Knowledge Base: Member Size

Cross Section – Truss beam size is dependent upon the appearance desired and structural considerations. Either factor may override the other. Every truss must be of adequate size to support itself. Additional beam cross section may be required to support roof loads. We commonly fabricate trusses with members from 2” to 12” thick and 4” to 24” wide. Members of 2-inch thickness are typically used in Multi-ply trusses. Most single-ply trusses start with a minimum size of 4” x 6” section and increase in size from there. Strength may be increased by adding either thickness or width, but adjustments to the latter dimension add more strength per unit increase.

Length – Continuous length solid timbers are limited by sizes stocked at timber mills, which is determined by available tree size. Larger section timbers are more difficult to obtain in longer lengths. Timbers in most species can be obtained up to 40 feet in length. If solid timbers are desired for spans greater than 40’, splices can be engineered in most trusses. Much larger beam lengths can be achieved using Glulam material.