Internal Wet Area Waterproofing
A wet area is only as good as the membrane under the tiles, and the membrane is only as good as the detailing at the junctions. We waterproof bathrooms, ensuites and laundries to AS 3740, with bond breakers at the corners, the upturns to height and a fall to the waste, then we flood-test it and hand over the certificate so the tiler can come back and the job signs off.
What this job includes.
- ✓Bathrooms, ensuites and laundries to AS 3740, new and renovation
- ✓Bond breakers at the junctions, upturns to height, falls to the waste
- ✓The membrane system and the number of coats named on the quote
- ✓Flood-tested before the tiler returns, then certified
- ✓Compliance certificate and 10-year membrane warranty handed over
What AS 3740 actually asks of a wet area
A wet area built to AS 3740 is not a coat of paint on a floor. The Standard sets where the membrane has to go, how far up the wall it has to climb at every junction, what the substrate has to do before the membrane goes down, and the test that proves it holds before the tiles ever come back.
Three things decide whether the job lasts ten years or one: the substrate is ground, primed and dry; the bond breakers and the upturns are detailed at every wall-to-floor and wall-to-wall junction; and the membrane is the right system for the area, applied in the coats the Standard names, each cured to hold-down before the next.
What we do on an AS 3740 job
- Diagnose and prep the substrate. For a renovation we strip back to the substrate, check the falls to the waste with a level, grind out cracks and prime the surface so the membrane has something to grip. A new bathroom starts a step earlier with the falls set right in the screed.
- Detail the junctions. Bond breakers at every wall-to-floor and wall-to-wall corner, the upturns taken to the height AS 3740 requires for the shower, the splash zones and the rest of the wet area. The waste sealed in, the penetrations flashed.
- Apply the membrane system. A cementitious or liquid-applied system named on the quote, in the number of coats the Standard requires, each cured to the manufacturer’s hold-down. We tell you which system suits the area, and why.
- Flood-test and certify. The wastes plugged and the wet area flooded for the period the Standard names, the membrane proven to hold, then the AS 3740 compliance certificate issued and handed over with the membrane workmanship warranty in writing.
What a Sealline AS 3740 quote names
The Standard. The membrane system and the product. The number of coats. The substrate prep and any strip-out. The flood test and the compliance certificate. The ten-year membrane workmanship warranty alongside the manufacturer system warranty. Every line on the page, before any work starts.
The cheap quote that skips one of these usually skips three: no Standard named, no system, no flood test. The job looks done the same afternoon and leaks back through the ceiling a year later. We will not write a quote that omits the lines that protect you.
Priced by the m², itemised line by line.
The area by the m², the Standard it meets, AS 3740 inside or AS 4654 outside, the membrane system and the product, the number of coats, the prep and any strip-out, the flood test and the certificate. Not one round number for the waterproofing.
- 1 The area, by the square metre. The price broken down by the m² and the area, not one round number for "the waterproofing". A shower recess, a bathroom and a balcony are different jobs, and the quote should show it.
- 2 The Standard it has to meet. AS 3740 inside a wet area, or AS 4654 outside on a balcony, deck or roof, named on the page. The Standard is what sets the coats and the detailing, so naming it is the honest part of the quote.
- 3 The membrane system and product. Cementitious, liquid-applied or sheet, and the actual product named, not "we will seal it". The system is chosen for the exposure and the substrate, and you should see which one you are paying for.
- 4 The number of coats. How many coats, because the most common cheap shortcut is one coat where the Standard needs two. It is invisible the moment the tiles go down, so it belongs on the quote.
- 5 Prep and any strip-out. The substrate prep, and the strip-out of failed tiles or membrane where it is needed, as their own line. Prep is a real cost before any membrane goes down, never folded into a round number.
- 6 The flood test and certificate. The flood test that proves the membrane holds water, and the compliance certificate a licensed waterproofer issues. The test is the difference between it looks done and it is proven.
- 7 The membrane warranty. The 10-year membrane workmanship warranty in writing, alongside the manufacturer system warranty. The cover a cheap operator will not put on paper, because they cannot stand behind a rushed job.
What happens, step by step.
Inspect and diagnose
We look at the job and, for a leak, trace where the water is actually getting in, because the stain is rarely under the source. We check the falls, the substrate and the detailing before we quote anything.
Strip out and prepare
Where the old membrane or tiles have failed, we strip them back. Then we grind, repair cracks, and prime the substrate, because a membrane is only as good as what it is stuck to.
Detail the junctions
Bond breakers at the wall-to-floor corners, the upturns to height, the penetrations and wastes sealed in, and the fall to the drain set right. The junctions are where a wet area moves and where it leaks.
Apply the coats
The membrane system to AS 3740 or AS 4654, the number of coats the Standard needs, each cured before the next. We name the system and the coats on the quote, and apply exactly that.
Flood test
We plug the wastes, flood the area, and leave it to confirm the membrane holds water before anything goes on top. The test is the proof, and it is a real step, not an optional extra.
Certify and hand over
We issue the compliance certificate for the work and hand over the membrane warranty in writing, so your builder, certifier and insurer have the paperwork the job needs.
The paperwork behind the price.
Public liability to $20M, and a 10-year membrane workmanship, all in writing, all on request.
We hold a QBCC licence for waterproofing in Queensland, the licence that lets us flood-test and issue the compliance certificate, and we carry public liability insurance, so you are covered on site. The guarantee is a 10-year written warranty on the membrane workmanship, the part that fails first when a job is rushed, alongside the manufacturer system warranty on the accredited membrane we install to AS 3740 or AS 4654. All in writing, with exclusions named.
Internal Wet Area Waterproofing jobs we’ve done.
Before 
After Internal Wet Area Waterproofing: common questions.
What does AS 3740 actually require in a bathroom?
Why does a shower recess cost more per m² than a laundry floor?
Do I need the waterproofing certified for my bathroom renovation?
Can you waterproof around an existing bath, or does it have to come out?
Get a free, itemised quote you can actually read.
Tell us what you need. We’ll book a walkthrough and send a quote with the work itemised, not just a number.