Disadvantages
Due to the high cost of labor, use of this type of beam has greatly declined. The advent of high-strength engineered lumber which uses modern adhesives and lower cost wood fibers has rendered this system largely obsolete. For example compare the capacity of 2 beams spanning 18 feet: the allowable strength of a 3½ʺ × 11¼ʺ laminated veneer member has a tabulated allowable applied load of 398 plf (pounds a linear foot); compare this to a 2 × 12 flitch beam constructed of ½ʺ steel plate with two laminations of #2 SPF with an allowable applied load of 386 plf
The engineered lumber is cut to length and installed similar to sawn lumber; the flitch requires shop fabrication and/or field bolting. This coupled with a much increased self weight of the beam (11.4 lbs for engineered wood vs. 25.2 lbs for flitch) decreases the viability of the system.
Read more about this topic: Flitch Beam