FAQ's

Waterproofing is the process of preventing water penetration into buildings and structures. It protects against structural damage, mould growth, substrate deterioration, and costly repairs. In Australia, compliant waterproofing is critical for wet areas, balconies, rooftops, basements, and external decks under the NCC and Australian Standards.

A properly installed waterproofing system can last anywhere from 10–25 years depending on:

• Product type
• UV exposure
• Substrate movement
• Drainage quality
• Installation workmanship
• Maintenance practices

Most failures are caused by poor preparation or incorrect installation rather than membrane quality alone.

The most common waterproofed areas include:

• Bathrooms and showers
• Balconies and terraces
• Rooftops
• Planter boxes
• Basements
• Retaining walls
• Swimming pools
• External podiums
• Laundries

Australian Standards such as AS 3740 and AS 4654 define requirements for different applications.

• Waterproof systems completely prevent water penetration under specified conditions.
• Water-resistant materials only resist moisture to a limited extent and are not suitable for constant or hydrostatic exposure.

This distinction is important when selecting membranes, sealants, and tile systems.

The most common causes are:

• Poor surface preparation
• Incorrect membrane thickness
• Lack of movement joints
• Bad detailing around penetrations
• Incompatible products
• Structural movement/cracking
• UV degradation
• Poor drainage
• Non-compliant installation

Many failures occur at junctions, corners, and terminations rather than open membrane areas.

Membrane thickness depends on the product system and manufacturer specifications. Wet film thickness and dry film thickness (DFT) are critical for performance.
Typical liquid-applied membranes require:

• Multiple coats (usually two coats)
• Minimum DFT compliance
• Reinforcing or bond breakers at joints and corners

Insufficient thickness is one of the biggest industry defects.

Yes. In Australia, waterproofing systems should comply with:

• NCC requirements
• Relevant Australian Standards
• CodeMark or equivalent testing/certification where applicable

Many builders and certifiers require documented compliance evidence.

Signs of failure include:

• Water stains
• Efflorescence
• Bubbling paint
• Mould growth
• Drummy tiles
• Cracked grout
• Damp smells
• Leaks below balconies or wet areas
• Concrete spalling

In many cases, visible leaks appear long after the membrane initially failed.

Positive waterproofing is applied to the side of the structure exposed to water pressure (the “wet side”). This is the preferred method because it prevents water from entering the substrate in the first place.
Examples:

• Balcony membranes
• Rooftop systems
• External basement tanking

Negative waterproofing is applied to the opposite side after water has already penetrated the substrate. It is commonly used for remedial works where external access is impossible.
Examples:

• Internal basement leak repairs
• Lift pits
• Retaining walls

Positive-side waterproofing generally offers superior long-term protection.

Flood testing requirements vary depending on:

• Project specifications
• Building certifier requirements
• State regulations
• Builder QA procedures

Under Australian Standards and best practice:

• Shower bases and wet areas are commonly flood tested
• Balconies and rooftops may undergo pond testing
• Commercial projects often require documented testing

Typical testing periods range from 12–24 hours.

There is no single “best” membrane – the correct system depends on the application.

Polyurethane and Hybrid Polyurethane Membranes
Best for:

• Balconies
• External decks
• Exposed areas

Advantages:

• Highly flexible
• Durable
• Excellent UV/weather resistance (with suitable topcoat)

Acrylic and Hybrid Acrylic Membranes

Best for:

• Internal wet areas
• Non-immersed applications

Advantages:

• Easy application
• Cost effective
• Low VOC options available

Cementitious Membranes

Best for:

• Pools (Under tile)
• Basements
• Retaining walls
• Balconies (Under tile)

Advantages:

• Excellent bonding to concrete
• Some products handle negative pressure
• Won’t re-emulsify  

Sheet Membranes

Best for:

• Commercial projects
• High-risk waterproofing
• Podiums, roofs, basements, planter boxes

Advantages:

• Consistent thickness
• Factory-controlled quality
• Excellent long-term durability
• Low maintenance

System selection should consider:

• UV exposure
• Movement
• Immersion
• Traffic
• Drainage
• Substrate type
• Project warranty requirements

Key Australian Standards include:

Internal Wet Areas – AS 3740

Covers waterproofing requirements for residential wet areas.

External Above-Ground Waterproofing – AS 4654

Covers external membranes for balconies, roofs, and podiums.

Building Code Compliance – NCC

The National Construction Code governs performance requirements for waterproofing across Australia.

Additional standards may apply depending on:

• Concrete design
• Expansion joints
• Sealants
• Roofing systems
• Fire compliance
• Façade design

Balconies are among the highest-risk waterproofing areas because they combine:

• UV exposure
• Structural movement
• Thermal expansion
• Drainage challenges
• Multiple trade interfaces

Common balcony failure causes:

• Inadequate falls
• Blocked drainage
• Poor membrane detailing
• No movement joints
• Edge termination failures
• Tile bed saturation
• Membrane punctures
• Incorrect design

Many balcony leaks originate at:

• Door thresholds
• Balustrade penetrations
• Corners and upturns
• Drain outlets

Proper design and sequencing are critical.

Falls and drainage are absolutely critical.

Even the best membrane can fail prematurely if water ponds continuously.

Australian Standards typically require: 1.80 internally in showers and 1:100 in wet areas outside of the shower area balconies and roof tops should also be 1:100 minimum.

Poor drainage causes:

• Ponding water
• Efflorescence
• Tile debonding
• Accelerated membrane degradation
• Slip hazards

Drainage design should include:

• Correct outlet placement
• Overflow provisions
• Hob and threshold detailing
• Screed falls
• Drain flange integration

Where waterproofing systems are left exposed, they should be periodically inspected and maintained.

Recommended maintenance includes:

• Cleaning drains and outlets
• Checking sealants and joints
• Monitoring movement cracks
• Inspecting membrane exposures
• Resealing where required

High-exposure areas such as balconies and rooftops benefit from scheduled inspections every few years.

Lack of maintenance can void warranties and significantly reduce membrane lifespan.

Under the National Construction Code (NCC) and Australian Standards including AS 3740:2021 Waterproofing of domestic wet areas, a bond breaker is defined as a component used to accommodate movement and prevent stress transfer to the waterproofing membrane at joints, junctions, penetrations, and changes in substrate direction.

Bond breakers are required to:

• Isolate movement between adjoining building elements
• Prevent membrane rupture caused by stress concentration
• Allow the waterproofing membrane to bridge joints and transitions
• Maintain continuity of the waterproofing system

Missing bond breakers are a very common defect.

Buildings move due to:

• Thermal expansion
• Structural settlement
• Vibration
• Moisture changes

Without movement joints:

• Tiles crack
• Grout fails
• Membranes tear

Movement joints are essential in compliant waterproofing systems.

Yes, in some situations.

Tile-over systems can reduce demolition costs, but require:

• Strong tile adhesion
• Proper preparation
• Compatible primers
• Height and drainage assessment

Not all situations are suitable for overlay systems.