Every Decision You Need to Make Before Your Bathroom Waterproofing (And Why It's Too Late After)

Every Decision You Need to Make Before Your Bathroom Waterproofing (And Why It's Too Late After)

Our bathroom hit waterproofing stage last week. Tiles start tomorrow. And standing in that room - membrane on every wall, every floor junction sealed, every penetration locked in — I was reminded of something I tell every renovation client: this is the point of no return.

Once waterproofing goes down, the decisions are made. Not by you sitting at your kitchen table with a coffee - by whoever showed up on site that day with whatever information they had. If your planning wasn't done before this moment, you're either paying to redo it or learning to live with it.

Here's every decision that had to be confirmed before our waterproofer started and why each one matters.

TAPWARE HEIGHTS

Every tap, mixer, and shower rose has a rough-in height - the point where the pipe comes out of the wall. That position is set before waterproofing and tiling. Change your mind afterward and you're cutting through waterproofing membrane, potentially compromising it, and paying a plumber to move a pipe that's already been set.

For our ensuite, we confirmed: shower rose height, hand shower rail position, bath spout height, and basin mixer rough-in. All confirmed in writing before a single drop of membrane went on.

WASTE LOCATIONS

Where your shower drain, bath waste, and basin waste sit is determined by your plumber before waterproofing. The floor is graded to fall toward the waste - change the waste location and the entire floor grade is wrong.

This is one of the most common and most expensive mistakes in bathroom renovations. Confirm your waste locations with your builder and plumber before waterproofing. Get it in writing.

SHOWER NICHE POSITION AND HEIGHT

A shower niche is built into the wall cavity before waterproofing. The position - height off the floor, which wall, how wide - is structural. Once waterproofing goes on and tiles go down, a niche can't be added or moved without demolishing tiled wall.

We confirmed: niche height (bottom of niche at 1200mm), niche width, and which wall. Done before waterproofing, not during.

SHOWER SCREEN LOCATION

Where your shower screen fixes to the wall and floor affects waterproofing detailing at that exact junction. Your waterproofer needs to know where the screen goes so they can correctly membrane around the fixing points. Confirm the screen type, size, and exact fixing location before waterproofing starts.

HEATED TOWEL RAIL POSITION

Heated towel rails that are hardwired need their electrical rough-in — the cable coming out of the wall - positioned before waterproofing. The location of that cable determines where your rail sits permanently. Move it after waterproofing and you're cutting wall membrane.

DOWNLIGHTS AND EXHAUST FAN LOCATIONS

Ceiling penetrations for downlights and exhaust fans need to be confirmed before any ceiling work, waterproofing, or lining goes on. Your electrician needs to know exactly where each fitting goes. Exhaust fans in particular need to be positioned correctly relative to your shower to do their job - this isn't a decision to make on the day.

VANITY POSITION

Where your vanity sits determines plumbing rough-in positions, tile set-out, and sometimes electrical outlet locations. If your vanity position shifts after waterproofing, your plumbing rough-ins are in the wrong place. Confirm the exact position - including clearances from walls and the toilet if relevant - before waterproofing.

TILE SET-OUT

This one surprises people. Your tiler needs to know the tile set-out before waterproofing because it affects where cuts fall, where grout lines land relative to fittings, and how the room reads visually. A good tiler will set out the room on paper first - confirming where full tiles fall and where cuts happen - before a single tile goes down. This conversation needs to happen before waterproofing, not after.

THE HONEST TRUTH ABOUT RENOVATION PLANNING

Every single one of these decisions seems manageable on its own. The problem is that in a real renovation, they all arrive at once - usually when your builder calls and needs an answer today because the waterproofer is booked for tomorrow.

That's not planning. That's reacting. And reactive decisions in a bathroom renovation cost money.

The way to avoid it is to have every single one of these decisions documented - confirmed, in writing, with your builder - before waterproofing stage arrives. Not scrambled together on a phone call the night before.

That's exactly what the Complete Renovation Planning Pack is built for. Every template you need to document your decisions - measurements, finishes, fixtures, fittings - so that when your builder calls, your answer is already written down.

 

Shop the Complete Renovation Planning Pack — $119.95

 

A CHECKLIST OF EVERY DECISION TO CONFIRM BEFORE WATERPROOFING

Save this. Send it to your builder. Confirm every single item before your waterproofer arrives.

  • Tapware heights — shower rose, hand shower, bath spout, basin mixer
  • Waste locations — shower drain, bath waste, basin waste
  • Shower niche — height, width, wall position
  • Shower screen — type, size, exact fixing location
  • Heated towel rail — position, hardwired or hydronic
  • Downlight locations — quantity, position in ceiling
  • Exhaust fan location — relative to shower, venting direction
  • Vanity position — exact placement, wall clearances
  • Tile set-out — confirmed with tiler before membrane goes on
  • Any other wall penetrations — soap niches, grab rails, mirror cabinet rough-ins

If you can't answer every item on this list confidently before your waterproofer arrives, your planning isn't done yet.

FAQ

What decisions need to be made before bathroom waterproofing? Tapware rough-in heights, waste locations, shower niche position, shower screen fixing points, heated towel rail position, downlight and exhaust fan locations, vanity placement, and tile set-out all need to be confirmed before waterproofing starts. These decisions are locked in once membrane is applied.

Can you move a shower drain after waterproofing? No. Moving a waste location after waterproofing requires cutting through the membrane, relevelling the floor grade, and redoing the waterproofing in that area. It's expensive and risks the integrity of the waterproofing system. Confirm waste locations before your plumber sets them.

What happens if you don't plan before waterproofing? Decisions get made on site by your builder or tradesperson with whatever information is available. This leads to tapware in the wrong position, niches in the wrong wall, and fittings that don't align with your tile set-out. Changes after waterproofing cost significantly more than getting it right the first time.

How do I prepare for bathroom waterproofing? Confirm every rough-in position with your plumber, every penetration with your electrician, your tile set-out with your tiler, and your fixture positions with your builder — all in writing — before the waterproofer arrives. Use a planning template to make sure nothing gets missed.

 

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