How to Apply Bond Breaker Tape in a Wet Area Correctly

Bond breaker tape is a critical — and often overlooked — part of any wet area waterproofing system. Applied correctly at internal corners and junctions, it allows the waterproofing membrane to flex and move without cracking, keeping your shower or bathroom watertight for years to come.

What Is Bond Breaker Tape and Why Does It Matter?

Bond breaker tape (sometimes called cove tape or foam backing tape) is a compressible foam or polyethylene strip applied into internal corners and junctions before the waterproofing membrane goes on. Its job is to prevent the membrane from bonding rigidly to both surfaces at once — which would cause it to tear when the building moves or materials expand and contract.

Without bond breaker tape, even a high-quality membrane can crack at corners over time, leading to water ingress, substrate damage, and costly repairs. This is why its use is standard practice under BRANZ guidelines and is required to meet the NZ Building Code clause E3 (Internal Moisture).

What You'll Need

• Bond breaker tape (foam backing rod tape, typically 6–10 mm wide)
• Waterproofing membrane compatible with your system (liquid-applied or sheet)
• Primer (if required by your membrane manufacturer)
• Clean cloth or brush
• Scissors or a sharp knife
• Waterproofing brush or roller

Always check that your bond breaker tape is compatible with your chosen membrane system. Brands like Ardex, Mapei, and Sika all offer wet area waterproofing systems with recommended tapes — follow the manufacturer's specifications closely.

Step-by-Step: Applying Bond Breaker Tape Correctly

1. Prepare the Surface

Before anything goes down, the substrate must be clean, dry, and structurally sound. Remove any dust, grease, or loose material. If you're working over GIB Aqualine or fibre cement sheet, ensure all screws are set and joints are stopped and sanded flush. Any high spots or voids at corners should be made good first.

2. Prime if Required

Many membrane systems require a primer coat before the tape is applied, particularly on porous substrates. Check your membrane's technical data sheet — skipping this step can affect adhesion and void your product warranty.

3. Apply the Bond Breaker Tape to All Internal Corners

This is the key step. Apply bond breaker tape to every internal corner and junction in the wet area, including:

• Floor-to-wall junctions (all four corners of a shower floor)
• Wall-to-wall internal corners
• The junction between the shower floor and any hob or step
• Around any penetrations (pipes, drains) if specified by your system

Press the tape firmly into the corner so it sits snugly, but do not stretch it — stretching reduces its ability to compress and flex. Cut neatly at ends and overlap joins by at least 50 mm. The tape should be centred in the corner, not pushed hard to one side.

4. Embed the Tape in the First Coat of Membrane

Apply a coat of liquid membrane over the tape, pressing it in firmly with your brush so there are no air bubbles or lifted edges. The membrane should fully encapsulate the tape on both sides. This is what locks the tape in place while still allowing it to flex.

5. Apply Full Membrane System Over the Top

Once the first coat has cured (check your product's recoat time — this varies by brand and temperature), apply subsequent coats of membrane over the entire wet area, including over the taped corners. Most systems require a minimum of two coats to achieve the required dry film thickness. Always check the manufacturer's specifications for your specific product.

6. Check Your Work Before Tiling

Before tiling, visually inspect all corners. The membrane should be continuous, with no pinholes, thin spots, or lifted tape edges. Some installers do a simple flood test (blocking the drain and filling with water for 24 hours) to confirm integrity — this is good practice on shower floors.

Common Mistakes to Avoid

NZ Building Code and Consent Considerations

Wet area waterproofing in NZ must comply with Building Code clause E3 (Internal Moisture). In most cases, replacing or installing waterproofing in a shower or bathroom is exempt from building consent under Schedule 1 of the Building Act — but you should always confirm this with your local council before starting work, as exemptions have conditions. See MBIE Building Performance for guidance on what work requires consent.

If your wet area work involves moving or installing plumbing, that work must be carried out by a licensed tradesperson registered with the Plumbers Gasfitters & Drainlayers Board.

When to Call a Professional

While a competent DIYer can apply bond breaker tape and membrane in a straightforward shower renovation, there are times when it pays to bring in a qualified waterproofer:

• Large or complex wet areas (steam rooms, tiled baths, large format tiles)
• If the existing substrate is damaged, soft, or showing signs of previous water damage
• If you're unsure which membrane system suits your substrate
• When the work is part of a larger renovation requiring building consent
• If you want a manufacturer's warranty to be valid (some require licensed applicator installation)

A qualified waterproofer will know the right products for NZ conditions and can ensure the work meets E3 requirements. You can find experienced local waterproofing tradespeople on tradedirectory.co.nz.

Sources & Further Reading

• BRANZ – Wet Area Waterproofing Guidance
• MBIE Building Performance – Building Code Clause E3
• Ardex NZ – Waterproofing Systems
• Mapei NZ – Waterproofing Products
• Sika NZ – Waterproofing Solutions
• GIB – Wet Area Substrates