A method of manufacture of a tapered wood beam, such as an I-beam, is described. With such method an I-beam of uniform width including a web member of uniform width and a pair of first flange members attached to the opposite sides thereof, is first produced and then cut into two portions by sawing the web member of such beam along a diagonal line to form two tapered web members each attached at one side to a first flange member. The resulting I-beam portions are then assembled by releasably fastening, such as clamping, the first flange members together in back to back relationship so that the sawn edges of the tapered web members are facing outwardly and parallel to form an assembly of substantially uniform width. This assembly is then fed through an automatic I-beam manufacturing machine, which may be the same machine in which the uniform width I-beam was produced, to fasten a pair of second flange members to the sawn edges of such tapered web members resulting in the production of two interconnected I-beams of tapered width. The two tapered I-beams are separated by unclamping the first flange members from each other.