Poor waterproofing is one of the leading causes of costly home repairs in Australia. Whether you're renovating a bathroom, building a balcony, or adding a laundry, getting waterproofing right the first time is critical. At Velliss Building, we've seen the consequences of waterproofing done poorly — and it's almost always more expensive to fix than it would have been to do correctly from the start.
Here are the most common waterproofing mistakes homeowners and builders make, and how to avoid them.
1. Skipping the Waterproofing Membrane Entirely
It sounds obvious, but some renovation projects — particularly DIY jobs or budget builds — skip the waterproofing membrane altogether. Tiles alone are not waterproof. Grout lines allow water to seep through over time, and without a proper membrane underneath, moisture will eventually reach the substrate and cause damage.
The fix: Always apply a compliant waterproofing membrane to all wet areas before tiling. In NSW, this is a requirement under the National Construction Code.
2. Not Allowing the Membrane to Cure Properly
Rushing the job is one of the most common mistakes on site. Waterproofing membranes need adequate drying and curing time before tiles are laid on top. Tiling too early can compromise the membrane's integrity and lead to premature failure.
The fix: Follow the manufacturer's recommended cure time — typically 24 to 48 hours depending on the product and conditions. Don't let schedule pressure cut corners here.
3. Missing Critical Junctions and Corners
Floor-to-wall junctions and internal corners are the most vulnerable points in any wet area. These are the spots where movement occurs and where water is most likely to find a path through. Many waterproofing failures start at these junctions.
The fix: Use reinforcing tape or bandage at all junctions and corners before applying the membrane. This adds flexibility and prevents cracking at stress points.
4. Inadequate Coverage or Membrane Thickness
Applying the membrane too thinly — or missing sections entirely — leaves gaps in protection. Some applicators rush through the job and don't achieve the required film thickness, which means the membrane won't perform as rated.
The fix: Apply at least two coats of membrane, allowing each coat to dry before the next. Check the product data sheet for the required dry film thickness and verify coverage.
5. Using the Wrong Product for the Application
Not all waterproofing products are suitable for all applications. A product rated for internal showers may not be appropriate for an external balcony exposed to UV and temperature changes. Using the wrong product is a common and costly mistake.
The fix: Always match the product to the application. External areas, wet rooms, and below-ground applications each have specific requirements. When in doubt, consult a licensed waterproofer.
6. Not Getting It Inspected
In NSW, waterproofing in wet areas is a mandatory hold point — it must be inspected and approved before it's covered up. Skipping this step not only puts your home at risk but can also create issues when you come to sell.
The fix: Ensure your builder or waterproofer arranges the required inspection at the right stage of the build. At Velliss Building, we manage this process as part of every project.
Final Thoughts
Waterproofing is one of those things you don't think about until it fails — and by then, the damage is already done. Getting it right the first time protects your home, your health, and your investment.
At Velliss Building, we work with licensed waterproofers on every project to ensure your wet areas are sealed properly and built to last. If you're planning a renovation or have concerns about existing waterproofing, reach out to us today.
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