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Framing & structure · Joist Hole & Notch Checker

Hole and notch limits for a 2x8 joist

A sawn-lumber 2x8 measures 7 1/4" deep, so the largest hole is 2 3/8" across, and it has to stay 2" clear of the top and bottom edges. Enter your own hole or notch below to check it.

Short answer
Largest hole diameter
2 3/8" (exact limit 2.416")
Hole to the top edge and to the bottom edge, at least
2"
Deepest notch in the span
1 1/8" (exact limit 1.208")
Deepest notch at the end, over the bearing
1 3/4" (exact limit 1.812")
Longest notch
2 3/8" (exact limit 2.416")

2021 IRC Section R502.8.1, for a solid sawn-lumber 2x8 that measures 7 1/4" deep, on a single span supported at both ends. Fractions are rounded down to the nearest 1/8". Notches are also barred from the middle third of the span. None of this applies to I-joists, trusses or LVL: follow the manufacturer.

Your joist

For a level floor or ceiling joist of solid sawn lumber on one simple span: a support at each end, none in between, no overhang. Not for rafters, and not for I-joists, floor trusses, LVL or glulam: the code sends those to the manufacturer's instructions or an engineer, and this tool gives no numbers for them.

How the joist is supported

Only the first case is checked: a joist that continues over a beam or wall, or cantilevers past its support, is not. "One span" is pre-selected as the common case: tap it to confirm it is yours. Until you do, the result is marked as assumed.

Lumber size

Standard dressed depths: 2×6 is 5 1/2", 2×8 is 7 1/4", 2×10 is 9 1/4", 2×12 is 11 1/4". Put a tape on yours. Old and rough-sawn lumber may be a different depth; choose Other and enter what you measure.

Thickness

By nominal size: a 4×10 is "4× or thicker" although it measures 3 1/2". The code does not say how a beam built up from several 2× pieces counts: ask your building department.

ft
Face of one support (wall, beam or hanger) to the face of the next. This is the only field in feet: 12 means 12 ft. Feet and inches like 11' 6" work too. Up to 30 ft.
in
in

How much of the joist's length rests on each support: 3 1/2" on a 2×4 wall plate, 5 1/2" on a 2×6 plate. Measure yours; the figures here are an example. The bearing sets how far the no-notch zone reaches and how long an end notch can be, so it changes a notch result (not a hole result). Enter 0 for an end held in a metal hanger. At a hanger this tool gives no deeper limit for an end notch: with no bearing to stay over, every notch is held to the span limit of one-sixth of the depth. The code says only "at the ends", so your building department may allow more.

What you want to cut
Cut
Hole
in
The size of the bit or hole saw, not the pipe. Round holes only: the code does not address square or oblong holes.
Height of the hole in the joist
in
Along the joist. Inches: 24 means 24", and 2' 6" works too. No rule depends on this unless you are also cutting a notch; then measure both from the same support, and for a notch at the end, from the support at that end.
in
Measure along the joist, rim to rim. Leave empty if this joist has no other holes or notches.
Result
Not checkedThe calculator has not run yet.

    Largest hole
    Deepest notch in the span
    Deepest notch at the end, over the bearing
    Longest notch
    No notches between (from the face of the support you measure from)
    Side view. Depth is drawn larger than length, so a round hole shows as a tall oval. Dashed lines mark the 2" bands a hole must stay out of. The shaded zone is closed to notches.

    Checked against the 2021 International Residential Code, Section R502.8.1, for one simple span of solid sawn lumber. Fractions shown are rounded down to the nearest 1/8"; the exact limit is beside each one. Where the code can be read two ways this tool takes the stricter one, so a cut it fails may still be acceptable to your building department. Your local code may be a different edition or carry amendments, and approved plans or an engineer's detail override this tool.

    Rule: 2021 IRC R502.8.1 · Tested against 22 worked examples, 4 printed in a published source · How this is worked out →

    Questions people ask

    How big of a hole can I drill in a floor joist?
    Under the 2021 IRC (R502.8.1) the hole can be up to one-third of the actual depth of a sawn-lumber joist, and its rim cannot come closer than 2" to the top or bottom edge. Rounded down to the nearest eighth, that is 2 3/8" for a 2×8, 3" for a 2×10 and 3 3/4" for a 2×12. On a 2×6 the edge rule governs and leaves room for a 1 1/2" hole.
    Can I notch a 2×10 floor joist?
    Yes, within limits. A notch can be no deeper than one-sixth of the depth (1 1/2" on a 2×10, rounded down), no longer than one-third of the depth (3"), and it cannot be in the middle third of the span. A notch at the very end of the joist, over its bearing, can be up to one-fourth of the depth (2 1/4").
    How far apart do holes in a joist have to be?
    The code says a hole cannot be closer than 2" to any other hole in the member, and where the member is notched, not closer than 2" to the notch.
    Do these rules apply to I-joists, LVL or floor trusses?
    No. Section R502.8.2 prohibits cuts, notches and holes in trusses, structural composite lumber, glued-laminated members, cross-laminated timber and I-joists unless the manufacturer’s recommendations permit them or a registered design professional has considered them in the design. Use the manufacturer’s hole chart for those products.
    What if a joist has already been cut more than the code allows?
    ICC’s CodeNotes says a structural member modified beyond what the code permits must be replaced with an unmodified member, or have a structural analysis done, usually by a registered design professional, to confirm it still has the required capacity.