Can I do waterproofing myself if I’m a licensed builder? (Bathroom | Building & Approvals)

Waterproofing is one of the most critical aspects of any bathroom renovation in Sydney. It protects your home from water damage, mould, and structural issues, ensuring your bathroom remains safe, functional, and compliant with Australian Standards. Naturally, licensed builders often ask: “Can I do waterproofing myself if I’m a licensed builder?” The short answer is yes—but there are important regulatory, technical, and quality considerations to understand.

Understanding Waterproofing Requirements in Sydney

In Sydney, bathroom waterproofing is strictly regulated under the Building Code of Australia (BCA) and Australian Standards AS 3740: Waterproofing of Wet Areas. These standards define the correct materials, installation methods, and inspection requirements for wet areas, including:

• Shower recesses

• Bathroom floors

• Ensuite wet areas

• Laundry floors (if combined with a bathroom)

• Toilet areas in multi-purpose renovations

Even as a licensed builder, you must follow these standards precisely to ensure the work is compliant, safe, and acceptable to councils, private certifiers, and future buyers.

When a Licensed Builder Can Do Waterproofing

In Sydney, a licensed builder is generally permitted to undertake waterproofing work in a bathroom if:

1. You hold the appropriate license
   Licensed builders in NSW may perform waterproofing as part of a bathroom renovation under their license, provided they comply with the regulations. However, if the project involves complex waterproofing or specialized products (like liquid-applied membranes), some councils or clients may still require a licensed waterproofing contractor.

2. Compliance with Australian Standards
   All work must meet AS 3740: 2021 Waterproofing of Wet Areas Within Residential Buildings. This includes proper surface preparation, membrane application, curing time, and testing.

3. Correct Documentation and Certification
   Sydney councils often require a Certificate of Compliance for waterproofing as part of the inspection and final approval process. As a licensed builder performing the work yourself, you must provide certification that meets NSW legal and council requirements.

4. Appropriate Materials and Techniques
   Using approved membranes, primers, tapes, and sealants is essential. Builders must ensure:

   • Substrate surfaces are properly prepared and primed

   • Membranes are applied evenly without gaps

   • Corners, junctions, and penetrations (drains, pipes) are reinforced

   • Curing times are respected before tiling or installation of fixtures

Regulatory and Compliance Considerations

Even if you are a licensed builder in Sydney, you cannot overlook regulations:

1. Council and Private Certifier Requirements
   For renovations requiring a DA or CDC, councils may request waterproofing certification. Some councils allow licensed builders to issue the certification themselves, while others require a specialist waterproofing contractor. Pre-lodgement advice from your council can clarify requirements.

2. Insurance and Warranty Implications
   Performing waterproofing yourself may affect insurance claims if leaks occur. Some homeowner insurance policies or builder warranty schemes require waterproofing to be done by a specialist with proper certification.

3. Scope of Work Limitations
   While you may perform standard wet area waterproofing, complex areas such as:

   • Large or curbless showers

   • Wet rooms

   • External balconies integrated with bathrooms
     may require a dedicated waterproofing contractor to meet compliance.

Technical Steps for Builders Performing Waterproofing

As a licensed builder, you must follow a structured process for bathroom waterproofing to ensure compliance and longevity:

1. Surface Preparation

   • Clean and level the substrate

   • Repair cracks, holes, or damaged surfaces

   • Apply primer if required by the membrane manufacturer

2. Application of Membrane

   • Apply waterproofing membrane (liquid-applied or sheet membrane) evenly

   • Reinforce corners, wall-floor junctions, and penetrations with mesh or fabric

   • Ensure membrane thickness meets manufacturer and AS 3740 specifications

3. Curing and Testing

   • Allow the membrane to cure fully before tiling or installing fixtures

   • Conduct a flood test if required to check for leaks

4. Documentation and Certification

   • Record materials, batch numbers, application dates, and curing times

   • Provide certification or compliance statement for council or private certifier inspection

Benefits of Licensed Builders Doing Waterproofing

1. Cost Savings
   Performing waterproofing yourself reduces the need to hire a specialist contractor, which can save on labour costs.

2. Better Project Control
   As the builder managing the entire bathroom renovation, you can coordinate waterproofing, tiling, and plumbing more efficiently, reducing delays.

3. Enhanced Skills and Reputation
   Demonstrating mastery of waterproofing can strengthen your reputation as a competent, versatile builder in Sydney’s competitive renovation market.

Risks and Challenges

• Strict Compliance Requirements: Even minor errors in waterproofing can lead to water damage, mould, and council non-compliance.

• Insurance and Warranty Limitations: Some policies may not cover DIY waterproofing even if performed by a licensed builder.

• Inspection Requirements: Council or private certifier inspections may reject substandard waterproofing, requiring costly rework.

Tips for Sydney Builders Performing Waterproofing

1. Stay Updated on AS 3740 and BCA Regulations
   Standards are periodically updated. Ensure your methods, membranes, and processes comply with the latest versions.

2. Use Certified Materials
   Only use waterproofing products approved by the manufacturer and compliant with Australian Standards.

3. Document Everything
   Maintain detailed records of preparation, membrane application, curing, and testing. Proper documentation supports council compliance and future insurance claims.

4. Consider Third-Party Certification for Complex Jobs
   For larger or complex wet areas, engaging a specialist to provide certification can mitigate risks and reassure clients or councils.

5. Coordinate with Other Trades
   Plumbing, electrical, and tiling work must align with waterproofing schedules to prevent delays and ensure a fully compliant wet area.

Key Takeaways for Sydney Builders

• Licensed builders in Sydney can perform bathroom waterproofing themselves, provided they meet AS 3740, council regulations, and NSW building codes.

• Proper certification, documentation, and inspection compliance are essential to avoid legal, insurance, or structural issues.

• Complex wet areas or high-risk installations may still require a specialist waterproofing contractor.

• Performing waterproofing in-house offers cost savings, project control, and skill development, but comes with strict responsibility for quality and compliance.

• Staying updated on the latest waterproofing standards, using approved materials, and coordinating inspections ensures that your bathroom renovation is safe, compliant, and long-lasting.

Waterproofing is the foundation of a successful bathroom renovation. For Sydney builders, performing this work yourself can be efficient and cost-effective, but it must be done carefully, correctly, and in accordance with all regulations. Properly executed waterproofing protects the home, ensures compliance with councils and certifiers, and delivers a durable, functional bathroom that adds value and comfort for homeowners.

For professional guidance or full bathroom renovation services, including certified waterproofing, visit www.mb9.com.au to discover how MB9 Australia Pty Ltd supports Sydney homeowners and licensed builders in achieving compliant, high-quality bathroom renovations.