I Want to Use Steel Trusses and Glulam Columns
Reader TOM in KNOXVILLE writes:
“I am planning on using steel 50ft trusses. All the kits I found recommend 6×6 or 8×8 but I wanted to use glulam columns. Do you know if or why they wouldn’t be recommended. 3 ply 2×8 was my plan but haven’t found a single person that’s done it. Thanks!”
Your desire to utilize glulam columns is admirable. You will find them to be straighter, stronger, lighter weight and much better treated than solid sawn columns.
Why you are not seeing them with steel truss kits?
In a word – PRICE
Most often steel truss post frame kits are being sold as ‘roof only’ structures – in order to drive prices down. I have seen some great prices advertised, however as prices get lower, so does usually quality and or service. Things tend to be not included, such as trims and condensation controls. Most of these buildings are not engineered, other than maybe trusses. However, even your best steel truss engineering is negated if quality controls are not present at wherever they are being manufactured. Use of steel of a lesser grade or thickness than specified can compromise strength. Pre-manufactured trusses are supposed to have in plant quality control and random quarterly third-party inspections, having spoken with a few of these (in hopes to find a reliable provider of steel trusses) – none of them appear to be aware of this requirement. Steel trusses should also be fabricated by certified welders. While I am sure there are some great steel truss providers, they are seemingly difficult to find.
Back to your column question….as most of these kits are sold as roof only, they end up with long portions of columns unsupported by bracing or walls. From ground to truss. Members in compression (columns) will tend to buckle in their least direction, when unsupported. A three ply glulam column has a least dimension of 4-1/8 inches, so while it is far superior in bending strength, it is prone to buckle at a significantly lesser length than a 6×6 (least dimension being 5-1/2 inches). Glulam columns are going to be more expensive than solid sawn columns, but when their ability to carry a wind load is factored in, they become a relative bargain.
If you are a social media person, you may have seen a few pictures of steel truss failures recently. Most steel trusses are not engineered to carry snow loads.
My recommendation would be to use wood trusses. If you are trying to gain interior clear height, wood trusses can closely mimic what steel will do. Wood trusses are far easier to finish overhangs and if you want to have a ceiling finished at bottom chord height, wood trusses make it very easy to achieve. Wood trusses are subject to extremely stringent quality control standards. Every set of trusses we manufacture has to have extensive records kept to verify accuracy of members and connectors, plus – we have third party inspections.
