The building code limits bored holes by the lumber's actual size, not its nominal size. A 2x4 is really 3-1/2" deep, so the limit for a hole in a bearing-wall stud is 1.40".
A 2x6 is really 5-1/2" deep, so its limits are bigger, but pipe has the same trap the other way round: the hole saw is bigger than the pipe's name. The tables below put the two together.
Studs (IRC R602.6)
- A bored hole can be up to 60% of the stud's depth, with its edge at least 5/8" from the edge of the stud, and not in the same section as a cut or notch.
- In an exterior wall or bearing partition, a hole over 40% means the stud has to be doubled, and no more than two successive doubled studs can be bored that way.
- So, in practice: 40% for a single stud in a bearing or exterior wall, 60% in a non-bearing partition or a doubled stud.
Joists (IRC R502.8.1)
- A bored hole can be up to one-third of the joist's depth.
- Keep it at least 2" from the top and bottom edges, and 2" from any other hole or notch.
- I-joists, LVL and other engineered lumber follow the maker's own hole chart, not these rules.
Top plates (IRC R602.6.1)
Where piping in an exterior or bearing wall cuts the top plate by more than 50% of its width, fasten a galvanized steel tie at least 0.054" (16 ga) thick and 1-1/2" wide across the opening, with eight 10d nails each side and extending at least 6" past it. Not needed if that side of the wall is covered in wood structural panel sheathing.
These are the 2021 and 2024 IRC rules (the 2021 edition changed “width” to “depth”). Your area may use another edition or local amendments, so check with your building department. Stud shoes, where approved, can allow more.
| Lumber | Actual depth | Bearing-wall stud (40%) | Doubled or non-bearing stud (60%) | Joist (1/3) |
|---|---|---|---|---|
| 2x4 stud | 3-1/2" | 1.40" | 2.10" | n/a |
| 2x6 stud | 5-1/2" | 2.20" | 3.30" | n/a |
| 2x6 joist | 5-1/2" | n/a | n/a | 1.83" |
| 2x8 joist | 7-1/4" | n/a | n/a | 2.41" |
| 2x10 joist | 9-1/4" | n/a | n/a | 3.08" |
| 2x12 joist | 11-1/4" | n/a | n/a | 3.75" |
| Pipe | Hole saw | 2x4 bearing (1.40") | 2x4 non-bearing (2.10") | 2x6 bearing (2.20") | 2x6 non-bearing (3.30") |
|---|---|---|---|---|---|
| 1-1/4" PVC / ABS pipe | 1-13/16" | No | Yes | Yes | Yes |
| 1-1/2" PVC / ABS pipe | 2-1/16" | No | Yes | Yes | Yes |
| 2" PVC / ABS pipe | 2-1/2" | No | No | No | Yes |
| 3" PVC / ABS pipe | 3-5/8" | No | No | No | No |
| 1/2" Copper / PEX | 3/4" | Yes | Yes | Yes | Yes |
| 3/4" Copper / PEX | 1" | Yes | Yes | Yes | Yes |
| 1" Copper / PEX | 1-5/16" | Yes | Yes | Yes | Yes |
| 1/2" EMT conduit | 7/8" | Yes | Yes | Yes | Yes |
| 3/4" EMT conduit | 1-1/16" | Yes | Yes | Yes | Yes |
| 1" EMT conduit | 1-5/16" | Yes | Yes | Yes | Yes |
“Exact fit only”: the easy-clearance saw is over the limit but the exact-fit saw isn’t. Limits rounded down to the hundredth. Holes centered, so the 5/8" edge distance holds in every case shown.
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