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HardieSmart® Intertenancy Wall System

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Fire, Sound and Floor Space, Solved Together

The wall between two attached dwellings has to do more work than almost any other wall in the building. It carries the fire separation requirement between sole occupancy units. It carries the acoustic requirement that determines whether residents can hear their neighbour’s television. And every millimetre of its thickness is floor area that neither dwelling gets to use, which makes wall thickness a genuine commercial consideration on any row housing or attached dwelling project.

The HardieSmart® Intertenancy Wall System is engineered to resolve all three demands in a single tested assembly: a twin 90mm timber frame separated by a 30mm cavity, insulated with 60mm HardieFire™ insulation on both frames, and lined with 9mm Villaboard™ on both sides. Tested to FRL 60/60/60 minutes with acoustic performance independently assessed by Renzo Tonin Acoustics, and up to 18% more compact than a traditional common plasterboard shaftliner wall system, which in a row housing development adds up to real, saleable floor area across every dwelling.

60/60/60

Fire Resistance Level (minutes)

18%

More compact than traditional shaftliner wall systems

30mm

Cavity separation between twin frames, reduces sound transmission

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Technical Specifications

Design guide

Fire Resistance Level

60/60/60 minutes

Suitable building class

Class 1 and Class 10a timber-framed buildings, attached dwellings, row housing

Frame configuration

Twin 90mm timber frames with 30mm cavity separation

Insulation

60mm HardieFire™ mineral wool insulation on both frames within stud bays

Internal lining

9mm Villaboard™ lining on both sides (alternative configurations available)

Acoustic testing

Independently assessed by Renzo Tonin Acoustics Pty Ltd

Compactness advantage

Up to 18% more compact than traditional common plasterboard shaft-liner wall systems

Services allowance

System configuration allows for services (electrical, plumbing) within the cavity while maintaining FRL

Assessment

CSIRO Division of Building Construction and Engineering, in accordance with AS 1530.4

Bracing capacity

Typically 4 kN/m for plain timber framing and standard fixings, 6–10 kN/m with alternative fixings and 12mm anchor rods

Applications

Separating walls in row housing, townhouses, dual occupancy and attached Class 1 dwellings

How the System Is Built

The system uses two independent 90mm timber frames, physically separated by a 30mm cavity. This structural separation is the key to the system’s acoustic performance; a continuous frame connection between two dwellings acts as a flanking path that transmits sound directly through the structure, no matter how good the insulation and lining are. Breaking that structural connection with a genuine cavity gap is what allows the twin-frame approach to achieve genuinely tested acoustic performance rather than a theoretical rating.
Each frame is insulated with 60mm HardieFire™ mineral wool insulation within the stud bays, and both frames are lined with 9mm Villaboard™, James Hardie’s high-density wet-area-grade lining, on both faces. Alternative lining configurations are available; refer to the current design guide for options where 9mm Villaboard™ on both sides isn’t the specified finish.

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The Floor Area Case for Intertenancy

18% more compact than shaftliner

Traditional common wall systems using plasterboard shaftliner construction require greater overall thickness to achieve equivalent fire and acoustic performance. At up to 18% more compact, the Intertenancy system recovers usable floor area on both sides of the wall, across a full row housing development, that adds up to a meaningful yield improvement.

Services within the cavity

The 30mm cavity separation between the twin frames isn't just an acoustic break; it can also accommodate services running vertically between floors without compromising the fire rating, provided penetrations are detailed and fire-stopped correctly per the design guide.

Genuinely tested acoustic performance

Acoustic performance for the Intertenancy system has been independently assessed by Renzo Tonin Acoustics, a specialist acoustic engineering consultancy, rather than estimated from component data. For projects where acoustic compliance documentation needs to stand up to certifier scrutiny, tested data carries more weight than calculated estimates.

Single tested assembly for fire and acoustic

Rather than specifying separate fire and acoustic solutions and hoping they work together, the Intertenancy system is tested as one complete assembly for both performance requirements simultaneously, reducing the compliance risk that comes from combining independently tested components.

Featured Projects with HardieSmart® Intertenancy Wall System

Bacchus Marsh Grammar Woodlea Project

Mernda Ambulance Station Cladding Project

The Wickham Duplex Residential Project

Frequently Asked Questions

Why does the Intertenancy system use twin frames instead of a single shared frame?
A single continuous frame connecting two dwellings creates a structural flanking path that transmits sound directly through the timber, regardless of how well the wall is insulated and lined. The Intertenancy system’s twin 90 mm frames, physically separated by a 30 mm cavity, break that structural connection, which is what allows the system to achieve genuinely tested acoustic performance rather than a theoretical rating based on insulation and lining alone.
The HardieSmart® Intertenancy Wall System is up to 18% more compact than traditional common plasterboard shaftliner wall systems used for the same fire and acoustic separation function. In a row housing or townhouse development, that compactness translates into additional usable floor area on both sides of the wall, a meaningful yield benefit across a full development.
The 30mm cavity between the twin frames can accommodate services, but penetrations must be detailed and fire-stopped correctly to maintain the tested FRL. Refer to the current HardieSmart® Intertenancy design guide for the specific penetration and service detailing requirements; incorrect service penetrations are one of the most common ways a tested fire-rated wall assembly is compromised on site.
Yes. Acoustic performance for HardieSmart® Wall System variations, including Intertenancy, was assessed by Renzo Tonin Acoustics Pty Ltd, an independent acoustic engineering consultancy. This is distinct from calculated or estimated acoustic performance and provides genuine tested data for certification purposes. Refer to James Hardie’s Fire and Acoustic-Rated Walls Application Guide and the NCC for the relevant acoustic compliance framework.