Specialist service · Melbourne-wide
Acoustic & Soundproof Caulking in Melbourne
Seal the gaps. Stop the noise. Gapless installs acoustic sealant — soundproof caulking — to wall junctions, perimeters and penetrations in apartments, offices, studios and hotels across Melbourne. It's detail work: sound finds every gap the installer missed, and with over 10 years' experience, we don't miss them.
Why sound leaks through walls — and how caulking stops it
A wall built for sound separation only performs if it's airtight. Sound travels through air, so every unsealed junction — wall-to-floor, wall-to-ceiling, around power points and pipe penetrations — is a leak. Acoustic caulking closes those paths with a dense, permanently flexible sealant that moves with the building instead of cracking. It's the cheapest part of a soundproof wall, and the part most often done badly.
Stops sound transfer cold
Perimeter and junction sealing that closes the air paths sound leaks through.
Stays flexible for good
Acoustic sealants don't harden and crack like standard fillers — the seal keeps working as the building moves.
Neat finish, no mess
Clean tooled lines ready for paint and finishing trades. We leave the site the way your builder wants it.
Answer first
What is acoustic caulking and where does it go?
Acoustic caulking is the installation of a non-hardening, permanently flexible sealant into the gaps a stud or masonry wall is built with — at floor and ceiling junctions, head of wall, perimeters, and around electrical boxes and pipe penetrations — so airborne sound can't pass through the joint instead of through the wall itself.
Every wall or floor built to separate noise — an apartment party wall, an office meeting room, a home studio, a hotel room — is only as good as its weakest gap. Framers, plasterers and services trades all leave small joints where a wall meets the structure around it: at the floor, the ceiling, the adjoining wall, and anywhere a power point, data outlet or pipe punches through the board. Acoustic sealant is the last step that closes those joints once the rest of the wall is built, and it needs to go in before the joint is covered by a skirting, a cornice, or the next layer of board. It's a small job by area — a handful of lineal metres on most rooms — but skipping it, or sealing it with the wrong product, is one of the most common reasons a wall never performs the way it was designed to.
- Non-hardening — stays permanently flexible instead of going hard and cracking like a standard gap filler.
- Dense, not just gap-filling — thick enough to block sound, not merely close a hole.
- Usually water-based acrylic or hybrid — some junctions call for a silicone-based product instead.
- Sometimes also fire rated — a handful of products do both jobs; that's confirmed on the data sheet, not by the tin colour.
Answer first
What do Rw and Rw+Ctr ratings have to do with caulking?
Rw and Rw+Ctr are the standard ratings for how much airborne sound a wall or floor blocks, used throughout the National Construction Code — Rw+Ctr in particular for walls between apartments, because it also accounts for low-frequency noise like traffic, TV bass and machinery. Those ratings only hold up on site if every junction in the wall is sealed airtight.
The numbers themselves come from an acoustic engineer's design and testing, not from the caulker on site — Gapless installs the sealant detail an acoustician or building designer has specified; we don't design, test or sign off on a wall's rating. What's well understood in the trade is that even small, unsealed gaps have a disproportionate effect on how a wall actually performs: sound takes the path of least resistance, so a hairline gap at a skirting or around a power point can undo a meaningful share of an otherwise well-built wall's rated performance. This is also where flanking paths matter — sound doesn't only travel straight through a wall, it can flank around it via a shared ceiling cavity, a party wall that stops short of a suspended ceiling, or a service riser — which is why every junction needs sealing, not just the ones that are easy to reach.
Our process
How we apply acoustic sealant
We run the same sequence on every acoustic job, whether it's one room or a whole floor of apartments:
- Scope the junctions. From an acoustician's detail, your drawings, or a walkthrough of the site, we identify every joint that needs sealing and measure it in lineal metres.
- Sequence around other trades. Sealant that needs to go between board layers, or before a skirting is fixed, has to happen at the right point in the build — not squeezed in afterwards.
- Prep the joint. Dust, off-cuts and loose material cleared out; backer rod installed where a gap is too wide or deep for sealant alone.
- Match the sealant to the junction. Non-hardening acoustic sealant, matched to the job and to the fire rating where both apply (see fire rated caulking) — mostly Pasco and APTC, with Soudal, Bostik and Sika where a job calls for them.
- Apply and tool. A continuous, gap-free bead run along the full length of the junction, tooled to a clean, consistent line.
- Check before we leave. Every run checked for missed sections before the next trade closes it up — a missed junction or the wrong sealant is much harder to fix once the board or ceiling is on.
Acoustic sealant by location
What we typically install at each junction, and why — this is the same detail we run on office meeting rooms and other commercial fit-outs as well as apartment party walls.
| Location | Sealant type | Note |
|---|---|---|
| Wall-to-floor junction | Non-hardening acoustic sealant | Carries foot traffic and building movement — usually the most heavily loaded joint on the wall. |
| Head of wall / deflection head | Acoustic sealant, sized to the deflection gap | Bead width matched to the gap so the seal survives the slab moving above it. |
| Wall-to-wall perimeter | Non-hardening acoustic sealant | Every internal corner and abutting wall, not only the external perimeter. |
| Electrical boxes & penetrations | Acoustic sealant, often with a putty pad | Putty pad on the box first, then the surrounding cut-out sealed. |
| Between plasterboard layers | Acoustic sealant, applied before the second layer | Has to go in before the joint is closed up — impossible to add once the second sheet is fixed. |
| Door frames & glazing in acoustic partitions | Acoustic sealant or an acoustic-rated seal system | Frame perimeter sealed the same as any other junction in the wall. |
Typical Melbourne market rates for this work run $8–$15 per metre, with a $250–$450 minimum call-out on small jobs — see the full caulking cost guide, or send us the junctions for a free quote.
Where we install acoustic caulking
- Apartment party walls and inter-tenancy junctions
- Office fit-outs: meeting rooms, boardrooms, consulting suites
- Hotels, studios and home theatres
- Wall perimeters: floor, ceiling and head-of-wall junctions
- Electrical boxes, pipes and service penetrations
- Combined acoustic + fire rated details (see fire rated caulking)
- More detail: why soundproof walls fail without acoustic caulking
Where we work
Areas we service for acoustic caulking
Gapless provides acoustic caulking across Greater Melbourne and regional Victoria within about 90 minutes of the CBD. We travel to the job — commercial sites, apartment buildings, warehouses and homes alike.
Melbourne CBD & inner suburbs
Melbourne, Southbank, Docklands, Richmond, Collingwood, Fitzroy, Carlton, South Yarra, Port Melbourne, St Kilda.
West & north
Footscray, Sunshine, Werribee, Point Cook, Truganina, Laverton, Melton, Essendon, Broadmeadows, Epping, Craigieburn.
East & south-east
Box Hill, Doncaster, Ringwood, Glen Waverley, Clayton, Dandenong, Cranbourne, Frankston, Moorabbin, Cheltenham.
Bayside & Mornington Peninsula
Brighton, Sandringham, Mordialloc, Mornington, Mount Eliza, Rosebud, Dromana, Hastings.
Geelong & the west
Geelong, Lara, Corio, Torquay, Ocean Grove, Bacchus Marsh, Ballan.
Not on the list?
Ask. For commercial work we regularly travel further — send the suburb through the quote form and we'll confirm.
Acoustic caulking — frequently asked questions
What is acoustic caulking?
Acoustic caulking is the sealing of gaps at wall perimeters, junctions and service penetrations with a flexible acoustic sealant. Sound travels through any air gap — even a small unsealed junction lets noise leak between rooms. Acoustic sealant stays flexible permanently so the seal doesn't crack as the building moves.
Where is acoustic sealant applied?
At the perimeter of walls (floor, ceiling and wall junctions), around electrical boxes and service penetrations, at the head of wall, and along any joint in a wall built for sound separation — apartment party walls, office meeting rooms, studios, hotel rooms and consulting rooms.
What's the difference between acoustic sealant and normal caulk?
Acoustic sealants are designed to remain permanently flexible and dense, so they keep blocking sound as the building moves. Standard gap fillers can harden and crack, opening hairline gaps that leak noise again.
How much does acoustic caulking cost?
It depends on lineal metres of joint, access, and the sealant specified. Send us the job details through the quote form and we'll price it free of charge.
Do you do small acoustic jobs, like one apartment or a home studio?
Yes. We do all jobs — from a single room to full apartment buildings. Booking is typically 1–2 weeks' notice.
Wondering what this costs? See typical Melbourne rates per metre on our caulking cost guide — or skip straight to an exact price with a free quote.
Free quote · no obligation
Get an acoustic caulking quote
Tell us the suburb and roughly what needs sealing — we'll come back with a price or a call to clarify. Quotes are free; we typically book with 1–2 weeks' notice.
- 10+ years' specialist experience
- Fully insured · SWMS & induction ready
- Pasco · APTC · Soudal · Bostik · Sika systems
Got photos or drawings? Send them on WhatsApp or call 0414 824 987.