What acoustic caulk does between units
Acoustic caulk closes the small gaps at the edges of a separating wall or floor, where framing meets a slab or masonry meets an adjoining wall, so airborne sound has no path around a well-built partition. Australian Caulking Experts offers it alongside fire-rated caulking, the service it sits under.
Sound insulation rules for Class 2 and 3 buildings
The NCC's Part F7 on sound transmission and insulation applies to Class 2 and 3 buildings and to Class 9c buildings. Its Deemed-to-Satisfy ratings for Class 2 and 3 buildings include:
- Walls between units: Rw + Ctr (airborne) not less than 50.
- Walls to common areas: Rw not less than 50 where a unit adjoins a plant room, lift shaft, stairway, public corridor or lobby.
- Floors between units: Rw + Ctr not less than 50 and Ln,w (impact) not more than 62.
The performance requirement for walls includes services and their penetrations, so a pipe hole through a separating wall counts against its rating.
Where acoustic caulk goes in Sydney apartment buildings
Specification 28 lists forms of construction deemed to reach those ratings, provided they are installed as it describes. Its joint rules are:
- perimeter framing of timber or steel walls bedded in resilient compound, or caulked so there are no voids between the framing and the adjoining structure
- masonry laid with all joints filled solid, including those to adjoining construction
- joints between concrete slabs or panels and adjoining construction filled solid
- joints between sheets, and between sheets and adjoining construction, taped and filled solid
Part F7 also requires a separating wall to run to the underside of the floor or roof above, or to a ceiling providing the required insulation, so acoustic caulk belongs at the head of the wall as well as its ends.
Sealing for sound and fire in one pass
Where a wall between units also carries a fire resistance level (FRL), a service through it answers to both parts of the code: Part F7 for sound, and the fire provisions for service penetrations. The fire side calls for a system matching a tested prototype, so the product in a shared junction has to meet both purposes and be installed as its manufacturer specifies.
Pricing acoustic caulk with the fire scope lets each junction be sealed for both purposes in one sequence instead of two visits. Fire-only detail is on the commercial fire-rated and residential fire-rated sealing pages. Background on test ratings is in the post on acoustic rating compliance.
Quoting acoustic and fire scopes together
Send plans or takeoffs with the acoustic and fire-rated walls marked, or arrange a walk-through. Multi-residential packages are usually measured and priced per lineal metre, and large developments can get a tailored metre rate set by volume and access, from a 10m boutique fit-out to 3,000m across an apartment development. Expect a quote response within 24 hours.
Frequently asked questions
Is acoustic caulk the same product as fire-rated sealant?
Not necessarily. An acoustic sealant is chosen to stay flexible and close the junction airtight, while a fire-rated sealant has to form part of a system tested under AS 1530.4 for the wall or floor it sits in. Some products are made for both jobs, but only the manufacturer's test data shows whether one product covers both at a given joint, so the choice is made junction by junction.
How is the sound rating of a finished wall checked?
Part F7 offers a verification method that measures the finished wall in place: a wall between units passes when the measured DnT,w + Ctr is not less than 45, determined under AS/NZS ISO 717.1. The Deemed-to-Satisfy route instead relies on the laboratory ratings of listed or tested forms of construction, installed as described. The project's design documents say which route applies to a given wall.
Is acoustic caulk work available in Rouse Hill?
Yes. Australian Caulking Experts works across all areas of Sydney, and Rouse Hill falls within that coverage. The Rouse Hill caulking page lists every service offered there. Apartment projects in the suburb are scoped and priced as anywhere else in Sydney, with acoustic and fire-rated junctions measured together.