Laundry Waterproofing Requirements in Hobart: Australian Standards Explained

By Daniel Whitfield · September 6, 2026 · 11:14 am

We got called out to a place in Lenah Valley a while back, weatherboard cottage, laundry “renovated” about eight years earlier by the previous owner. New cabinets, new tap, looked the business. Problem was, when we pulled the vinyl up to fix a soft spot near the trough, there was no membrane under there at all. Just particleboard flooring gone grey and spongy, and a smell that told you mould had been having a party under there for years.

Nobody had done anything illegal exactly, but nobody had done it to AS 3740 either, which is the Australian Standard that actually governs laundry waterproofing requirements Hobart homes are supposed to meet. It's the difference between a laundry that lasts thirty years and one that's rotting from the inside within a decade, and most homeowners have no idea what they're meant to be checking for until something's already gone wrong.

Australian Standard AS 3740: What It Means for Your Laundry

AS 3740 is the national standard covering waterproofing of wet areas in Australian homes, and it applies just as much to your laundry as it does to your bathroom. The Australian Building Codes Board's National Construction Code provisions for wet areas reference AS 3740 directly, setting out what has to be protected against water and how it needs to be done, covering everything from membrane type and thickness through to how floor-to-wall junctions are sealed.

In Tasmania, that standard isn't just a suggestion. The Building Act 2016 brings AS 3740 into force through Consumer, Building and Occupational Services (CBOS), the state body responsible for building compliance, and any renovation touching your laundry's wet area needs to be brought up to current standard as part of the work, not left as-is because it's "just a laundry."

What that means practically: a licensed waterproofer, a compliant membrane system, and a certificate of compliance you can actually produce if you ever sell the place or make an insurance claim.

Wall Waterproofing: How High Should It Go?

This is the bit that catches people out most, because the answer isn't "the same height everywhere." Directly around the trough, behind the tapware, and anywhere water can realistically splash straight onto the wall, the membrane needs to run considerably higher up the wall than it does on a wall that's just in the general vicinity of a wet area. General laundry walls typically only need a modest upstand off the floor, while the splash zones around taps and the trough itself usually need to be waterproofed much higher, often close to a metre or more, depending on the layout.

The exact heights come down to how your particular laundry is laid out, where the water actually goes when the machine's filling or the trough's in use, and that's a judgement call AS 3740 leaves to whoever's doing the waterproofing to get right for your specific room. It's one of the main reasons DIY jobs and dodgy renovations under-waterproof the walls, because it looks like overkill until the first time water actually gets flicked that high and finds the one patch that wasn't covered.

How Long Does Proper Waterproofing Last?

A membrane installed correctly, to AS 3740, by someone who's licensed and knows what they're doing, should easily see out 20 to 25 years, often the working life of the room itself. What actually shortens that lifespan isn't the membrane wearing out on its own, it's things like structural movement cracking it, a leaking appliance sitting undetected for months, or someone drilling into a wall years later without knowing what's underneath.

So, will your laundry be waterproofed properly? If it's done by a licensed waterproofing company using a compliant membrane, flood-tested before anything's covered over, and finished with a proper compliance certificate, yes, it will, and you'll have the paperwork to prove it whenever you need it. That's the whole point of the standard, it takes the guesswork out of a part of the house you're never going to see again once it's finished.