Bathroom waterproofing in Sydney: where to start
Bathroom waterproofing in Sydney is the hidden layer that stops water escaping from showers and floors into walls, framing and neighbouring rooms. Leaks often show up as stains, swollen skirting or mould before anyone sees a drip. Whether you are building a new bathroom or chasing a leak, the work should start with what is actually failing.
Surface staining and loose grout do not establish where a leak begins. Clarify whether the room is being rebuilt, a membrane is being installed on prepared substrates, or an existing leak is being investigated.
Signs it’s time to call a pro
- Stains or mould on walls next to the shower
- Swollen skirting boards or door frames outside the bathroom
- Loose, drummy-sounding or cracked tiles
- Grout or silicone that keeps cracking or turning black
- Water marks on the ceiling below an upstairs bathroom
What’s usually included
Every property is different, but a good quote for bathroom waterproofing should spell out items like these.
- Leak investigation or new-work scope
- Substrate condition and preparation
- Specified membrane and compatible details
- Trade interfaces and inspection records
- Testing and completion documentation
How much does it cost?
Waterproofing a bathroom typically costs about $500–$1,000, but complex jobs can reach $4,000. Per square metre, rates usually run about $35–$60.
Waterproofing membrane work only, from a national guide last updated March 2023. It does not include strip-out, tiling or repairs. Fixing an existing leak usually costs much more, because tiles and fixtures must come off and go back on.
Access to the membrane, strip-out, substrate repair and reinstatement can dominate the cost. Ask whether tiling and fixture removal are included or separate.
Indicative ranges only, compiled October 2026 from Airtasker – Waterproofing cost guide (updated Mar 2023). Your quote depends on your property and scope.
How long it takes: Applying and drying the membrane usually takes two to three days, before tiling can start.
Licences, insurance and approvals
In NSW, waterproofing is its own licence class, so waterproofing worth more than $5,000 (incl. GST) usually needs a licensed waterproofing contractor or a builder licensed for the work. The installer should give you a certificate showing the membrane meets AS 3740.
Every member of our crew has their NSW licence verified and insurance sighted before joining, and agrees to quote in writing with their licence number shown. Before you sign, confirm the licence number on the quote using the NSW Government licence check, and make sure residential work over $5,000 (including GST) has a written contract.
Have these details ready
A clear brief gets you faster, more accurate quotes.
- Leak history and affected adjacent rooms
- New build or existing bathroom
- Previous repairs
- Any strata requirements
Bathroom waterproofing: common questions
Can waterproofing be repaired without removing tiles?
The assessment must establish the defect and whether a suitable repair is possible. Do not assume a surface treatment addresses a membrane failure.
How long does bathroom waterproofing take?
The membrane itself usually takes two to three days, because most products go on in at least two coats and must dry between coats. It then needs to cure before tiling starts. Drying times depend on the product, temperature and humidity, so your installer should follow the manufacturer's data sheet rather than rush.
What does a waterproofing certificate show?
It is a document from the installer stating which areas were waterproofed, which product was used and that the work meets the relevant Australian Standard. Certifiers usually ask for it on new work, and it is useful when you sell. Keep it with the product warranty and your other home records.
Which parts of a bathroom need waterproofing?
Australian Standard AS 3740 sets different levels of protection for inside the shower, outside the shower, and around baths and basins. Generally the shower floor and walls, the floor-to-wall junctions and the areas around baths need treatment. Your installer should show you which areas they will cover before work starts.
Is a leak inspection worth paying for?
Often, yes. A specialist can use moisture meters, thermal cameras and water tests to work out whether a leak comes from the membrane, the waste, a pipe or the seals. That helps you avoid paying to rip out the wrong thing. Ask what tests are included and whether you will get a written report.
Can a leaking shower damage the rest of the house?
Yes. Water escaping from a shower can rot timber framing and floors, attract termites, encourage mould and damage the rooms or apartments next door. The longer it goes on, the bigger the repair usually becomes. If you notice signs of a leak, have the source found early.