A Truss Designer’s Opinion on Bracing – Part IV
As we have pointed out on previously posts (see links for part 1, 2 and 3 below), bracing is an issue to be aware of although “It is the responsibility of the building designer or an authority other than the truss designer to indicate size, location and attachments for all permanent bracing.” According to the Truss Plate Institute of Canada, nevertheless there is bracing directly related to the truss design and is the responsibility of the builder to follow those plans.
Permanent bracing includes:
- Top Chord Bracing
- Bottom Chord Bracing
- Diagonal Web Bracing
- Anchoring of Lateral Web Bracing
The one we´ll discuss is the Permanent Lateral Bracing. This bracing requirement is clearly pointed out on the truss engineered drawings.
Since the builder will be on charge of transportation, downloading, proper handling during installation, they also have to be aware in any moment of the temporary and the permanent bracing (lives of workers and occupants are on stake). Our duty as truss designers is to make the builder´s job less complex and more secure.
So how can we make this simpler for them? Easy! There is an easy to use tool in MiTek’s VersaTruss engineering program to help. Using the “reverse web” tool in engineering, we can eliminate of many of the bracing that may be required in just a few seconds. Is your framer’s satisfaction worth only a few extra seconds per truss? Of course it is!
If this tool doesn´t work in removing the braces, we still have other choices:
- Modify the web pattern
- Modify the web size
- Modify the lumber grade
- Modify the splicing location
Sometimes we can´t do anything to reduce or remove bracing (like the truss shown above) and must kept it like it is. Then we must be sure to have similar webbing aligned on the three next trusses (minimum) to provide the proper support to the bracing for CLB (Continuous Lateral Bracing). Why? Believe it or not, that’s what they will apply 9 times out of 10, even when there are not 3 or more trusses to secure to. Yes sir, they will not use the other bracing types such as:
- Scab bracing
- “T” bracing
- “I” bracing
Also the double web bracing (2 CLB’s on a single web) is something to be aware a preferably to avoid. In those cases we can use the “Align Webs” tool to save time and to create the same web pattern for a bunch of trusses. Is as easy as selecting the “main truss” and making the following having the same webs. Sometimes a final work will be required with our old friend VersaTruss.
Maybe your company or customers are in a region where they don´t care much about bracing (Let’s hope the Inspector does!), and you can send your designs to shop without checking for that. You are doing your job properly anyway. But this attitude can be a link in a chain of events that end in a truss falling in the job site and causing injury or a visible fail on the property time later. In fact, most injuries related to trusses on a jobsite are CAUSED by improper bracing.
Would you like it if your home shows a crack in the wall? Or the sheathing starts falling down? It happened to me recently (in a brand new building!) with a leak in the bathroom because someone didn´t take care in properly covering the space between tiles. Nobody was in danger, but the uncomforted situation to me and my neighbor resulted in:
- Going to the builder´s office
- Setting a date for the repairs
- Being there when the workers came
- Not using the bathroom for 3 days, etc., etc.
It was a huge waste of time for everybody involved.
When designing trusses, we must be empathic and try to wear the shoes of the builder and the final customer for a moment and do our best to provide a quality product.
What´s the bracing criterion in your region? Do you take care of that or leave all to the builder? Do you know better tools to work bracing on MiTek´s Software? Please share your thoughts.
You can read Part 1 of this series here.
You can read Part 2 of this series here.
You can read Part 3 of this series here.
Stay tuned for Part 5 in this series.
Javier Dominguez – Design Professional
Gould Design, Inc.