Can a gable end stud wall be supported by an open span rim joist?
wolfe8105
| Posted in Building Code Questions on
I want to build a house that is 40 ft wide. i want a vented crawlspace. there will be 3 stem wall foundations running the 80 length of the house. splitting the floor span to two 20 ft spans. i will use common trusses. the issue is the gable ends. if i am required to use balloon framing as in 602.3 suggests. then table 602.3.1 for 12 ft stud walls plus the height of the roof states that it is only good for the condition on 12 ft floor span. since this is the gable end does this still apply?
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Wolfe, I assume you're referring to the International Residential Code (IRC)? Which year? In the 2009-2015 IRC, table 602.3.1 lists fastener requirements--nothing about stud length or joist/beam span.
I assume your house will be a single story with a flat ceiling? "Common truss" is not really a truss type, and I just want to be sure we're talking about a roof truss and not a floor truss of some sort.
The normal way to build with a truss roof is to frame the walls all at the same height, and use a gable end truss at the gable end, above the top plate. Depending on the design of your wall and your floor system, you may or may not need additional shear bracing at the ceiling plane. This can be accomplished with diagonal braces or a diaphragm of plywood or OSB, but it's not usually necessary. You do need something to keep the walls tied into the trusses, but that is usually done with a strongback above the bottom chord of the truss.
Your floor span is very large, so in order to create shear bracing, you should probably have an engineer look at your design to make sure it is adequately braced.
Yes irc 2013. 602.3(1) is the fastener. 602.3.1 is the max allowable stud wall height. It's foot note b that concerns me. Correct just flat ceiling. 16" I joist for the floor. I thought the flat truss on top of top plate created a hinge. That's why they want continuous from the sole plate to the roof. The code doesn't mention strongback but the truss manufacturer does.
Thanks for the heads up regarding shear bracing.
You must mean IRC 2012. Interesting; I have spent very little time with that edition, as the places I work use either the 2009 or 2015 code. The table you reference is not in either of the other editions. In any case, gable end walls are not supporting a roof so I think you're ok, but you should check with your code enforcement officer to make sure that he/she interprets it the same way.
There are various ways to brace the hinge at the wall/gable truss joint. IRC 2012 R602.3 reads, 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." You are choosing the read "support at the roof" as your best option, which is fine, but the usual approach is to brace the hinge point another way. If your truss supplier did not provide a diagram, I would check with a licensed engineer. Your house is large and the loads on the wall could be significant.
Farther down in Chapter 6 are the wall bracing requirements, which may be affected by your floor situation. An engineer could also help you with that part of your design.