At that opening you find the header built up in two plies with a splice over the middle of the opening, the wall sheathing cut along the header line so that separate sheets cover the header and the narrow piers below it, and the strap called for over the header not installed. The piers themselves are the correct width and are anchored. How should the inspector judge the portal frame?
- Reject it; a portal frame depends on a continuous header across the opening and on sheathing that runs unbroken over the header into the piers with the specified fastening and strapping
- BAccept it; the piers are the braced elements at this opening and the header above them is only a gravity member carrying the wall above it, so a splice in it does not affect the bracing at that opening
If the piers alone were the braced elements they would be far too narrow to qualify. The whole reason the method permits piers this narrow is the frame action the continuous header provides.
- CAccept it; the joint in the sheathing is acceptable because it lands on framing, which is all that the sheathing provisions ask of a panel edge anywhere in a braced exterior wall
Landing a joint on framing satisfies an ordinary sheathing requirement. In a portal frame the sheathing has to run unbroken across the header-to-pier junction, which is precisely where this joint was cut.
- DReject it, and require the opening to be narrowed until an ordinary braced wall panel of the required length will fit on each side of the garage door opening in that wall
Narrowing a garage door opening is an enormous change to correct a detailing failure. The portal frame can be rebuilt in place, and inspectors do not impose design changes to fix workmanship.
Why A is correct
The method works as a frame. Continuity of the header, sheathing lapped over the header into the piers with the specified nailing, and the strap tying them together are what create the frame action, and each of those three is missing or broken here.
What this question is testing
Whether the candidate understands that a portal frame is an assembly whose parts must be continuous and connected, and can identify which specific departures destroy the method rather than merely weakening it.
On the job
Portal frames at garage fronts are the highest-consequence bracing detail in a typical house, and they are also the least understood on site. Framers treat the header as a header and sheathe the wall in the usual sheets. Inspectors go to the garage opening first on a bracing inspection, look for a single unbroken sheet wrapping the header, count the nails in the prescribed pattern, and confirm the straps and anchors before anything is covered.
Memory technique
A portal frame is one piece or it is nothing.
Exam tip
In a portal frame, continuity is everything: continuous header, continuous sheathing, connected together.
Where to look it up
IRC Chapter 6 wall bracing, the portal frame methods and their figures showing header continuity, sheathing lap and strapping.