A Truss Designer’s Opinion on Bracing – Part I
Sometime last week Christopher Gould, President of Gould Design, Inc. (GDI), asked the design team to give our thoughts on truss bracing and how much we worry about it when designing. At first I said “Um, I don’t really have any. I was never really taught to watch for it or to really care about it until I came to GDI.” The training I received taught me otherwise.
I previously knew that three bracing blocks on any one given web wasn’t a good thing. I also knew two web braces wasn’t ideal either. Without prior knowledge of easier ways to get rid of them other than upgrading lumber, there wasn’t much one could do. I took some time to think about bracing and why we are taught tricks to help eliminate them for our clients.
Here are 5 reasons I came up with after some consideration:
- Eliminating bracing first and foremost helps the framers out a lot. It’s one less thing they have to worry about and apply to the trusses. With houses getting bigger and more complex, it would save a lot of time, money, and material if we, as designers, took a couple extra minutes to flip some webs or upgrade lumber before they are even built.
- Reducing the amount of bracing also lowers the overall material cost on the project.
- Another reason I think getting rid of bracing is beneficial would be for repairs. A truss would be a lot easier to repair if the webs in it were sturdy enough or flipped the right way to handle the compression and tension from the forces being put on the truss. What could have been a 2 or 3′ pre fab scab is now a 5 or 6′ scab because the web behind what needs to be cut or modified now won’t work. I am not saying this should ever happen, but I have seen it.
- Preventing buckling and collapse is also a big issue. There is this amazing document called the BCSI (Building Component Safety Information) put out by the SBCA (Structural Building Components Association) that educates carpenters how to properly brace. It informs them that there are 2 types of bracing: Temporary AND Permanent. But do they use it? Have they been educated?
- The biggest reason has to be proper installation and erection of the truss system. There have been human casualties from improper bracing on jobsites. Without bracing, the truss system fails. Learn why by watching this short video here.
In today’s world, as I would imagine as it has always been, people want things done the most efficient and productive way that can be done. With massive amounts of bracing, it kind of takes that idea, chews it up and spits it back out all the while laughing about it. With big hip roofs, your almost left with bracing each and every truss separately as anything is seldom the same. It makes it really tough to run CLB bracing (Continuous Lateral Bracing) when each truss web pattern is unique. To use CLB, there needs to be 3 trusses with matching web configurations for it to be effective.
Almost every truss drawing you will see; the designer has left the CLB on as the “default” when engineering the truss, rather than taking the time to engineer each truss web brace properly. Then the engineer seals the drawing, assuming that the people erecting the trusses will use the BCSI material properly. When CLB is not an option, then it is up to the carpenter (someone who knows very little about trusses) to decide how to properly brace. We are HOPING that the building inspector will at least be able to identify this if the carpenter is in error. How can this be? Why are we allowing this to happen in the industry?
So let’s say that CLB is ruled out. Then you’re left with “Scab”, “T”, “L”, or “U” bracing options. Or if the builder/carpenter is really on his game, you can have bracing plated right on to the truss webs. These bracing techniques are exactly how they sound. A “Scab” is a piece attached to the web. The catch is it needs to be the same length & grade as the web itself. A “T” brace creates a “T” with the Web in question. An “L” brace creates an “L”. The “U” brace, which I think should be avoided at all costs, creates a “U” by using a 2×4 on both sides of the web. Even with those you are left to going back to the truss sheets to figure out how long the brace needs to be. Talk about a serious time waster on a jobsite!
In conclusion, my opinion on bracing is simply this; I think we as designers should do everything within reason to eliminate as much of it as we can. Just put yourself in the shoes of the framer or inspector, would you want to add those braces to 10, 20, even 50 or 60 trusses? I know I wouldn’t. It only takes a few seconds to bump a web grade/size or flip a web. Therefore, my job is to do it right the first time and save a life from yet another collapse due to lack of knowledge, shoddy work or poor inspection process. Sure it takes a little more time, but isn’t that our job?
Stay tuned for Part 2 of this series.
Zach Failing – Design Professional
Gould Design, Inc.