Stair opening in the second floor
What's wrong here?
- The header and trimmers are single 2x10s across an opening wider than 4 ft; both must be doubled
- The header must hang from the trimmers in joist hangers once the opening is wider than 4 ft
- Tail joists may not hang from a header; they must bear on a wall
- Nothing. This installation is compliant
Show the answer and the code reference
The answer
The stair-opening header spans about 62 in. (5 ft 2 in.), but the header and both trimmer joists are single 2x10s. R502.10 requires both to be doubled when the header span exceeds 4 ft.
Correct choice: 1. The header and trimmers are single 2x10s across an opening wider than 4 ft; both must be doubled
At a floor opening the header picks up every tail joist and delivers that load to the trimmers at its ends, so each trimmer carries its own share of floor plus half the header. R502.10 allows a single header the same size as the joists only up to a 4 ft span, and a single trimmer only when that single header sits within 3 ft of the trimmer's bearing. Over 4 ft, the header and the trimmers must be doubled and big enough for the tail joists they carry. Here the tape reads about 62 in. between trimmers and the header carries three tail joists, but every member around the opening is a single 2x10. That gives you a bouncy, sagging stair edge and end nails carrying more than they should.
How to fix it
Add a second full-length trimmer on each side, bearing at both ends, and a second header ply, nailed together per the fastening schedule. Hangers at the header-to-trimmer connections are good practice at this span and become mandatory once the header span exceeds 6 ft.
Code reference
IRC 2018 R502.10 — Framing of openings
Openings in floor framing must be framed with header and trimmer joists. A header spanning 4 ft or less may be a single member the same size as the joists, carried by a single trimmer if the header is within 3 ft of the trimmer's bearing. Where the header span exceeds 4 ft, the trimmers and header must be doubled and big enough for the tail joists they carry. Approved hangers are required at the header-to-trimmer connections when the header span exceeds 6 ft.
Drills citing R502.10
2024 IRC:same rule and number. Summaries of 2024-based codes show the same R502.10 text: a single header up to 4 ft, doubled header and trimmers over 4 ft, approved hangers over 6 ft, and tail joists over 12 ft on framing anchors or 2x2 ledger strips. Not checked line by line against the printed 2024 IRC. Confidence: medium
Minnesota
Minnesota adopts the 2018 IRC with Minnesota amendments as the Minnesota Residential Code (Minn. Rules ch. 1309). No Minnesota amendment to R502.10 is known. DLI is adopting the 2024 IRC as the next edition; see the 2024 IRC note.
About the Minnesota Residential CodeWhy the other choices are wrong
- The header must hang from the trimmers in joist hangers once the opening is wider than 4 ft. R502.10 makes header-to-trimmer hangers mandatory only when the header spans more than 6 ft; this one spans about 5 ft 2 in. The 4 ft trigger is for doubling.
- Tail joists may not hang from a header; they must bear on a wall. Tail joists normally frame into the header in hangers. R502.10 only adds a specific rule for tail joists over 12 ft long, which need framing anchors or 2x2 ledger strips.
- Nothing. This installation is compliant. A single header and single trimmers are only allowed when the header spans 4 ft or less (R502.10); this header spans about 62 in.