How much does waterproofing cost per square metre?
Most residential waterproofing lands between about $35 and $120 a square metre supplied and installed, internal wet areas at the bottom, balconies and roofs in the middle, basements higher, and remedial leak repair highest per m². The levers that move the number, and why an honest quote prices by the m² and names the Standard.
Waterproofing is one of the few trades you can price by the square metre before anyone visits.
The cost is mostly the area, what is being waterproofed, the membrane system and the number of
coats. So you do not have to wait for an inspection to learn a rough number. Here is where the
figures sit, supplied and installed, in 2026.
What waterproofing costs per square metre
Cheap quote.one coat, no bond breaker, no flood test$25 to $40/m²
Internal wet areas.bathrooms and laundries to AS 3740$35 to $70/m²
Balconies and decks.above ground to AS 4654$50 to $95/m²
Roofs and podiums.exposed and buried membranes to AS 4654$60 to $120/m²
Basement and tanking.below ground, holding back water pressure$85 to $180/m²
Remedial leak repair.diagnosis, cut-out and make-good$95 to $220/m²
These are a guide only, not a quote. The cheap-quote row is in red for a reason. A number that
low usually means a single coat where the Standard needs two, no bond breaker at the junctions,
and no flood test. It is cheap because of what it leaves out, and it leaks again.
What moves the number
What is being waterproofed, and the Standard. An internal wet area to AS 3740 is the most contained job. A balcony or roof to AS 4654 adds exposure and drainage. Below-ground tanking has to hold back water pressure. Each sits higher per m² than the last, because the Standard asks more of it.
The membrane system and the number of coats. Cementitious, liquid-applied or sheet, and two coats where the Standard needs two, not one. The system is chosen for the exposure and the substrate, and the coat count is the most common place a cheap quote quietly cuts a corner.
The substrate and the strip-out. A sound, primed substrate is cheap to membrane. Grinding, crack repair, or a full strip-out of failed tiles and old membrane is a real cost before any new membrane goes down. It is itemised, never folded into a round number.
The area, by the square metre. Cost is close to linear in area, so the m² is the single biggest number on the quote. A shower recess and a roof are not the same job, which is why we price by the m² after a look, not off a guess.
The detailing complexity. Corners, the hob, the wastes, the penetrations, the upturns and the fall to drain. A fiddly recess or a balcony with a tricky fall costs more per m² than a flat, open floor, because the detailing is where the work and the risk sit.
Testing and certification. The flood test and the compliance certificate are part of doing it to the Standard, not an extra. Doing it right and proving it holds the first time costs a little more than a job that looks done and leaks again.
The honest comparison is not which quote is cheapest. It is which quotes name the same system,
the same number of coats, and the same Standard. Line those up and the gap usually explains
itself.
Why the cheapest quote is the one you pay twice
The part you pay for twice is the part you cannot see once the tiles go down. A surface seal
over a moving junction looks done on the day and fails inside a year or two. We prep the
substrate, detail the bond breakers and the upturns, apply the coats the Standard needs, then
flood-test before the tiler comes back. That costs a little more than a quick seal, and it is
the reason the wet area is still dry in ten years.
Ask this, exactly
“Can you send the quote broken down by m² and named to the Standard, with the membrane system, the number of coats, the flood test and the certificate each on their own line?”
A working waterproofer prices by the m² and names the Standard. A vague lump sum with nothing behind it hides where the corners were cut.
How we price at Sealline
Our estimator gives you a real by-the-m² range in under a minute, named to AS 3740 inside or
AS 4654 outside, before you book anyone. Then the site inspection pins the exact figure,
itemised line by line, with the system and the coats named. You can lay it next to any other
quote and see, line for line, where the difference sits.
Watch
What waterproofing really costs per square metre
A short walkthrough of the levers that move a waterproofing price, so you can read a quote and tell a fair number from a vague lump sum before you sign.
Common questions
How much does waterproofing cost per square metre?
As a guide most residential work lands between about $35 and $120 a square metre supplied and installed, membrane only. Internal wet areas sit at the lower end, balconies and roofs in the middle, and basements and below-ground tanking higher. A small leak repair reads higher per square metre because the diagnosis and the cut-out drive a fiddly job over a tiny area.
Why is one waterproofing quote half the price of another?
Usually because the cheap one is not the same job. A compliant quote names the membrane system, the number of coats, the prep, the flood test and the certificate. A surface seal or a single-coat job skips most of that, and it leaks again because it cannot handle the movement. Read the lines, not the total.
Can you give me a price without visiting?
We can give you an honest by-the-m² range on screen, and a tighter number from a photo of the stain or the area. The fixed price comes after a site inspection, because the substrate and the access change the work. We do not price waterproofing properly over the phone.