How to Take a Proactive Approach to the Truss Design Layout Process
There are many things to take under consideration when developing a layout for truss design. A blueprint is provided with instructions and details to aid in the creation of an accurate layout. It is of extreme importance to be fluent in the language of architecture. The key to ensuring layout competency is to generate and follow a process that, when applied to a plan yields a complete and correct layout.
First things first, read the plan carefully. Make sure to note any significant details. Generally, the blueprints are referred to numerous times throughout the process of creating a layout.
To get started, ask yourself a few questions and search for relevant information:
- Is this the most recent blueprint?
- Do I have loading information for roof application, wind, snow, drift, mechanical units, etc.?
- Which building code is to be used? Are the elevations all present in the plans?
- Do I have a wall section?
- Verify all dimensions are present.
- Decipher the wall heights and widths.
- Determine need for cladding (brick/stucco, etc.) and decide whether the plan is dimensioned to the stud or the cladding.
- Locate the roof/ceiling pitch and overhang length(s). Note if the overhang is plumb or square-cut. Also, determine if the overhang length includes fascia.
- Figure out the heel height, if necessary, based on the pitch, overhang length, and fascia.
Using your company’s Quality Assurance sheet can be a huge preventer of wasted time during this process.
Once this information has been ascertained, putting the layout together can begin. It is critical to know if you have all of the relevant information before proceeding any further.
Input the walls first. How the walls are “set” depends entirely on preference. The settings concerning height, width, cladding, and etc. may be changed while the walls are input, but it is best to set all this up proactively. Another option would be to completely input the walls and then make alterations. Either way, the plans must be referenced while the walls are being drawn.
This is a good time to create any interior walls and or any beams that will be needed for bearing as well. After all the walls and beams are where they need to be, check the 3D view and make sure that everything is at the proper elevation and looks right.
Once all aspects of the walls are verified to be correct, the next step is to assign planes. Both roof and ceiling changes are constructed at this time. The order of input concerning the ceiling or roof planes is based on preference. I like to input the roof planes first, going clockwise. Going back and forth between the elevations section of the blueprint and the layout software is important. Making sure that the planes match the blueprint is necessary. Input roof planes one by one and then cut the planes accordingly.
Any ceiling changes noted at the beginning are now important. Highlighting or noting the ceiling changes makes them easy to find. Look through the plan and find any ceiling changes. Next, determine where the ceiling planes need to go using the dimensions from the layout, then cut the planes. I like to cut the vaulted ceiling plane to the outside of the gable wall to make sure the gable truss will match the next truss in the run. This will save you from having to “re-calc” it later.
This is a good point to check the 3D view again and make sure there aren’t any issues with what has been input thus far.
Once I have verified all of the above, I now refer back to section 2 of my checklist and determine what else I may need to consider for this project. Things such as:
- HVAC/FAU locations.
- Attic access.
- Rake/balloon walls.
- Upturned beams.
- Chase locations.
- Etc., etc.
After a thorough, proactive review, I can select the items on my checklist I need to refer back to later on or that I have questions on.
At last, we get to put trusses on the layout! When applying the trusses, think about the most cost-effective and construction friendly manner to arrange them. Basically, trusses should be laid out so there are as many like trusses as possible. The layout needs to look clean and well-organized. Different methods of laying out the trusses appear below. Neither approach is necessarily wrong; however; the method on the right will provide smaller, more manageable, cost-effective trusses than those on the left.
Figuring out the best way to set the trusses takes a bit of trial and error at first, but with experience, it becomes a natural process. Now, we want to refer to the 3D view again. Verify that there aren’t any rogue chords; things “sticking through the roof”, to make sure that all the trusses are adhering to the planes that were cut.
These chord errors resulted from adjusting the span of the truss on the left end and not re-assigning the top chord planes. This mistake is both easily made and fixed, but may have been missed if not for the 3D viewer.
The final step in creating a layout is to note anything of importance. When looking through the blueprints, the architect provided detail notes and direction for how the building would be put together. Do the same favor for the person looking at the truss layout and actually “setting” the trusses on the jobsite. Make a note of all the pertinent information regarding how to put the structure together and what is going on within the created truss layout. For example, a “BALLOON FRAME” detail note along wall 2 would be very helpful.
What tools do you use in the layout process? What methodologies? Please leave your comments below.
Ashley Casey – Design Professional
Gould Design, Inc.