Do You Know Your ANSI/TPI 1 Chapter 3 Numbers?

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Issue #17315 - October 2025 | Page #33
By Glenn Traylor

Inspired by frequent requests for a quick reference, I’ve created a single-sheet ANSI/TPI 1 Chapter 3 guide—similar to a CliffsNotes version of the standard. Please note that important details are omitted; for a complete understanding, consult the full standard, National Design Standard for Metal Plate Connected Wood Truss Construction, available from the Truss Plate Institute website: https://www.tpinst.org/documents.

3 inspections per week per shift per station are required (Section 3.3.2)

3/4” variation from design length (Section 3.5.1)

1/2” variation from design height (Section 3.5.1)

1/2” variation truss to truss length (Section 3.5.1)

1/4” variation truss to truss height (Section 3.5.1)

No less than 1 critical joint per truss selected for inspection each week (Section 3.7.1)

1/8” midpoint variation of critical plate if no polygon is present on critical joint (Section 3.7.2.1d)

10% plus or minus is the allowable plate rotation variation unless otherwise noted (Section 3.7.3)

1/32” is the maximum allowable embedment gap of an installed connector (Section 3.7.5.1)

1/8” is the maximum member to member gap except for floor chords (Section 3.7.6.1)

1/16” is the maximum member to member gap for floor chords (Section 3.7.6.1)

3/4” is the minimum width of a shimming metal to correct member to member gap (Section 3.7.6.3)

1/4 of tooth length is the maximum tooth length visible for flattened teeth (Section 3.7.7.1)

0% is the value of the area where wood was removed while removing a connector (Section 3.9.2)

50% is the value of the area where teeth were removed but no wood was removed (Section 3.9.3)

Although a summary sheet may assist in recalling important figures, it should not substitute for a thorough understanding of the standard. I encourage dedicating a few minutes to reading the standard to ensure complete comprehension.

Glenn Traylor

Author: Glenn Traylor

Structural Building Components Industry Consultant

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