Where do you notch joists?
Mia Moss
Published May 09, 2026
- Notches should only be made in the top edge of the joist.
- Notches should be no deeper than 0.125 times the depth of the joist.
- Notches should be no closer to the structure supporting them than 0.07 times the span of the joist.
- The notches should be no further away than 0.25 (¼) times the span.
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Also know, how much of a joist can be notched?
The maximum depth of a notch at the end of a joist (where it rests on a wall or beam) can't exceed one-quarter of the joist depth. Maximum notch depth in the outer third of a joist is one-sixth of the joist depth. Limit the length of notches to one-third of the joist depth. No notching in the middle third of a joist.
One may also ask, where can I drill holes in joists? area in the middle of the 2×10 joist where the hole can go. Although notches aren't allowed in the center third of a joist's length, you can drill holes anywhere along the length of the floor joist in that 5 1⁄4-in. area provided there are no other holes in the joist or notches along its top or bottom.
Likewise, can you notch floor joists for plumbing?
Tradespeople often need to cut notches or holes in floor and ceiling joists to run pipes, ductwork, or wires. Sometimes joists are notched at the end where they bear on a wall or sill. If the cut-outs are too large or in the wrong location, the joist can be weakened and unable to support the load it was designed for.
Is it OK to drill through floor joists?
The hole cannot be larger than one-third the depth of the joist, so the maximum hole size for a 2×12 joist (actual size 1-1/2 x 11-1/4 in.) is 3-3/4 in. You can drill the holes anywhere along the length of the joist (first photo). If you have manufactured I-joists, you can drill holes up to 1-1/2 in.
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