Bathroom Waterproofing in NSW: What Sydney Homeowners Need to Know

If you only remember one thing about bathroom renovations, make it this: tiles are not waterproof. Grout is porous, tiles crack and silicone eventually breaks down. What actually keeps water inside your shower is the waterproofing membrane underneath.

Bad waterproofing is one of the most common and most expensive building defects in Sydney homes. The damage often isn't visible for months or even years, and by then it can affect walls, floors, framing and the apartment below. Here's what you need to know before you renovate.

Why waterproofing matters so much

Every time you shower, water runs across tiles and grout and some of it gets through. On a properly waterproofed floor, that water reaches the membrane and is directed to the floor waste. Without that protection, it soaks into the subfloor, the wall framing or the concrete slab.

The results can include:

• Mould and musty smells
• Rotting timber framing and subfloors
• Loose and drummy tiles
• Damage to adjoining rooms and ceilings below
• Expensive disputes in apartment buildings

The rules in NSW

Bathroom waterproofing in Australia follows the National Construction Code and the Australian Standard for waterproofing of domestic wet areas, AS 3740. These set out which parts of a bathroom, laundry or toilet must be waterproof or water resistant, and how membranes, falls and junctions should be detailed.

In NSW, waterproofing should be carried out by a tradesperson who holds the appropriate licence, and residential building work over $5,000 must be done by a licensed contractor under a written contract. You can check any licence through NSW Fair Trading.

What good waterproofing looks like

When we waterproof a bathroom, these are the steps that matter.

1. A properly prepared substrate

The surface needs to be clean, sound and suitable for the membrane. Floors are screeded where needed to create the correct fall to the floor waste, so water drains away instead of pooling.

2. Bond breakers at junctions

Walls and floors move slightly over time. At internal corners and wall to floor junctions, a bond breaker or flexible sealant lets the membrane stretch rather than crack.

3. Puddle flanges and penetrations

Floor wastes need the right fittings so the membrane connects properly to the drain. Taps, shower roses and other penetrations through the wall are sealed carefully.

4. The membrane itself

The membrane is applied at the right thickness, usually in more than one coat, across the whole shower area and to the required heights on walls and across floors.

5. Curing and inspection

Membranes need time to cure before tiling. On many jobs a flood test is done to check for leaks. It's not the most exciting week of a renovation, but it's the most important. Our bathroom renovation timeline shows where this fits.

6. Certification

At the end of the job, you should receive a waterproofing certificate. Keep it with your home records. It matters when you sell, and it matters if anything goes wrong.

Waterproofing in apartments

In apartment buildings, a leak doesn't just affect you. It can damage the unit below and common property. That's why most strata schemes in NSW require owners corporation approval for bathroom renovations that involve waterproofing, and may ask for details of the waterproofer, the products used and the certificate. Our guide to renovation approvals in NSW explains strata approvals in more detail.

Questions to ask your bathroom renovator

1. Who will do the waterproofing, and are they licensed?
2. Which standard will the work comply with?
3. Which membrane system will you use?
4. How will you handle falls, junctions and penetrations?
5. How long will the membrane cure before tiling?
6. Will you do a flood test?
7. Will I receive a waterproofing certificate?

If a builder can't answer these clearly, keep looking. You'll find more in our guide to choosing a renovator in Sydney.

Don't save money on waterproofing

When budgets are tight, it's natural to look for savings. Waterproofing is not the place to find them. It's a small part of the overall cost of a bathroom renovation, and redoing a failed bathroom costs far more than doing it right the first time. Our bathroom renovation cost guide shows where you can save instead.

Bathroom renovations done properly

Every bathroom renovation and laundry renovation we complete in Sydney is waterproofed by licensed trades and finished with a certificate. If you'd like advice on your bathroom, get in touch for a free consultation.