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I-Joists or Floor Trusses? Ask a Framer

Published March 06, 2024 by
Joe Kannapell
Joe Kannapell

Have you asked a framer lately what floor system they prefer? I did, after seeing a crew I’ve watched use I-joists for the last couple of years now switch to floor trusses. But I wondered why they did so only on town houses. Here’s what I observed:

December 12, 2023 – Clearly, the framers in the first photo had an easier time with trusses this winter, because they didn’t have to cut them to length, or make intricate connections, such as around stairwell openings.

January 21, 2024 – The detached home shown in the second photo is on the other side of the same development, but it has been framed with I-joists. I asked Joe Ford, the Builders FirstSource sales manager, the reason for the difference. His answer was that the home foundations weren’t accurate enough for trusses instead of I-joists. I then tried to ask the framing crew how they like using I-joists, but none on the six-man crew could understand me. However, given the way the joists were lapped, trusses could be installed similarly, minimizing the risk of an inaccurate foundation.

February 2, 2024 – I finally found an English speaker on the framing crew down the road, and when I asked him what he thought, he said

  • while picking up a cut-off piece with his thumb and forefinger: “3½ inches is better”
  • and twisting the cut-off I-joist piece in the next photo: “These are too shaky, unstable” or words to that effect!

And so, the framer joins the plumber, electrician, and HVAC contractor in recognizing that Floor Trusses are better!

Finally, I may have figured out why most town houses have trusses and not I-joists: their foundations have the necessary accuracy, because their slabs are poured monolithically across multiple side-to-side units and tolerances are naturally tighter.

Changing detached homes away from I-joists is difficult in this case because BFS sells both systems and may appear indifferent. However, constantly providing “eye witness” evidence of floor truss advantages, and better price stability, will go a long way. And, it would help to ask the framer and ask for the order!

For more on floor trusses, see my article series on Floor Truss Technology.