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Don’t Forget! You Saw it in the
January 2017 #10210 Page #34
Question of the Day... Stan Sias
Why do some still insist on placing flat bottom chord gable end frames adjacent to vaulted or scissor trusses when the codes clearly do not allow such framing without special engineering requirements? Can you point me to the code sections that say “No, thank you!”?
This is a great question and clearly a bad practice, yet we see these scenarios continue to play out regularly on both professionally and DIY framed projects across most, if not all, of the country. Perhaps the best way to start this discussion is with the appropriate ICC code provisions. What do the Codes say and what are our industry best practices? IRC 2009 & 2012 Chapter 6 (Wall Framing), Section R602.3 states in part: Studs shall be continuous from support at the sole plate to a support at the top plate to resist loads perpendicular to the wall. The support shall be a foundation or floor, ceiling or roof diaphragm or shall be designed in accordance with accepted engineering practice.
IBC 2009 & 2012 Chapter 23, Section 2308.9.1 states in part: Size, height and spacing. The size, height and spacing of studs shall be in accordance with Table 2308.9.1 except that utility-grade studs shall not be spaced more than 16 inches (406 mm) o.c., or support more than a roof and ceiling, or exceed 8 feet (2438 mm) in height for exterior walls and load-bearing walls or 10 feet (3048 mm) for interior nonload-bearing walls. Studs shall be continuous from a support at the sole plate to a support at the top plate to resist loads perpendicular to the wall. The support shall be a foundation or floor, ceiling or roof diaphragm or shall be designed in accordance with accepted engineering practice.
What does BCSI say about this scenario from a best practices perspective? In service, Gable End Frames also experience lateral Loads parallel and perpendicular to their plane. The Gable End Frame shall be incorporated into the wall design by the Building Designer. Gable End Frames rely on properly designed and installed Structural Sheathing, Bracing and Connections to the bearing wall, and roof and Ceiling Diaphragms to be able to adequately transfer lateral Loads acting parallel and perpendicular to its plane. If the lateral Load is large enough, and the vertical studs are long enough, the Gable End Frame may require Bracing to prevent it from rotating at the Gable End Frame/end wall interface, along with Diagonal Bracing and/or Web Reinforcement to prevent vertical Webs from bending excessively. Serviceability failures often occur if the Gable End Frame is not properly braced. Gable End Frame Bracing/reinforcement helps prevent these types of serviceability failures and safely transfers forces from the Gable End Frame into the associated Diaphragms.
Let’s look at some real life examples of what happens when we don’t follow the codes and industry best practices.
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