Laundry vent through the top plate

The answer

Both top plates of this bearing wall are notched about three-quarters of their 3-1/2 in. width for the vent, and there is no 16-gauge galvanized tie fastened across the cut, which R602.6.1 requires when more than 50 percent of the plate is removed.

Correct choice: 1. The double top plate of this bearing wall is notched more than half its width, and no galvanized steel tie spans the cut

The joists landing and lapping on the plate make this an interior bearing wall. The double top plate ties the wall together and spreads joist loads to the studs; cutting both plates nearly through at one point breaks that continuity. R602.6.1 says that when piping or ductwork in an exterior wall or interior bearing wall requires cutting, drilling or notching the top plate by more than 50 percent of its width, a galvanized metal tie at least 0.054 in. thick (16 ga) and 1-1/2 in. wide must be fastened across the opening with eight 10d nails on each side, extending at least 6 in. past the opening. Here only about 3/4 in. of wood is left at the back of the notch and the face of the plate is bare. Drywall on the far side does not trigger the exception; it applies only where wood structural panel sheathing covers the entire notched side of the wall.

How to fix it

Code reference

• IRC 2018 R602.6.1 — Drilling and notching of top plate

  Where piping or ductwork in an exterior wall or interior load-bearing wall requires cutting, drilling or notching the top plate by more than 50 percent of its width, a galvanized metal tie not less than 0.054 in. thick (16 ga) and 1-1/2 in. wide must be fastened across and to the plate at each side of the opening with not less than eight 10d (0.148 in.) nails each side, extending at least 6 in. past the opening. Exception: where the entire side of the wall with the notch or cut is covered by wood structural panel sheathing.

  Drills citing R602.6.1

2024 IRC:same rule and number. Search-result excerpts of the current IRC text show the same 50 percent trigger, 16 ga by 1-1/2 in. galvanized tie, eight 10d nails each side, 6 in. extension past the opening, and the wood structural panel exception. Not checked line by line against the printed 2024 IRC. Confidence: medium

Minnesota

Why the other choices are wrong

• A plumbing vent may not pass through a top plate; it must be offset into the joist bay below the plate. Vents and drains routinely pass through top plates. R602.6.1 allows it and only asks for a steel tie when more than 50 percent of the plate width is removed.
• Top plates may never be notched; only bored holes are allowed. The IRC does not distinguish notches from bored holes in top plates. Any cut, bore or notch over 50 percent of the plate width in an exterior or bearing wall needs the tie described in R602.6.1.
• Nothing. The drywall on the other side of the wall makes up for the notch. The R602.6.1 exception applies only when wood structural panel sheathing (plywood or OSB) covers the entire side of the wall that is notched. Gypsum board on the opposite side does not qualify.