Lumber that is glued or laminated together is tested by the manufacturer to ensure it will withstand a certain load. If you know what your load requirements are and buy a piece rated to withstand that load, then you can be sure the laminated lumber you buy is as strong as a single piece of timber. In fact, a laminated piece, especially in longer lengths, may be easier to find. Also, thick timbers are more difficult to dry properly, while laminated pieces are made from all kiln-dried material.