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Inter-tenancy wall

An inter-tenancy wall separates two dwellings and must meet an NCC acoustic target (Rw+Ctr 50+) and often a fire rating, via a tested framing, lining and batt system.

By Dan Waring. Last updated 1 June 2026. Verified 1 June 2026.

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An inter-tenancy wall is a wall separating two separate dwellings, Class 1b terraces, Class 2 apartments, that must meet an NCC acoustic target (Rw + Ctr of 50 or more) and often a fire rating as well. It is achieved with a tested system of framing, lining, and acoustic batt, not just a thicker wall.

It does two jobs at once:

  • Acoustic separation: the NCC sets a minimum airborne sound rating for walls between dwellings, expressed as Rw + Ctr (the Ctr term weights it toward low-frequency noise like home theatres and traffic). For habitable-to-habitable separation the figure is at least 50, with stricter treatment where the wall adjoins a bathroom or laundry on the other side.
  • Fire separation: between sole-occupancy units the wall usually also needs a fire resistance level (so it has integrity and the other FRL criteria), and it must continue through to the underside of the roof or floor above so fire and sound cannot pass over the top.

The performance comes from a tested system: a specific framing type (often a discontinuous or double stud, or a staggered stud), the right number and type of plasterboard layers, acoustic batt in the cavity, and resilient mounts or isolation, all built exactly as tested.

For a builder the practical points are to build the inter-tenancy wall strictly to the tested system (substituting a lining, leaving out the batt, or rigidly bridging the two leaves quietly destroys the acoustic rating), to seal every penetration and the wall-to-floor and wall-to-roof junctions (flanking paths and gaps are where the rating is lost), and to carry the wall full height to the structure above. A failed inter-tenancy wall is expensive and disruptive to fix after lining, so get the system and the junctions right the first time.

Also known as: Party wall, separating wall, tenancy wall.

Category: Acoustics and fire / Separation.

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Last updated: 2026-06-01. Verified: 2026-06-01. Quarterly review for currency.

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