Waterproofing is the highest-consequence, lowest-visibility trade on a Melbourne renovation. When it fails, it fails behind tiles, behind cladding, above ceilings. Most owners choose on price because they have no easy way to tell one waterproofer from another. This guide gives you nine specific questions to ask on the phone that will separate a specialist from a chancer in about five minutes.
The nine questions to ask before you sign a waterproofing quote
1. Are you a VBA-registered waterproofer? (Ask for the licence number and check it.) 2. What membrane system are you specifying and why? A specialist will name the product and defend the choice against alternatives. 3. What Australian Standard governs my job? (AS 3740 for internal wet areas, AS 4654 for external.) 4. Will I receive a compliance certificate in my name on completion?
5. What is your public liability cover? ($20 million is standard for commercial work.) 6. Do you carry manufacturer accreditation from the membrane supplier? (Ardex, Sika and Gripset all publish approved-installer lists.) 7. Can I see three recent jobs of this type? 8. What is your warranty and what does it cover? 9. Who does the work — your crew or a subcontractor?
Red flags in a quote
A quote that does not name the membrane product. A quote that does not reference the Australian Standard. A quote without a compliance certificate line item. A price that is 40% under the others — someone is skipping a coat, an upturn, or a bond breaker. Cash-only pressure. No physical business address.
Where to check credentials in Melbourne
The Victorian Building Authority publishes a public register of licensed waterproofers at vba.vic.gov.au. Google reviews with photo evidence matter more than star counts alone — look for reviewers who describe the specific work done, not generic five-star single sentences. Instagram grids of completed jobs (before, membrane detail, tile finish) are a strong signal that a business does its own work.
Frequently asked
Is the cheapest waterproofing quote ever the right one?+
Almost never on a wet area or balcony. The cost to rectify a failed membrane is 5–10× the original install. Choose on credentials and specification, then compare price.
How long should waterproofing last?+
A correctly installed internal membrane should last the life of the tile finish (20+ years). A trafficable balcony membrane is warranted for 10 years and typically lasts 15–20 with normal maintenance.