The plumbing side of a bathroom renovation on the Gold Coast (2026 guide)

A bathroom reno is really two jobs stacked on top of each other. There's the bit you chose, the tiles, the vanity, the tapware, the screen. And there's the bit underneath it that nobody picks on Pinterest, the drainage, the water lines, the falls and the waterproof membrane. The second bit is the one that comes back to bite people, because once the tiles are on you can't see any of it, and fixing it means tearing the room apart again.

This is the plumbing and waterproofing of a reno explained honestly. We've left the detailed dollar figures to our bathroom reno cost guide, because every job is different and the only number that matters is the one in your written quote. What this guide covers is the sequence, why the order can't be messed with, and where things go wrong.

The plumbing happens in stages, and the order is everything

A bathroom reno isn't one trade turning up and doing the lot. It's a chain of trades who each have to finish before the next can start. The plumber is on site at the beginning, in the middle and at the end, and in between the waterproofer and tiler do their bit. Get the order wrong and you're ripping out finished work.

Here's the sequence the way it runs on a typical Gold Coast bathroom.

Notice the plumber bookends the job. We rough in at the start, then disappear while the waterproofer and tiler work, then come back to fit off at the end. Coordinating those gaps is where a lot of renos run over time.

Strip-out, where the surprises live

Strip-out is the first day or two. The old vanity, toilet, shower and tiles come out, the wall lining comes off, and the existing water and waste get capped so the rest of the house keeps running. It looks like demolition, but for a plumber it's the first proper diagnosis of what we're actually dealing with.

This is where older Gold Coast homes throw up surprises. Behind the tiles we regularly find:

• Failed old waterproofing – in homes from before about the mid-90s there's often no proper membrane at all, just tiles stuck to a bed that's been quietly letting water through for years.
• Rotten or water-damaged framing – timber studs and floor that have been wet for a long time and have started to go. This is common where an old shower leaked slowly without anyone noticing.
• Corroded copper – in older coastal homes the copper water lines can be pitted and thin, especially anywhere salt air has worked on them.
• Asbestos lining – bathrooms in pre-1990 homes can have asbestos cement sheet behind the tiles, which has to be removed and disposed of properly by a licensed remover.
• Drainage that's nothing like the plan – old houses get added to and patched over decades, and the waste often doesn't run where anyone expects.

None of this is a reason to panic, but it is a reason why an honest plumber won't give you a final fixed price for a strip-and-rebuild without allowing for the unknown. We'd rather flag a contingency up front than spring a surprise bill on you on day two. Our bathroom reno mistakes guide goes deeper on the hidden-damage traps.

Rough-in and relocating fixtures, what's easy and what isn't

Rough-in is the heart of the plumbing job. It's where we run all the new water lines and drainage, set out every fixture, and get everything ready before the walls and floor close up. Once the cement sheet is on and the membrane is down, what we've done here is locked in.

The big question most people have is "can we move the shower / toilet / vanity?" The honest answer is: it depends entirely on which fixture, and on the drainage, not the water.

Water lines are easy to move. Drains aren't.

Hot and cold water lines are under pressure, so they can run uphill, around corners, wherever we need them. Moving where a tap or shower comes out of the wall is usually straightforward. Drainage is the opposite. Waste runs on gravity, which means it has to fall continuously toward the sewer at a set grade. You can't make a drain run uphill, and you can't bend it sharply without risking blockages.

So the rule of thumb on relocating:

• Basin / vanity – usually the easiest to move. Small waste, flexible position, often just a matter of running a new branch.
• Shower – moveable, but the floor waste has to be repositioned and the floor re-screeded so the fall still runs to the new drain. More work, more cost, but doable in most rooms.
• Toilet – the hardest. The toilet waste is the biggest pipe in the room and needs the most fall. Shifting it more than a short distance can mean cutting into the slab or floor to re-route the drain, which is a serious job. On a concrete slab that's a much bigger deal than on a timber floor.

This is why "we'll just open the space up" sounds simple and isn't. If your new layout keeps the toilet, shower and basin roughly where they are, you save a lot of money and avoid the riskiest work. If the layout has to change, get it locked on paper before rough-in, because once the drains are set, they're set.

While we're in there at rough-in, we also pressure test every joint before the walls close. Finding a leak now is a five-minute fix. Finding it after the tiles are on is a demolition job.

Waterproofing, the stage that makes or breaks the whole reno

If there's one part of a bathroom reno worth being fussy about, it's the waterproofing. It's a thin membrane you'll never see again once the tiles go on, and it's the single thing standing between your shower water and the timber, plaster and structure of your house. Get it right and you forget it exists. Get it wrong and it's a five-figure tear-out.

In Queensland, waterproofing a wet area is regulated work that must be done to Australian Standard AS 3740 (waterproofing of domestic wet areas). It's not a job for whoever's cheapest. The membrane has to be applied to the right areas, to the right height up the walls, lapped correctly, and sealed around every single penetration the plumber made, every waste, every set of tap holes, every drain.

Where it sits in the order is the whole point. Waterproofing goes on after the plumber has finished rough-in and the floor has been screeded, and before the tiler lays a single tile. That sequence is non-negotiable. The membrane has to seal around the drain and the pipe penetrations, then the tiles go over the top of the cured membrane. Out of order and you've either got penetrations that aren't sealed or a membrane you have to drill straight back through.

The other thing people rush is the cure. The membrane needs time to dry and cure properly before tiling, and on a humid Gold Coast week that can take longer than the tin says. You cannot hurry it. Tiling over a membrane that hasn't cured is one of the classic causes of failure.

We've kept the full deep-dive in our dedicated bathroom waterproofing guide, which is worth reading before you sign off on any reno quote. The short version: it's the cheapest insurance in the whole job and the worst place to save money.

Falls and drainage, why your shower floor isn't flat

A shower floor looks flat. It isn't, and it shouldn't be. Every wet area floor is built with a deliberate slope, the fall, so that water runs to the drain instead of pooling or escaping across the room. That fall is created in the screed bed before the tiles go on, and the tiler follows it.

This matters more than people realise. A shower with a dead-flat or badly-set floor holds water after every use, and standing water means mould, smell, grout breakdown and eventually waterproofing stress. A shower with proper fall is dry within minutes. It's the difference between a bathroom that ages well and one that's grim in three years.

Floor waste vs linear drain

There are two common ways to drain a shower, and the choice affects the falls.

• Centre (or corner) floor waste – the traditional square or round grate in the floor. The floor has to fall toward that point from every direction, which on larger tiles means more cuts and a slightly dished look. Cheapest and simplest, works fine.
• Linear (channel) drain – a long, narrow strip drain, usually set against one wall or across the shower entry. Because all the water runs one direction, the floor only needs to fall one way. That lets you use big-format tiles laid in a single plane, which looks cleaner and is popular in modern renos. It costs more to buy and to install, and the set-out has to be spot on.

Neither is "better", they're a trade-off between budget and look. What matters either way is that the fall is set correctly and the waste sits at the low point. A beautiful linear drain set into a floor with the wrong fall still leaves water sitting in the shower.

Choosing and supplying the fixtures

The fixtures, the tapware, mixers, shower, toilet and so on, get connected at fit-off, but the decisions have to be made much earlier. The reason is set-out. Wall-mounted mixers and bath spouts have specific centres (the gap between the hot and cold supply points) that vary by brand and model. If we rough in for one tap and you turn up at fit-off with a different one, the holes don't line up, and fixing that means cutting back into finished tile.

So the rule is simple: choose your tapware before rough-in, not after. Give your plumber the actual brand and model so we set out to the right centres and heights the first time.

On the Gold Coast the coast itself drives a lot of fixture choice. Salt air is hard on cheap finishes, and budget chrome-plated brass can pit and dull within a few years near the beach when the same tap would last decades inland. For coastal bathrooms we steer people toward quality brass with a PVD finish or 316 stainless on anything exposed. We've written the whole story on what lasts and what doesn't in our guide to choosing tapware, and there's a quick answer on the best tapware for a Gold Coast bathroom if you just want the short version.

One more thing on supplying your own fixtures. You can save money buying tapware yourself, but check two things: that it's WaterMark certified (the certification that confirms it's legal to install in Australian plumbing, a lot of cheap online tapware isn't), and that the brand's warranty doesn't require licensed installation through authorised channels. If it's not WaterMarked, we can't legally fit it.

Who does what, and why coordination matters

A bathroom reno typically involves a plumber, a waterproofer, a tiler, and often a builder or carpenter, plus an electrician for lights, the exhaust fan and the heated towel rail. Each has a defined patch:

• Plumber – strip-out, all drainage and water rough-in, fixture set-out, and the final fit-off. Plus the compliance paperwork.
• Waterproofer – the membrane to AS 3740. In Queensland this is its own licensed trade, separate from general plumbing.
• Tiler – screed and falls (on many jobs), then floor and wall tiling over the cured membrane.
• Builder / carpenter – framing changes, niches, hob construction, and lining the walls.
• Electrician – lights, exhaust fan, power, heated towel rail. Their work runs alongside the plumbing rough-in.

The reason coordination matters so much is that these trades hand off to each other in a fixed order, and a delay anywhere stalls the whole chain. The plumber can't fit off until the tiler's done; the tiler can't start until the membrane's cured; the membrane can't go on until the plumber's roughed in and the floor's screeded. One trade running a day late pushes everyone.

Most homeowners want one point of contact who manages that chain rather than juggling five trades themselves. That's the project-management role, and it's worth having whether your plumber runs it or a builder does. The renos that go sideways are almost always the ones where every trade was booked in isolation with nobody owning the sequence.

What goes wrong, and how it shows up later

The failures we get called back to fix nearly always trace to one of a handful of causes:

• Hidden damage missed at strip-out – tiling and waterproofing straight over rotten framing or a leaking old drain, so the new bathroom inherits the old problem.
• Bad falls – a shower floor that holds water, leading to mould, smell and grout failure within a couple of years.
• Failed waterproofing – the big one. A membrane that was rushed, skimped, applied too low up the walls, or not sealed around a penetration. Water gets behind the tiles and into the structure, and you don't find out until there's a damp wall in the next room or a stain on the ceiling below.
• Leaks after fit-off – a connection that wasn't done properly, or a fixture that was over-tightened. Usually caught at the final leak check, occasionally not.

The nasty thing about all of these is the time lag. A waterproofing failure can leak quietly for months before it surfaces, and by then the damage is done behind finished tiles. That's why the pressure test before the walls close, the proper membrane, and the falls being set right are non-negotiables, not extras. If you want to understand the specific ways leaks turn up after a reno, we've covered it in what causes bathroom leaks after a renovation.

How long the plumbing actually takes

People are surprised how little of a reno is plumbing, and how much is waiting. The plumbing itself, rough-in plus fit-off, is usually only a few days of actual work spread across the job. Rough-in is a day or two near the start. Fit-off is a day or so near the end.

The reason a bathroom is out of action for two to three weeks isn't that the trades are slow, it's the dependencies. The membrane has to cure. Tiles have to be laid and the adhesive and grout have to set. Some days nothing happens on site because something is drying. You're without the bathroom the whole time even though no single trade is there for the whole time.

The honest planning advice: if you've got a second bathroom, reno the one you use least first. If you've only got one, line up the trades tightly before you start so there are no dead days waiting on a trade who's gone to another job.

Getting it certified

Plumbing and drainage work in Queensland is licensed work, and a bathroom reno produces compliance obligations that protect you. The relevant points:

• The plumbing must be done by a licensed plumber – not a handyman, not the cheapest bloke off a marketplace. In QLD, regulated plumbing and drainage work is licence-only.
• The waterproofing must be done by a licensed waterproofer to AS 3740 – it's a separately licensed trade here, and the membrane should be documented (photos during install, and a certificate) so there's proof it was done.
• Notifiable work is certified by the licensed plumber – depending on the scope, the plumber lodges the compliance paperwork for the regulated drainage and plumbing work. Keep that paperwork; you'll want it when you sell.

The reason this matters beyond ticking a box: if your waterproofing fails and there's no documentation that it was ever done by a licensed trade, you've got no recourse and a potential insurance headache. The certification and the photos are your proof the unseen work was done right.

The bottom line

The plumbing and waterproofing of a bathroom reno is the part you can't see, can't easily fix, and absolutely have to get right. The fixtures and tiles are the fun decisions. The falls, the membrane, the drainage and the sequence are the ones that decide whether the room is still sound in 20 years. Choose the layout carefully, lock your fixtures before rough-in, never skimp on waterproofing, and use trades who own the sequence rather than working in isolation.

If you're planning a bathroom reno on the Gold Coast and want the plumbing side done properly, that's our lead service. Have a look at our bathroom renovations page, then ring us on 0472 657 042 or send the details through the contact page. We'll come and see the bathroom, tell you straight what's involved, and put it in writing. For the money side, our bathroom reno cost guide has the honest breakdown.