Timber notching

Timber notching is cutting a notch, or drilling a hole, in a timber framing member, usually so a service (a pipe, cable, or duct) can pass through. AS 1684.2 Section 7 sets the limits on how much you can notch or hole a stud, joist, bearer, or plate, and where on the member, before the cut weakens it below the capacity its span-table entry assumes. Cut beyond those limits and the member no longer performs to its rating, even though it still looks fine.

It is one of the most common framing defects, because the damage is usually done after the frame is up, when the plumber, electrician, or air-conditioning installer cuts services through finished framing without checking the limits. The rules exist because a notch or hole removes material from the part of the member carrying load. A notch in the wrong place, too deep, or too close to a support or an edge concentrates stress and can crack the member under load. The actual permitted dimensions depend on the member size and the location of the cut, so they have to come from AS 1684.2 Section 7 or the engineer, not a guess on site.

Engineered timber products are stricter. An I-joist, LVL, or glulam must only be cut to the manufacturer’s hole charts, never freehand, because the web and flanges do specific jobs. A nail-plated roof or floor truss must not be cut or notched at all without the truss designer’s approval, because every member is sized for the whole. Plan service routes before the frame is closed up. See AS 1684.

Also known as: Notching and holing, framing notch limits, service holes.

Category: Framing / Timber.

Related

• AS 1684 (residential timber framing)
• Timber framing basics

See also

• I-joist
• Engineered timber products
• Pine framing grades

References

• AS 1684.2 Residential timber-framed construction, Non-cyclonic areas, Standards Australia (verified 2026-05-10)
• WoodSolutions: Lightweight Timber Framing Guide (verified 2026-05-10)

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Last updated: 2026-05-30. Verified: 2026-05-10. Quarterly review for currency.