Kitchen sink drain rough-in
What's wrong here?
- The exterior-wall studs are notched about 2 in. deep, more than 25 percent of their 5-1/2 in. width
- Steel protection plates are not allowed over a notch; the stud must be left exposed for inspection
- Nothing. A notch up to 40 percent of the stud width is allowed
- A drain may not run horizontally through wall studs; it must drop below the floor
Show the answer and the code reference
The answer
The studs in this exterior wall are notched about 2 in. deep for the drain, roughly 36 percent of their 5-1/2 in. width, and R602.6 limits notches in exterior-wall and bearing-wall studs to 25 percent.
Correct choice: 1. The exterior-wall studs are notched about 2 in. deep, more than 25 percent of their 5-1/2 in. width
Exterior wall studs carry the roof and floor loads and resist wind pushing on the wall, so R602.6 limits a notch to 25 percent of the stud width, which is 1-3/8 in. on a 2x6. The tape shows these notches running back to the 2 in. mark, about 36 percent. The 40 percent notch allowance in the same section is only for studs in nonbearing partitions, so it does not help here. The steel plates protect the pipe from fasteners but do not restore any strength.
How to fix it
Pull the drain, then replace or reinforce the damaged studs (the R602.6 exception allows approved stud shoes installed per the manufacturer). Rerun the drain through bored holes. A 2x6 stud can take a hole up to 40 percent of its width (about 2-3/16 in.) without doubling, which is enough for 1-1/2 in. pipe, as long as the hole edge stays at least 5/8 in. from the stud edge.
Code reference
IRC 2018 R602.6 — Drilling and notching—studs
Item 1: a stud in an exterior wall or bearing partition may be cut or notched to a depth of not more than 25 percent of its width; studs in nonbearing partitions may be notched up to 40 percent of a single stud width. Item 2 covers bored holes. Approved stud shoes installed per the manufacturer are permitted as an exception.
Drills citing R602.6
2024 IRC:changed: The 2024 IRC rewords R602.6 as prohibitions and measures notches and holes against the stud 'depth' rather than 'width', and fixes the hole edge distance to read 'not less than 5/8 in.' The limits used here are unchanged: 25 percent notch in exterior and bearing walls, 40 percent in nonbearing partitions. Based on published 2024 text seen in search results, not checked against the printed code. Confidence: medium
Minnesota
Minnesota adopts the 2018 IRC with Minnesota amendments as the Minnesota Residential Code (Minn. Rules ch. 1309). No Minnesota amendment to R602.6 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
- Steel protection plates are not allowed over a notch; the stud must be left exposed for inspection. The plates belong there: the plumbing code calls for steel shield plates where a pipe sits close to the stud edge, to stop drywall screws. They are not the problem, but they also add no strength back to the stud.
- Nothing. A notch up to 40 percent of the stud width is allowed. The 40 percent notch limit applies only to studs in nonbearing interior partitions. Studs in exterior walls and bearing partitions are limited to 25 percent (R602.6, item 1).
- A drain may not run horizontally through wall studs; it must drop below the floor. Horizontal drains through studs are common and allowed. The framing rules only limit how much wood is removed: bore holes up to 60 percent (doubling the stud over 40 percent in an exterior wall) or notch up to 25 percent.