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Forum / Residential Code Discussions /Vaulted gable end walls (Also see code change R602.3)
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Robert Rice
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(3/1/2007 11:52:08 AM)
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Vaulted gable end walls (Also see code change R602.3)

The following is a draft copy of a handout regarding wall support at top and bottom for "out-of-plane" loads. This typically occurs when a flat bottom chord gable-end truss is supplied while the rest of the trusses are vaulted.

The Word doc contains a pic taken from the BCSI-03 truss manual published by Wood Truss Council of America & Truss Plate Institute.
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VAULTED, GABLE END WALLS

The prescriptive provisions of the Oregon Residential Specialty Code are based on platform or balloon framing as stated in the following code section, “R301.1.2 Construction Systems. The requirements of this code are based on platform and balloon-frame construction……”

With platform or balloon framing, the walls are supported at top and bottom to resist wind or seismic loads that are applied to the face of the wall (“out of plane loads”). The bottom is fastened to the floor system (diaphragm) or directly to the foundation. The top of the wall is supported by ceiling or roof diaphragms. The diaphragm is the ceiling or roof sheathing.

In order to support the top of the wall when vaulted trusses are used the gable end truss should be vaulted as well and the wall should be framed up to the bottom of the vaulted truss. Another option would be to not install a truss at the endwall and frame the wall up to the roof sheathing (i.e. “Balloon Framed”). Coordinate these options with the truss manufacturer.

This is consistent with BCSI 1-03, ”Guide to good practice for handling, installing & bracing of metal plate connected wood trusses”, by the Wood Truss Council of America and the Truss Plate Institute, October 1, 2003 as shown below.

(Pic not shown here)

If the wall is not supported at the top by a ceiling or roof diaphragm it is not prescriptive and an engineered design should be provided describing adequate support through multiple top plates, horizontal beam at top of wall, perpendicular interior walls, or other approved methods. Check with you local building department for further information.
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Also, see "2008 ORSC 602.3" in the code change forum.

If you want a copy of the Word doc let me know and I'll send it you you.

Robert Rice
structdesigner@yahoo.com