Never Pour Water on a Bathroom Floor in New Zealand

We were called to a first floor bathroom in Hobsonville where water had run across the floor, out past the door, and through to the ceiling below. The owner expected us to find a burst pipe.

Nothing was leaking. The floor had been cleaned by tipping water over it.

This catches people out constantly, and almost always people who have lived somewhere the practice is completely normal. So it is worth explaining what is actually different here, because it is not obvious by looking.

Why can you not wash a bathroom floor here?

In much of the world a bathroom is a wet room. The entire floor is tanked, it is laid to fall towards a floor drain, and hosing it down is exactly what it was built for. Water on the floor is the design working.

A New Zealand bathroom is not built that way. Only the shower is treated as a wet area: that is where the waterproofing goes and that is the only part laid to fall. The rest of the floor is a finished surface, not a waterproof tray. It is flat, its edges meet the wall linings and the door threshold, and it has nowhere to send water.

So water poured on a New Zealand bathroom floor does not drain away. It sits, spreads to the lowest edge, which is usually the doorway, and soaks into the junctions it finds on the way.

But my bathroom has a drain in the floor

Many do not have one at all. Where there is one, it is an emergency overflow, not a floor drain.

It is there so that if a cistern splits or a hose lets go, some of the water leaves rather than all of it going through the ceiling. That is a very different job from draining a washed floor. The floor is not graded towards it, so water only reaches it if it happens to be standing in the right spot, and everywhere else it goes wherever gravity takes it.

Seeing a grate in the floor is not permission to pour water on it.

So how am I supposed to clean it?

Normally, and it is easier than what people are doing.

A spray cleaner and a cloth is completely fine. There is nothing wrong with the bottle of bathroom spray under your sink, and the products are not the problem. So is a mop, as long as it is damp and well wrung out, not dripping.

What causes the damage is volume: a bucket tipped over the floor, a hose, a jug, filling the floor and squeegeeing it towards the door. That is the practice to drop.

Water sitting across a tiled bathroom floor with nowhere to drain

Where does the water actually go?

Into the joins, and then into the building.

Grout is not waterproof. Neither is the silicone line where the tiles meet the wall once it is a few years old, and neither is the gap under the door threshold. Standing water finds all three, gets under the floor covering and into the framing, and then follows the framing downwards.

At the Hobsonville job it came out through the ceiling of the room below. Once we had the trim and the flooring up at the doorway, the underlay and the carpet beyond it were wet as well, and the framing had taken water. That job needed drying equipment run in the affected rooms, which is a restoration job rather than a plumbing repair.

Flooring lifted at the bathroom doorway, showing wet underlay and framing beyond

What if the floor is cork, timber or vinyl?

Worse, and faster.

Cork and timber swell at the joints and lift, and they do not go back down. We attended a property in Mairangi Bay where water marks kept appearing around the toilet and into the garage, and the cause turned out to be the same thing: the floor was cork and the tenant had been washing it down. There was no plumbing fault to fix. The advice was to stop wetting the floor and clean it with a well wrung cloth instead.

Vinyl looks like it should be fine because the sheet itself is waterproof, but water runs off the edges and under it through the seams and the perimeter, and then it sits there in the dark against the substrate.

I rent, or I manage the property

This one matters, because it is a genuinely common cause of avoidable damage in rentals and it is almost always well intentioned. Somebody is trying to keep the bathroom clean.

If you manage properties, it is worth saying at the start of a tenancy that bathroom floors are cleaned with a damp mop or cloth, not washed down. It takes a sentence, and it prevents a claim that involves ceilings, carpet and drying gear.

If you are a tenant and you have been doing it, stop now and tell the property manager if you have seen any marking. Early is a conversation. Late is a ceiling.

Drying equipment running in a room after water damage from a washed bathroom floor

How do I know if I have already done damage?

Look at the edges rather than the middle of the floor.

The door threshold or the bottom of the architrave swollen, soft or discoloured
Skirting boards lifting or bubbling, particularly on the doorway side
Vinyl or tiles lifting at the perimeter, or grout that stays dark long after everything else has dried
A stain on the ceiling of the room below
A musty smell in the bathroom or the room next to it that does not clear

If you can see any of those, send us a photo. It is far cheaper to check than to find out through the ceiling.

Common questions

Are bathroom cleaning sprays bad for the plumbing?

No. Normal spray cleaners used on a cloth are fine, and we are not asking anyone to stop cleaning their bathroom. The issue is the amount of free water on the floor, not what is dissolved in it. Drain cleaning products are a separate question, and those are worth being careful with, but ordinary bathroom spray on a surface is not what causes these jobs.

Why did the builder not waterproof the whole floor?

Because it is not what the building is designed around here, and doing it properly means grading the entire floor to a drain, which changes the floor build up, the door heights and how the room connects to the rest of the house. Waterproofing the shower area is what the work is scoped to. It is not a shortcut, it is a different kind of bathroom.

Can I have a wet room built in New Zealand?

Yes, and they are becoming more common in new builds and renovations. It has to be designed as one from the start: the whole floor tanked, laid to fall to a drain, with the right junctions at the doorway and the right substrate underneath. What you cannot do is treat an ordinary bathroom as though it were one. If you want a floor you can hose down, tell your designer before the bathroom is built, not after.

The water only reached the doorway. Is that really a problem?

The doorway is the worst place for it to reach. That is where the waterproofing stops, where the floor covering is cut, and where the framing under the threshold is exposed to whatever gets in. Water pooling in the middle of a tiled floor and mopped up quickly does very little. Water that made it to the door has already gone somewhere you cannot see.

Is this covered by insurance?

Often not, and that is worth knowing before it happens. Damage from repeatedly washing a floor is neither sudden nor accidental, and it accumulates over months, which is the definition of gradual damage in most policies. A one off flood from a burst hose is a much easier claim than a bathroom floor that has been washed down every week for a year.