Drilling and Notching Wall Studs — IRC 2018

What IRC 2018 § R602.6 requires

IRC 2018 R602.6 permits notches in bearing wall studs up to 25 percent of the stud width and holes up to 40 percent. For non-bearing studs, notches can be up to 40 percent of the width and holes up to 60 percent. When limits are exceeded, a steel nail plate must protect any notch within 1.5 inches of the face to prevent puncture of pipes or wires by fasteners.

Section R602.6 of the IRC 2018 sets dimensional limits for cuts in wood studs for utilities:

Bearing wall studs: Notches on the edge of a stud may not exceed 25 percent of the stud width. For a 2×4 stud (actual width 3.5 inches), the maximum notch is 0.875 inches (25% × 3.5). Holes drilled through the stud face may not exceed 40 percent of the stud width — a maximum 1.4-inch diameter hole for a 2×4 stud. These limits preserve the stud's axial load capacity, which drops dramatically when cross-sectional area is significantly reduced.

Non-bearing wall studs: The limits are relaxed because non-bearing studs carry no significant axial load. Notches may not exceed 40 percent of the stud width. Holes may not exceed 60 percent. For a 2×4 non-bearing stud, these translate to 1.4-inch maximum notch and 2.1-inch maximum hole diameter. This allows larger utility chases through non-bearing partitions.

Nail plate protection: When a notch or hole in a stud is within 1.5 inches of the face of the stud (the face that will be covered by wall sheathing or drywall), a 1/16-inch-thick steel nail plate must be installed over the notch or hole. This prevents nails or screws from the wall finish from penetrating and damaging the pipe or wire in the notch.

Double-stud assemblies: If a stud is notched beyond the allowable limit and the framing contractor wants to maintain structural performance, an alternative is to sister a full-depth new stud alongside the notched stud. The sister stud must be properly nailed to restore full section area.

Why This Rule Exists

Wall studs are vertical compression members that carry the weight of floors and the roof above. When a notch cuts into the stud cross-section, it reduces the area available to resist axial compression and creates a stress concentration at the notch root. A notch too deep in a bearing stud can cause the stud to buckle laterally or split along the grain at the reduced section. The percentage limits in R602.6 are calibrated to keep the remaining cross-section sufficient for the stud's column capacity. The nail plate requirement prevents the separate but equally dangerous problem of a fastener puncturing a water pipe or wire hidden in a notch.

What the Inspector Checks at Rough and Final

At the rough framing and rough mechanical/electrical inspection, the inspector checks:

• Notch depth in bearing studs — must not exceed 25% of stud width.
• Hole diameter in bearing studs — must not exceed 40% of stud width.
• Notch and hole limits in non-bearing studs — 40% and 60% respectively.
• Steel nail plates installed wherever a notch or hole is within 1.5 inches of the wall face.
• Notch locations — notches should not be at the top or bottom of a stud unless unavoidable, as these are high-shear locations.
• Multiple closely spaced holes — a concentration of holes in the same stud at similar heights is a concern for remaining net section.

What Contractors Need to Know

A 3/4-inch notch for a 3/4-inch PEX pipe in a 2×4 bearing stud exactly hits the 25% limit — marginal. Where possible, route pipes through non-bearing studs instead, where a deeper notch is permitted. Plan mechanical rough-in routes before closing walls to avoid excessive stud modification.

Always install nail plates immediately when notches are cut — do not plan to add them later. Drywall contractors and other trades can inadvertently drive a screw into an unprotected notch location before you return. Make nail plate installation part of the immediate notching workflow.

For 2×6 bearing walls, the limits apply to the 5.5-inch actual width. A 25% notch limit gives 1.375 inches of allowable notch depth, which accommodates most 1-inch nominal pipe runs. A 40% hole limit gives 2.2 inches, which can accommodate a 2-inch drain pipe with margin.

In utility-dense walls containing both plumbing and electrical runs, the cumulative effect of drilling and notching from different trades can exceed the individual limits even when each trade stays within its own allowance. There is no provision that allows the aggregate of one trade notch plus another trade hole to exceed the combined stud section reduction limit. If both a 1.5-inch pipe and a 3/4-inch conduit must pass through the same bearing wall stud, the combined reduction in stud area must be evaluated. This often requires doubling studs at the utility run location or rerouting one utility to an adjacent non-bearing wall where the limits are more generous.

Nail plates are required whenever a notch or hole is within 1.5 inches of the face of the stud, the distance where a drywall nail or screw could otherwise hit the pipe or conduit during finish work. The nail plate must cover the full vertical extent of the utility run close to the stud face. Nail plates are a routine inspection item, and their absence generates an automatic correction notice. Install them as each notch or hole is drilled, not as a batch after rough-in is complete. A single plate that does not cover the full run of a diagonal utility is also considered non-compliant.

In utility-dense walls containing both plumbing and electrical runs, the cumulative effect of drilling and notching from different trades can exceed the individual limits even when each trade stays within its own allowance. There is no provision that allows the aggregate of one trade notch plus another trade hole to exceed the combined stud section reduction limit. If both a 1.5-inch pipe and a 3/4-inch conduit must pass through the same bearing wall stud, the combined reduction in stud area must be evaluated. This often requires doubling studs at the utility run location or rerouting one utility to an adjacent non-bearing wall where the limits are more generous.

Nail plates are required whenever a notch or hole is within 1.5 inches of the face of the stud, the distance where a drywall nail or screw could otherwise hit the pipe or conduit during finish work. The nail plate must cover the full vertical extent of the utility run close to the stud face. Nail plates are a routine inspection item, and their absence generates an automatic correction notice. Install them as each notch or hole is drilled, not as a batch after rough-in is complete. A single plate that does not cover the full run of a diagonal utility is also considered non-compliant.

In utility-dense walls containing both plumbing and electrical runs, the cumulative effect of drilling and notching from different trades can exceed the individual limits even when each trade stays within its own allowance. There is no provision that allows the aggregate of one trade notch plus another trade hole to exceed the combined stud section reduction limit. If both a 1.5-inch pipe and a 3/4-inch conduit must pass through the same bearing wall stud, the combined reduction in stud area must be evaluated. This often requires doubling studs at the utility run location or rerouting one utility to an adjacent non-bearing wall where the limits are more generous.

Nail plates are required whenever a notch or hole is within 1.5 inches of the face of the stud, the distance where a drywall nail or screw could otherwise hit the pipe or conduit during finish work. The nail plate must cover the full vertical extent of the utility run close to the stud face. Nail plates are a routine inspection item, and their absence generates an automatic correction notice. Install them as each notch or hole is drilled, not as a batch after rough-in is complete. A single plate that does not cover the full run of a diagonal utility is also considered non-compliant.

What Homeowners Get Wrong

DIY plumbers often cut deep horizontal channels (notches) across the face of several adjacent studs to run a pipe horizontally in a wall. These horizontal notches across multiple studs simultaneously eliminate the bearing capacity of those studs in that zone, potentially causing a section of the wall to become structurally weak. Horizontal utility runs should use holes drilled through the stud center, not notches cut across the face.

Another common error: homeowners assume that because a plumber or electrician did the notching, it must be code-compliant. Tradespeople sometimes exceed notching limits when it makes their work easier, especially if they do not expect an inspection before walls are closed.

In balloon-framed construction — an older framing method where studs run the full height from sill to rafter — the notching and boring limits still apply, but the stud height is much greater than in platform framing. The 2x4 or 2x6 stud in a balloon-framed wall may be 16 to 20 feet tall, and holes drilled at multiple levels accumulate. Because each individual hole must still comply with the single-floor requirement, the engineer of record should review any balloon-framed wall that has multiple utility penetrations at different heights to confirm that the stud section remains adequate for the cumulative reduction.

State and Local Amendments

The drilling and notching limits in IRC 2018 R602.6 are adopted without modification across TX, GA, VA, NC, SC, TN, AL, MS, KY, and MO. These limits are based on engineering analysis of wood column behavior and are not significantly influenced by local climate conditions. However, in high-wind or seismic areas where the structural sheathing is part of the lateral force-resisting system, notching or drilling into shear wall studs may be further restricted by the structural engineer's requirements.

IRC 2021 did not change the stud drilling and notching percentage limits in R602.6. The requirements remain identical to 2018. Some editorial clarification was added about the nail plate thickness requirement (1/16-inch minimum steel), but this was an existing requirement under 2018 that is now stated more clearly.

When to Hire a Licensed Contractor

Licensed plumbers and electricians must understand stud notching limits and apply them correctly. A licensed general contractor overseeing rough mechanical work should verify that trades are not exceeding the limits. If an inspector finds over-notched or over-bored studs, a licensed framing contractor must perform the structural repair — typically sistering a new full-depth stud alongside each damaged member. Do not close walls until the rough inspection confirms all notching is within code limits.

Common Violations Found at Inspection

• Notch depth exceeding 25% of bearing stud width — typically from a plumber running 1-inch pipe that requires a wider channel than allowed.
• Hole diameter exceeding 40% of bearing stud width — common with drain pipe penetrations through 2×4 bearing walls.
• No nail plate over a notch within 1.5 inches of the stud face — almost always found when the question is asked.
• Horizontal notches cut across multiple adjacent studs — eliminates structural continuity across an entire wall section.
• Over-notched stud discovered after drywall is installed — requires drywall removal, sistering, re-inspection, and patch repair.
• Non-bearing stud limits applied to a bearing stud — more liberal non-bearing percentages used where a bearing stud is located.
• Notch at the top or bottom of a stud combined with large hole within the same stud — combined section loss exceeds effective limits.

Wiring runs in notched studs must be protected by nail plates when any portion of the conductor is within 1.5 inches of the face of the stud. This applies to both NM cable and to conduit runs in notched studs. Nail plates for conduit runs must be the full width of the conduit diameter, not just a nominal 1.5-inch width plate intended for single-cable applications.