Plumber wants to bore a 3-inch hole through the 2x6 studs of an exterior bearing wall for a shower drain.

IRC Section R502.8 governs boring holes in load-bearing walls.

Key restrictions for 2x6 exterior bearing wall:

• Maximum hole size: 3 inches is allowed (IRC R502.8.1 permits up to 4 inches in studs 6+ inches deep).
• Location: Must be at least 5/8 inch from the stud edge (IRC R502.8.1).
• Spacing: Holes in adjacent studs must be staggered (not aligned vertically) if within 10 inches of each other (IRC R502.8.2).
• Staggering: If boring through multiple studs, offset holes by at least 10 inches vertically.

Critical note: Since this is a bearing wall, you cannot bore through the sole plate or top plate without additional reinforcement (IRC R502.8.3). The 3-inch hole through the studs only is compliant.

Bottom line: Boring a 3-inch hole through 2x6 studs in an exterior bearing wall is permitted per IRC R502.8, provided you maintain 5/8-inch edge distance and stagger holes between adjacent studs. No structural engineer required for this specific scenario.

IRC R602.6 (2021/2024) governs this.

The Limit: In exterior walls and bearing partitions, a hole in a 2×6 stud cannot exceed 40% of the stud depth.

• 2×6 actual depth = 5.5 in.
• Max hole diameter = 2.2 in. (5.5 × 0.40).

The Answer: A 3-inch hole is prohibited. It removes ~55% of the cross-section, compromising the bearing capacity.

Your Legal Options:

1. Header Off: Frame a header (double 2×6 min.) to transfer the load around the penetration. Requires king/jack studs.
2. Go Through the Plate: Bore up through the top plate (R602.6.1 allows up to 50% plate width—~2.75" for 2×6—so 3" is still tight; usually requires a steel tie strap per R602.6.1). Better: run drain between studs and penetrate the bottom plate (non-bearing partition rules often apply, but check local amendment).
3. Move the Wall: Shift the shower layout to align with a stud bay.
4. Engineered Fix: Get a structural engineer’s stamp for a reinforced stud (steel flitch plate, sistered studs with specific nailing schedule).

Notching? R602.6 allows notches ≤ 25% depth (1.375") on the tension side only. Useless for 3" pipe.

Bottom line: Tell the plumber "No" on the 3" bore. Show him R602.6. If he insists, demand the engineer’s letter before you cut.