Basement bearing wall top plates
What's wrong here?
- The butt joints in the two top plates are offset less than 24 in.
- The joint in the upper top plate does not land over a stud
- A wall carrying floor joists has to be framed with 2x6 studs
- Nothing. This installation is compliant
Show the answer and the code reference
The answer
The end joints in the lower and upper top plates are only about 10 in. apart; the Code requires them to be offset at least 24 in.
Correct choice: 1. The butt joints in the two top plates are offset less than 24 in.
The double top plate acts as a continuous tie and a small beam that spreads joist loads between studs, and it only works as one member if the two layers lap past each other's joints. R602.3.2 (which R602.4 applies to interior bearing walls) requires the double top plate to overlap at corners and bearing-wall intersections and requires end joints in the top plates to be offset not less than 24 in. Here both joints fall within a single 16 in. stud bay, so the plate has a weak hinge point where the lapped floor joists land, and the splice nailing has almost nothing to grab.
How to fix it
Pull the upper top plate back and replace it with a piece that runs at least 24 in. past the joint in the lower plate (a longer board is easiest), then face-nail the lap per Table R602.3(1). Where the plate cannot be replaced, an engineered splice or a steel strap designed for the load is a question for the building official.
Code references
IRC 2018 R602.3.2 — Top plate
Wood stud walls must be capped with a double top plate that overlaps at corners and intersections with bearing partitions. End joints in top plates must be offset at least 24 in.; joints need not occur over studs. Plates must be at least 2 in. nominal thickness and as wide as the studs.
Drills citing R602.3.2IRC 2018 Table R602.3(1) — Fastening schedule
Gives the required face nailing for double top plates and for the lap splice between the upper and lower plates.
Drills citing Table R602.3(1)
2024 IRC:same rule and number. The 24 in. minimum offset of top-plate end joints appears in the 2015, 2018 and 2021 IRC and search results show it carried into the 2024 IRC under R602.3.2. The full 2024 text was not reviewed. Confidence: medium
Minnesota
Minnesota adopts the 2018 IRC with Minnesota amendments as the Minnesota Residential Code (Minn. Rules ch. 1309). No Minnesota amendment to R602.3.2 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 joint in the upper top plate does not land over a stud. R602.3.2 says joints in plates need not occur over studs; the problem is how close the two joints are, not where the upper one lands.
- A wall carrying floor joists has to be framed with 2x6 studs. Table R602.3(5) allows 2x4 bearing studs at 16 in. on center under one floor plus a roof and ceiling (24 in. under one floor only). 2x6 studs come in when a wall carries two floors, which the basement wall of a one-story house does not.
- Nothing. This installation is compliant. R602.3.2 requires end joints in the double top plate to be offset at least 24 in.; these are less than one stud bay apart.