A method of forming a hollow composite construction member of the type suitable for use as building material includes providing an elongated inflatable mold assembly having a longitudinal axis, a flexible tubular bladder wall defining an elongated inflatable cavity, a reinforcing fabric positioned concentrically around the flexible bladder wall, and a flexible air-impervious outer layer positioned concentrically around the fabric. The bladder wall and the outer layer define an elongated annular space with the fabric positioned therein. Tension is applied longitudinally to the fabric and fluid is introduced into the cavity to at least partially inflate the mold and shape the fabric. The mold is shaped to a desired shape while maintaining the fabric under tension. The elongated annular space and the fabric are infused with a rigidification material. The rigidification material is hardened while maintaining the fabric in tension to form a rigid hollow composite construction member.