I-Joists and Deflection To the Editor: I read with interest John Siegenthaler's article "Wood I-Joist Fundamentals" (Practical Engineering, 10/95). I am curious why the author did not mention deflection in this article, as this often controls in bending member design. John "Buddy" Showalter, P.E. American Wood Council Washington, D.C. John Siegenthaler responds: The purpose of the article was to illustrate to builders (who are often more familiar with hefty solid-sawn lumber) how an I-joist, with its thin profile and light weight, can handle the bending forces present in a floor joist. Nevertheless, your point is a good one; namely, that deflection — of either a solid-sawn joist or an I-joist — is usually the limiting factor in joist selection. Most building codes allow
