Whether a laundry needs waterproofing depends on the floor waste configuration and state regulations. The rules have changed over the years, causing confusion among homeowners and even some builders. We explain the current Australian requirements and connect you with licensed waterproofers who ensure compliance.
The Short Answer on Laundry Waterproofing
Under AS 3740-2021, which is the Australian Standard for waterproofing of domestic wet areas, a laundry that has a floor waste requires waterproofing. The waterproof membrane must extend across the entire floor and up walls to a minimum of 150 millimetres above the finished floor level. If there is no floor waste installed in the laundry, waterproofing is not mandated by the standard, though some state variations, local council requirements, and building certifiers may still require it. This distinction between laundries with and without floor wastes is the source of much confusion among homeowners, builders, and even some tradespeople. Understanding the specific requirements helps you make informed decisions about your laundry.
Queensland Requirements Under the QBCC
In Queensland, the QBCC enforces compliance with AS 3740 as part of the building approval process. This means laundries with floor wastes must be fully waterproofed by a licensed waterproofer before tiling or floor finishing can proceed. The QBCC requires that waterproofing is carried out by a contractor holding the appropriate waterproofing licence class, and that a waterproofing certificate is issued confirming the work complies with AS 3740. Building certifiers will inspect the waterproofing installation before allowing tiling to proceed. Even where a floor waste is not present and waterproofing is not strictly mandated, the QBCC strongly recommends waterproofing laundry floors as a protective measure against water damage from appliance failures and overflows.
Why the Floor Waste Makes the Difference
The presence of a floor waste in a laundry changes the waterproofing requirement because a floor waste implies that the room is designed to receive and drain water on the floor surface. If water is expected on the floor regularly enough to justify a drain, then the floor and lower walls must be waterproofed to prevent that water from penetrating the building structure. Without a floor waste, the assumption is that water should not accumulate on the floor during normal use. However, this assumption does not account for the very real risk of appliance failures, burst hoses, and accidental flooding that can release large volumes of water onto a laundry floor regardless of whether a floor waste is present.
The Case for Waterproofing Every Laundry
Insurance industry data consistently shows that washing machine failures are among the most common sources of water damage claims in Australian homes. A burst inlet hose can release hundreds of litres of water in minutes, while a failed drain pump or blocked outlet can cause overflow during every wash cycle. Front-loading washing machines, which are increasingly popular, trap water behind the door seal that can leak if the seal deteriorates. Even a small, slow leak from a washing machine connection can cause significant damage over time if the laundry floor is not waterproofed. The cost of waterproofing a laundry floor during construction or renovation is modest compared to the potential cost of repairing water damage to floor structures, adjacent rooms, and the rooms below in multi-level homes.
Laundry Waterproofing Requirements Under AS 3740
When waterproofing is required in a laundry, AS 3740-2021 specifies the minimum performance requirements. The waterproof membrane must cover the entire floor area and extend a minimum of 150 millimetres up all walls. Behind and beneath the washing machine connection point, the membrane should extend higher to protect against splashes and minor leaks at the connection. The membrane must be continuous, with all joints and junctions properly sealed. Floor wastes must be integrated into the membrane with proprietary puddle flanges that create a watertight seal between the membrane and the drain fitting. The membrane must pass a flood test before tiling or floor finishes are applied, verifying its integrity under standing water conditions.
Waterproofing Laundries in Multi-Level Buildings
Laundry waterproofing becomes particularly important in multi-level buildings, whether apartment complexes or multi-storey houses, because water escaping from an upper-level laundry can damage the structure below and affect other units or rooms. In apartment buildings, a laundry leak can travel through the floor structure and appear in the ceiling of the unit below, causing damage to finishes, furniture, and personal property. The building owner or occupier of the unit where the leak originates may be liable for this damage. For this reason, many building certifiers and strata managers in Brisbane require laundry waterproofing regardless of whether a floor waste is present, recognising the significant risk that appliance failures pose in multi-level situations.
Laundry Waterproofing During Renovation
If you are renovating your laundry, it is the ideal time to add or replace waterproofing whether or not it is strictly required by the standard. During a renovation, the floor finishes are typically removed, exposing the substrate for membrane application. Adding waterproofing at this stage costs relatively little compared to the overall renovation budget and provides lasting protection against future water damage. If a floor waste is being added as part of the renovation, waterproofing becomes mandatory under AS 3740. Your QBCC-licensed waterproofer can advise on the best membrane system for your laundry, taking into account the substrate type, the planned floor finish, and the positions of washing machine connections, tubs, and any floor wastes.
Common Laundry Water Damage Scenarios
Understanding how water damage occurs in laundries helps illustrate why waterproofing is a smart investment. Burst washing machine inlet hoses are the most dramatic scenario, releasing mains-pressure water onto the floor for as long as the supply remains connected. Blocked or kinked drain hoses cause the machine to overflow during the pump-out cycle. Failed door seals on front-loading machines allow water to seep out during wash cycles. Leaking taps at the washing machine connection drip steadily, causing concealed damage over months. Overflowing laundry tubs send water across the floor when drains are slow. In each of these scenarios, a waterproofed laundry floor contains the water and directs it to the floor waste, preventing structural damage.
Laundry Waterproofing Materials and Methods
Laundry waterproofing uses the same membrane systems and application methods as bathroom waterproofing. Liquid-applied membranes, either acrylic or polyurethane based, are the most common choice for laundry floors. These are applied by roller or brush in multiple coats, building up a seamless waterproof layer across the floor and up the walls. Sheet membranes can also be used, particularly for larger laundry areas or where the substrate is difficult. The membrane is applied over a prepared substrate, with reinforcement tape at all internal corners, wall-to-floor junctions, and around penetrations. Puddle flanges are installed at floor wastes before the membrane is applied, ensuring a watertight connection between the membrane and the drain.
Flood Testing Your Laundry Waterproofing
After the waterproof membrane is installed and has cured, a flood test verifies its integrity before tiling or floor finishes are applied. The floor waste is temporarily plugged, and the floor is flooded with water to a depth that covers the entire membrane surface, typically to the level of the wall upstand. The water is left standing for a minimum period, usually 24 hours, while the adjacent areas and the underside of the floor are inspected for any signs of leakage. If the flood test reveals any leaks, the membrane must be repaired and retested before tiling can proceed. Building certifiers in Queensland typically require documented flood test results as part of the waterproofing compliance process.
Insurance Implications of Laundry Waterproofing
Home insurance policies in Australia generally cover sudden and accidental water damage, such as damage from a burst washing machine hose. However, insurers may reduce or deny claims where the damage resulted from a lack of reasonable maintenance or where required waterproofing was not installed. Having a properly waterproofed laundry with documented compliance certificates demonstrates due diligence in protecting your property. In body corporate situations, individual lot owners may be held liable for water damage to common property or other lots if their laundry waterproofing is deficient. The relatively modest cost of laundry waterproofing provides significant financial protection against these potential liability scenarios.
Get Your Laundry Waterproofed in Brisbane
Whether your laundry requires waterproofing under the current standards or you want the peace of mind that comes with protecting your home against appliance failures, professional laundry waterproofing is a smart investment. We connect you with QBCC-licensed waterproofers who ensure your laundry waterproofing meets all applicable Australian Standards and Queensland requirements. Whether you are building a new home, renovating an existing laundry, or adding waterproofing to a laundry that currently lacks protection, our network of experienced professionals can provide the expert installation you need. Request your free quotes and protect your home today.
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