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Component Manufacturing dverti$ dverti $ er
Don’t Forget! You Saw it in the
Adverti$$er
May 2022 #14274 Page #43
Is Perfect Lumber Required to Make Great Trusses? ue to the nature of wood, lumber characteristics can vary in every piece. Even “in grade” lumber can have drastic variations in performance. How can we deal with and adjust for natural defects and variability? We have discussed roof trusses in previous articles, including “Does Your Truss Plant Understand the Importance of Tooth Count?” and “Who is Responsible for Lumber Quality in Your Trusses?” Now, let’s take a closer look at floors.
By Glenn Traylor
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Floor Trusses Here’s an example. Traditional 4 x 2 floor trusses are somewhat unique in that they depend on narrow faces, normally 1 ½”, to transfer loads to chords then ultimately bearings. This can present a slightly different challenge compared to 2 x 4 roof trusses, where we have wider surfaces. The photos illustrate Plate Placement drawings for a typical floor truss. The circles numbered 1,2,3 represent the allowable defect each connection can have while still providing adequate tooth holding to complete the mission. The smaller the circle, the less the allowable defect. Circles 1 and 2 allow very little defect while 3 is a little more generous. Due to the narrow face, we cannot neglect identifying defects under the plated area given its impact on joint performance.
In the next photo of an end condition (Bearing), notice points 4 and 5. A very small amount of defect is allowed. More defect is allowed on the bottom chord. This sort of condition does not allow for much defect including wane situations.
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