Residential Building Inspector B1Floor ConstructionMedium
An inspector is reviewing the framing for a floor that includes a large opening (e.g., for a stairway). The opening requires a header joist and trimmer joists. What is the primary function of the header joist in this scenario?
- ATo prevent the floor joists from twisting or rotating at the opening.
- BTo increase the overall rigidity of the floor assembly.
- CTo provide a nailing surface for the subfloor around the opening.
- DTo transfer the load from cut floor joists to the trimmer joists.
Show answer & explanationAnswer & explanation
Correct answer: D. To transfer the load from cut floor joists to the trimmer joists.
In floor framing for openings, the header joist (or header beam) runs perpendicular to the main floor joists and is supported by the trimmer joists. Its primary function is to collect the loads from the cut common joists that terminate at the opening and transfer those loads to the stronger trimmer joists.
Why the other options are wrong
- A. This is more a function of blocking or bridging, not the primary role of a header.
- B. While it contributes to rigidity, its specific role is load transfer from cut joists.
- C. While it does provide some nailing surface, its main role is structural load transfer.
Floor Framing Header Joist
A structural member spanning across an opening in a floor system, supporting the ends of cut common joists and transferring their loads to adjacent trimmer joists.
- Used for stairways, chimneys, and other large openings.
- Orientation is perpendicular to common joists.
- Must be adequately sized and connected to trimmer joists.
Memory trick: Headers Hold, Trimmers Take, Common Cuts.