Which Product Is Better… I-Joists or Floor Trusses? Part 2

Which Product Is Better… I-Joists or Floor Trusses? Part 2

This topic has received so much attention on our blog that we thought we would write another article about it. To see part 1 of this series, click here.

This debate, I don’t feel is as hot of a topic as “Rafters vs. Trusses”, at least not in the area that I live. However, it is still one that is worthy of discussion never-the-less. I have designed I-Joist for many years using software called Javelin, produced by Weyerhaeuser. While there are many others out there such as Boise Cascade (BC Framer), Georgia-Pacific (FASTBeam) and Louisiana-Pacific (LP Solutions) just to name a few, I feel that Javelin is superior.

My previous employer has what’s called Next-Phase or as we call it, “Fast Frame.” With “Fast Frame” it is just like a jig saw puzzle. The shop has the ability with a computer controlled saw, not much unlike a truss saw, to cut every piece of a floor whether its “I’s” or EWP to the exact length that is needed for the job site. This leaves absolutely no waste and reduces labor on the job site. I would call this a very big bonus for any builder. With floor trusses being built this way to begin with, it was a huge step for the world of I-Joists.

The biggest advantage in my opinion in using I-Joists is simple: Efficiency. EWP is resourceful for many reasons, some of which you may already be aware of, some of which you may not be. In the following I will list pros and cons to both and the advantage.

Mechanical equipment – Pros & Cons


ADVANTAGE: Floor Trusses

  • Floor trusses have a distinct advantage for being mechanical equipment friendly. With the ability to design chase openings for ductwork through them, this is a big advantage. But let’s say there is a change on the job site and the truss company was not informed (Which never happens right?) and the ductwork must be shifted. The openings in the webbing will allow for this adjustment to happen seamlessly. With this type of flexibility, who wouldn’t want floor trusses?
  • With I –Joists, the holes that you can actually cut into each joist can be pretty small. The holes also must follow certain parameters. Sometimes this is very limiting and you must stay within certain locations of the joists to use the holes. Let’s not forget if you cut into a flange, big no-no, you’re going to need a new joist.

Spanning the distance – Pros & Cons


ADVANTAGE: Floor Trusses

  • Floor trusses can clear-span with the same floor ratings much further than any I-Joist product. This is very beneficial to the frugal home builders and home owners out there. Let’s face it though; aren’t we all trying to be more frugal with everything we do? Who wants to put in that extra steel beam and posts or 3-4ply LVL to carry some “I’s” those extra 3’ or 4’ because their span rating its good for that distance? Those beams could add up to several hundred (even thousands) of dollars.
  • I-Joists on the other hand may need an increased depth or decreased spacing to span the very same distance, using the very same design criteria. The bridging and blocking can be increased to “shore” up the floor, but the risk is run that it will not be input

Unique conditions: Step-Down Balcony – Pros & Cons


ADVANTAGE: Floor Trusses

  • What happens where there is a cantilevered balcony condition? This all but eliminates I-Joists.
  • With floor trusses, the step-down can be built right in to the design, for minimal additional cost. This creative design is a very nice alternative and is very fun to design!

Unique conditions: Keyed Connection – Pros & Cons


ADVANTAGE: Floor Trusses

  • What happens where there is an interior bearing wall? Or the floor truss needs to be longer than 40’? Most floor truss tables only allow a 40’ span to be built. Floor trusses can be “keyed” and this will allow a longer overall span. On shorter spans, this will all but eliminate the splices needed and keep the truss at or below standard board lengths.
  • With I-Joists, this design is not possible.

Site modifications – Pros & Cons



  • Floor trusses cannot be modified on site, due to a field discrepancy, without an engineer’s seal. This limits any modifications that may need to be done on the job site, for a variety of reasons.
  • I-Joists have what is called “span charts” that can be utilized by the carpenters to allow for a variety of job site modifications. No more paying for extra sealed engineering to modify the product when the building is out of square, or not per plan dimensions.

Cost-effectiveness – Pros & Cons



  • I think is a big one. “I’s” are significantly cheaper than Floor trusses. Money that can be used on other things throughout the house building process. On top of that, “I’s” are also easy to replace or cut up if a break happens, a repair is needed, mistake is either the design or by the guy who poured your foundation out of square.
  • With floor trusses, if any of these things happen, it can be a nightmare to take care of. Engineering repair letters will be needed along with lengthy fixes. The costs mount up fast. Delays are certain. Which leads me to my next subject…

Jobsite delays – Pros & Cons



  • Since you can cut every single joist you need to make fit, delays are minimized. A framing crew member can get a new one sent out from the yard the same day, or even pick one up them self. I-Joists can be purchased from most any lumberyard and the product equivalency from one manufacturer to another is extremely compatible.
  • That is not happening from a truss company (Getting a new floor truss sent out the same day should you need it). The truss has to be designed, sealed, built and then delivered from the same truss manufacturer. When there is an issue with the floor truss, expect some type of delay.

Hopefully with these few detailed examples of both; Floor Trusses and I-Joists, you can understand why I think “I’s” are the better product. The cost-effectiveness alone is worth its weight in gold. Add onto the fact that “I’s” are now being cut to fit, and you have a revolution in the framing industry. Now if were to combine them…

We would have the magic product which is the best of both worlds. What if the I-Joist and the floor truss could be combined? Well it can. All the flexibility of joists and the sturdiness of trusses combined into one product. The question in my mind is: Why isn’t this product in more demand?


These are just a few of the pros and cons. Perhaps I will think of more and write another article on them. That all depends on your response! How are you seeing the pros vs. the cons of these two products?

Zach Failing – Design Professional

Gould Design, Inc.

6 thoughts on “Which Product Is Better… I-Joists or Floor Trusses? Part 2

  1. We are planning to renovate our home, last year this would have not been a problem.
    Now they have change the municipal bylaws for our zoning. Our current home was modular constructed home. Since we had invested a lot of money into upgrades we thought we could raise it and build underneath and match up the bearing walls. Now the new bylaw require the second story to be set back from the side property lines 1 meter further away than the main floor on both sides. Doing this we have to now come up with a new support structure (that does not interfere with the main floor plan). Could we lower the second story on top of an engineered trussed floor/ceiling of the new ground floor? Center-line support would be there in any case. Any ideas?

    Please reply,
    Thank you!

    Tony Frei

    1. Tony,

      Thanks for the note. Unfortunately, your question falls outside of the scope of this BLOG. I would suggest that you consult with an engineer who is familiar with the region in which this project would be undertaken.

      We hope your project goes well!

  2. The other thing he didn’t mention was the I-joist run 16″ OC where a truss will run 24″ OC therefore the cost for trusses will only be a couple hundred dollars more than I joists. You save that money in your mechanical install times easily.

  3. There are many companies that offer floor trusses that are trimmable on each end. Why does the author of this article make it sound like they do not yet exist? I wish that option was discussed here.

  4. Open joist TRIFORCE!!!! The best of both worlds!!!

    I really enjoyed both parts of this article. There is no reason you have to choose one product over the other. You can have the best of both worlds by using the Open-joist TRIFORCE. The TRIFORCE is an open-joist that is trimmable up to 2ft in the field.

    The TRIFORCE offers the load capacity, open web (for running mechanicals), and design flexibility of a custom floor truss without the manufacturing lead-time or long job-site delays.

    The TRIFORCE also offers the field flexibility (trimmable up to 2ft), short lead times and cost effectiveness of the I-joist.

    Our designers can provide you with placement plans, joist sizings or joist calcs if needed.

    As you can see the Open-Joist TRIFORCE is the way to go.

    For more information please visit our website at http://www.ojtriforce.com or call me @ 203-917-1371.

    Matt Loiselle