Tiles are perhaps the best floor for wet areas. No other flooring material is as waterproof as tiling, except perhaps cement. And cement is hardly an attractive material for indoors. For this reason, almost every home bathroom, as well as many kitchens and laundries, has tiled floors, and often tiled walls. But of course, it is also important to waterproof the flooring beneath the tiles. These tiled areas are frequently exposed to moisture. And anything less than a perfectly tiled surface will suffer some leaks. It is all too easy for water to easily seep through grout lines, tile joints, and small gaps. This hidden moisture causes structural damage, mould growth, and expensive long-term problems. It is better to waterproof the floor at the start than suffer serious and costly problems later on.
Sydney homeowners must be aware that there are fairly strict government regulations about waterproofing in bathrooms and other wet areas of the house. These regulations need to be applied before any tiling is done in the home.
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Why Waterproofing Is Essential
Prevents structural damage
Water that penetrates behind tiles can damage timber floors, plasterboard, concrete slabs, and metal reinforcements. Over time, this leads to rot, swelling, and deterioration of the building structure.
Stops mould and mildew
Moisture trapped beneath tiles provides ideal conditions for mould and mildew. This can be a serious health issue, especially as some moulds release toxins in the air. A waterproof membrane will prevent water leaking past the subfloor where the tiles are, greatly reducing any risk of mould growth.
Protects tile adhesion and grout integrity
Excess moisture soon weakens the adhesive that holds tiles in place. This leads to loose tiles, which subsequently let more water through. Proper waterproofing helps maintain the bond between tiles and substrate, improving durability.
Avoid Costly Repairs
Water damage is often insidious, occurring under the floorboards or behind walls. It may not be noticed until it is severe. And severe damage can be very expensive to repair. Repairs may involve re-tiling, replacing damaged flooring, or even rebuilding sections of walls or bathrooms. Waterproofing is a cost-effective preventive measure.
Improves long-term durability
By protecting the substructure beneath the floor from daily water exposure, waterproofing helps tiled areas last longer and function better. This means fewer interventions will be required over time.
The Risks of Skipping Waterproofing
It is better to have waterproofing under the tiled floor. If we neglect this waterproofing we risk safety and hygiene problems.
• Water leaks through floors and walls
• Cracking and weakening of timber or concrete
• Persistent dampness, which encourages mould growth
• Tile failure – the tiles come loose
• Structural weakening, which can be severe in multi-storey buildings
In Australia, waterproofing is also regulated. According to Australian Standard AS 3740, all domestic wet areas require waterproofing. In some states, such as Queensland, waterproofing valued over $3,300 must be completed by a licensed professional.
Areas Where Waterproofing Is Critical
Bathrooms
Showers, floors, and walls are regularly exposed to large volumes of water. Without waterproofing, moisture easily penetrates behind tiles and causes long-term damage.
Kitchens
Splashes, steam, and sink overflows can introduce moisture. Waterproofing protects cabinetry bases, walls, and subfloors.
Laundry rooms
Leaks from washing machines and pipes can cause damage, especially if the room is not adequately sealed.
Balconies
Balconies must withstand rain, humidity, and temperature changes. Waterproofing prevents water from travelling into the structure and causing cracks or failure.
Swimming pools
Pool areas require robust waterproofing to prevent water migration that could damage the pool shell or surrounding surfaces.
Common Waterproofing Methods
Liquid membrane waterproofing
A popular method for bathrooms and showers. It forms a seamless, flexible barrier suitable for corners and complex surfaces.
Sheet membrane waterproofing
Used for larger areas such as balconies and rooftops. Sheet membranes are durable, reliable, and suitable for outdoor conditions.
Crack injection and joint sealing
Used in areas where movement is expected. This ensures gaps and junctions remain sealed even when surfaces shift.
How Proper Waterproofing Supports Tiling
A correct waterproofing system improves adhesion, strengthens surface stability, and reduces the likelihood of future tile-related issues. In many installations, moisture-resistant cement backer boards are also installed to create a stable base before applying waterproof membranes.
Professional vs DIY Waterproofing
DIY waterproofing is possible for small, simple areas, but wet rooms, bathrooms, and balconies are high-risk spaces. Poor application is one of the leading causes of waterproofing failure. Professional waterproofing ensure correct preparation, membrane thickness, curing time, and compliance with Australian standards.
Why Waterproofing Matters Beneath the Surface
Homeowners may assume tiles are waterproof. But seemingly minor damage, initially going unnoticed, may allow water to pass through the tile surface to the floor below. Over time, this leads to loose tiles, mould, and hidden structural decay that can be very serious. Waterproofing creates a durable foundation that keeps moisture out. This significantly extends the life of the tiled floor. It also ensures compliance with building requirements and maximises the durability of tiled surfaces. Whether you are renovating a bathroom, updating a laundry, or tiling a balcony, proper waterproofing provides long-term protection and saves significant repair costs.
