the main objective to develop a design equation for built-up columns made of pultruded material. The proposed design equation is based on a preliminary series of parametric analyses of columns comprised of two closely spaced C-shaped profiles.