Frequently asked questions

Successive state defect surveys (NSW, VIC, QLD) put waterproofing failures at the top of every list — usually 25-35% of all reported defects. The reasons are almost never the membrane material itself:

• Detailing — corners, penetrations, hob junctions, drainage outlets done sloppily.
• Substrate prep — membrane applied to a substrate that wasn't primed, or wasn't clean, or had moisture in it.
• Specification — wrong membrane type for the conditions (e.g. an internal-grade membrane on an exposed balcony).
• Application thickness — membrane applied too thin, often because the applicator was paid per square metre.

The membranes themselves are fine. The execution is where most failures happen.

AS 3740 is the Australian Standard for waterproofing of domestic wet areas. The key requirements:

• Showers: entire floor + walls within shower up to 1800mm
• Bathrooms (outside the shower): floor + perimeter walls to 150mm
• Hobs and step-downs: 150mm up the inside of the hob, full thickness across the top
• Laundries below ground level: entire floor
• Toilets: floor + perimeter walls to 150mm
• Penetrations (waste outlets, taps, pipes) must be sealed with proprietary collars or membrane-compatible sealants
• Movement joints must be bridged with bond-breaker tape

Compliance is mandatory under the National Construction Code (NCC). For renovations, the work must comply with AS 3740 even where the original installation predated the Standard.

The major categories:

• Polyurethane (PU) — liquid applied. The most common for wet areas and balconies. Cures to a tough, elastic membrane that handles substrate movement. Around 1.5mm thick when applied in 2-3 coats.
• Acrylic — liquid applied. Cheaper than PU, water-based, easier to apply, but lower stretch and lower water resistance. Acceptable for internal wet areas only — never use on a balcony.
• Cementitious crystalline. Penetrates into the concrete itself, doesn't form a surface film. Used for tanking concrete basements, retaining walls, water tanks. Tolerates negative-side water pressure.
• Sheet membrane (PVC, TPO, EPDM). Pre-manufactured rolls heat-welded at the seams. Excellent for large flat areas and roofs. Faster to install but detailing at penetrations needs more skill.
• Bitumen (torch-on or self-adhesive sheet). Heavy-duty, used for basements and roof decks. Long-life, but heavier installation and needs protection from UV.

The right choice depends on the substrate, the exposure, the movement, and what's going on top.

Good waterproofing, properly applied, should last 15-25 years for wet areas and 15-20 years for exposed balconies. Major membrane manufacturers offer 10-25 year product warranties on their systems when applied by certified applicators.

Bad waterproofing fails inside 5 years — sometimes inside one. The gap between "good" and "bad" is entirely in workmanship and specification; the materials themselves are reliable.

Tiles are not waterproofing. Grout is not waterproofing. The membrane underneath is, and when it fails, water gets into the substrate before any visible damage. Most "shower leaks" are membrane failures at one of three places:

• Corner cracking — the most common cause. The membrane stretches at the floor-wall corner with building movement and eventually splits.
• Penetration seals — the seal around the waste outlet or shower mixer body. Wear and movement.
• Hob failure — the lip at the front of the shower. Water sits, membrane degrades.

The honest answer about repair: removing the membrane means removing the tiles. There's no shortcut. We can sometimes apply a surface treatment over compromised tiles as a stop-gap, but the proper fix is a re-do.

Yes, in some circumstances. Specialist "overlay" or "topical" waterproofing products are designed for application over existing tiled surfaces, primarily as a remedial measure when complete strip-back isn't practical. They work, but with caveats:

• Substrate movement must be minimal — tiles can't be loose or drumming
• The finished surface will be slightly different in appearance and slip rating
• Generally a 5-10 year solution rather than 20+

For a strata bathroom where stripping isn't feasible, or as a stop-gap before a full renovation, it can be a sensible call. For a permanent fix, strip and re-do.

Balconies are the second most common source of waterproofing claims after showers, and for a similar reason: detailing at the most demanding points.

• Door threshold detail — where the membrane runs up against the door frame. Common to be undercut, water tracks in.
• Drainage outlet — the floor drain. Often installed before the membrane and not flanged properly. Water finds the gap.
• Hob upturn — the lip at the balcony edge. Falls must direct water away from the building; if the slope is wrong, water ponds against the wall junction.
• UV degradation — bitumen membranes left exposed to sun fail in 5-7 years rather than 20.

A properly detailed balcony lasts 20 years. A poorly detailed one fails in 3-5.

In Queensland, Form 16 is a certificate of inspection issued by a licensed inspector confirming that building work has been carried out in compliance with the relevant Australian Standard. For waterproofing, this is the document that proves AS 3740 was met.

For new construction and substantial renovations the Form 16 is generally required by the building certifier. For minor work it may not be strictly required, but it's worth having — it's the document that protects you if you ever sell, have an insurance claim, or get into a dispute with a future builder. Other states have equivalent compliance certificates.

We provide compliance documentation as standard.

Flood testing is the only way to confirm a wet area membrane is actually watertight before tiling closes it in. The process: plug the floor waste, fill the area with water to the height of the hob (typically 25-50mm), wait 24 hours, check for any leakage downstairs or any drop in water level.

It is standard practice for all our shower and bathroom installations. The cost is the inconvenience of waiting 24 hours, but the catch is real — about 1 in 30 jobs reveals a defect at flood test, which we then fix before tiling. Without the test, that 1 in 30 becomes a customer call-back 6 months later.

Yes. Flood testing isn't strictly mandatory under the Standards (which is a notable gap), but every major manufacturer recommends it and most state inspectors look for evidence of it. The argument "we don't need to" usually translates to "we don't want the 24-hour delay".

If you're paying for waterproofing work, the additional cost of a flood test on top is negligible — and it removes the largest single failure mode (membrane defect detected late) from your future.

Three layers:

• Statutory warranty under your state's building act. For wet areas this is typically 1-2 years (non-structural) and 6 years for structural defects. This applies regardless of what's in writing.
• Manufacturer warranty on the membrane itself, typically 10-25 years when applied by a certified applicator (which we are for the major brands).
• Our workmanship warranty: 10 years on wet areas and balconies, 2 years on remedial overlay work. Matches the manufacturer's product warranty wherever possible.

What's not covered: damage caused by subsequent building work (someone else drilling through the membrane), damage from substrate movement we couldn't anticipate, or end-of-life membrane degradation.

Yes. We hold the appropriate state waterproofing licence (mandatory in QLD over a low threshold, recommended in all other states). We're certified applicators for the major membrane manufacturers, which gives access to their extended manufacturer warranties. We carry public liability insurance and contract works insurance on every job. Happy to show certificates — if a contractor won't, that is a red flag.