Why an Open Walk-In Shower Can Keep Wetting the Vanity
Open walk-in showers are one of those bathroom ideas that look almost effortless in photographs.
A fixed glass panel rises from the floor. There is no door, no bulky frame and very little hardware. The shower seems to blend into the room rather than occupying a separate enclosure.
Then the renovation reaches the practical stage and someone asks the question that should probably have been asked much earlier:
Will water actually stay inside it?
More specifically, if the vanity is only a short distance from the open end of the shower, will its side panel be wet after every use?
This is where the usual advice becomes frustrating. Search online and you will quickly find rules such as “900 mm glass is enough” or “make the screen at least 1000 mm”.
Those numbers sound useful because they are simple.
They are also unreliable.
A 900 mm panel can work extremely well in one bathroom. A 1200 mm panel can still allow significant splash in another.
The missing measurement is not simply the size of the glass.
It is the relationship between the shower head, the person using it, the open edge of the screen and whatever sits outside that opening.
That is where walk-in shower design really begins.
The Glass Is Not the Source of the Splash
A floor plan usually represents a shower as a rectangle with a line of glass along one side.
That is useful for measuring the room, but it hides what happens when someone actually turns the shower on.
Water does not simply fall vertically from the shower head to the drain.
It hits a person first.
Shoulders, arms, hair and hands redirect it sideways. Someone washing their hair creates a different splash pattern from someone standing still under a rain head. A hand shower used to rinse the walls can send water in directions that never occur during an ordinary shower.
For this reason, I find it more useful to think of the person as part of the water source.
Imagine a 1600 mm-long shower with a 1000 mm fixed screen.
On the drawing, that sounds generous.
Now imagine the shower head is positioned so that the user naturally stands only 100–150 mm behind the open edge of the glass.
Most of the panel is technically “long enough”, but almost none of it extends beyond the main splash source.
Water hitting the user's shoulder has a relatively clear path out of the opening.
Move the shower head deeper into the enclosure and the same 1000 mm panel can behave very differently.
The glass has not changed.
The geometry has.
This is why the more useful measurement is often:
How far does the screen extend beyond the user's normal showering position?
That number tells you much more than the overall screen length.
Why the Vanity Is Often the Fixture That Suffers
A few droplets escaping a walk-in shower are not necessarily a problem.
What matters is where they land.
If the opening faces a tiled circulation area, escaped water may be easy to wipe and relatively harmless.
If the opening points directly toward a vanity 200 or 300 mm away, the consequences are different.
Bathroom cabinetry is designed to live in a humid environment, but there is a distinction between bathroom humidity and direct shower spray every day.
The vulnerable areas are often not the obvious surfaces.
They can be:
the lower edge of a side panel;
the underside of a cabinet;
a plinth;
an exposed join;
a cut edge around plumbing;
the small junction between cabinet and floor.
If water repeatedly reaches those places and is slow to dry, a cabinet can begin showing swelling or edge deterioration long before the front face looks damaged.
This is one reason I am cautious about layouts where the open end of the shower points directly at the vanity.
The question is not simply:
Can water escape?
Some probably will.
The better question is:
What have we placed in the path of the water that escapes?
Sometimes rotating the shower entry by 90 degrees is more effective than adding another 200 mm of glass.
That is a much cheaper decision to make on a drawing than after the vanity, waterproofing and glass are already installed.
Floor Fall Cannot Fix Airborne Splash
This is another point that gets mixed up surprisingly often.
A homeowner may look at a walk-in shower design and say:
“The floor falls back to the drain, so it should be fine.”
The floor fall is important.
But it solves a different problem.
It controls water after the water has reached the floor.
It cannot stop a droplet that leaves a user's shoulder, passes through the open side of the shower and lands halfway up a vanity panel.
There are really two systems operating at the same time.
The first is splash containment.
That is controlled by:
shower-head location;
user position;
screen geometry;
opening direction;
glass configuration.
The second is drainage.
That is controlled by:
floor falls;
thresholds;
drain location;
finished levels.
A bathroom can have excellent drainage and poor splash containment.
It can also have very good glass containment but poor drainage outside the screen.
Treating those as separate questions makes the layout much easier to evaluate.
This distinction is particularly important with linear drains. A large linear drain may make the shower look capable of handling huge volumes of water, but it cannot collect water that has landed outside the part of the floor that falls toward it.
The drain is not a substitute for a barrier.
Why One Homeowner's “900 mm Is Fine” Is Almost Meaningless
Walk-in shower discussions often become collections of personal measurements.
“My screen is 900 mm and the floor stays dry.”
“Ours is 1200 mm and water still gets everywhere.”
Neither homeowner is necessarily wrong.
Their bathrooms may simply be different.
Suppose Bathroom A has:
a 900 mm fixed screen;
a rain head set well back from the opening;
the user standing 500 mm behind the screen edge;
the vanity behind the protected side of the glass.
Now consider Bathroom B:
a 1200 mm fixed screen;
angled shower head much closer to the opening;
user standing almost level with the glass edge;
vanity directly beyond the opening.
Bathroom B has more glass.
It can still perform worse.
That is why I would not choose a screen length from another person's bathroom without also knowing where their shower head and nearby fixtures are.
The number is missing the context that gives it meaning.
The Hand Shower Is the Test People Forget
A shower can perform perfectly during normal use and still soak the rest of the room once a week.
The reason is usually the hand shower.
During an ordinary shower, the spray pattern may be predictable.
During cleaning, someone may use the hand shower to rinse:
the glass;
tiled walls;
the shower floor;
niches.
The spray is now being deliberately aimed around the enclosure.
If the open end faces a vanity, water may reach it very easily.
The same issue appears in family bathrooms.
A parent washing a child or a child holding the hand shower creates a very different water pattern from an adult standing underneath a fixed rain head.
This does not mean open showers are unsuitable for family bathrooms.
It means the design needs to acknowledge how the shower will actually be used.
A layout that only works while one adult stands perfectly still beneath an overhead head is not necessarily a robust layout.
The Awkward 80 mm Gap
One of the worst arrangements is often not a large gap.
It is the tiny one.
Imagine the fixed shower screen ends, then there is an 80 mm gap, then the vanity begins.
Water gets into that slot.
Hair gets into that slot.
Dust gets into that slot.
But your hand, mop and vacuum attachment barely do.
The result can be a permanently annoying strip that receives water and is difficult to clean.
From a design point of view, I would rather see a gap that is deliberately:
wide enough to clean;
or
properly resolved as a junction,
than a narrow leftover space created because two products happened to fit numerically.
This is another reason “everything fits on the floor plan” is not enough.
Usability includes the space around the products.
When More Glass Actually Helps
There are situations where extending the fixed panel is the obvious answer.
If the user is standing close to the open edge and the entry is still comfortably wide, more glass can move the opening farther away from the main splash zone.
But extending the main panel is not the only option.
A short return panel can sometimes interrupt the water path more effectively because it changes the direction of the opening.
A hinged flipper panel can provide additional containment during use while preserving more entry width when it is folded away.
A full door provides stronger containment again, although it changes the character of the shower completely.
Each solution exchanges something:
more containment
for some combination of:
reduced openness;
extra hardware;
more cleaning;
narrower entry.
That trade-off is more useful to understand than deciding that a doorless shower is inherently better.
The Best Fix May Be Moving the Shower Head
This is the part I would look at before adding hardware.
If the renovation is still at rough-in stage, moving the shower outlet deeper into the shower may change the splash geometry substantially.
Imagine shifting the user's normal standing position 250 mm farther behind the edge of the fixed glass.
That extra 250 mm of protected distance may be more useful than adding 250 mm to the glass at the other end.
Of course, whether the shower head can be moved depends on:
framing;
plumbing;
mixer configuration;
shower size.
But this illustrates an important renovation principle:
Do not solve every splash problem with more glass. Sometimes the water source is in the wrong place.
By the time the bathroom is tiled, that option may no longer be practical.
Which is why this conversation belongs early in the project.
Open Showers Also Feel Different in Winter
Water containment is not the only thing the missing door changes.
An open entry also allows more air movement around the person showering.
In a warm bathroom that may barely be noticeable.
In a cold bathroom, especially in winter, the difference can be significant.
Warm water heats the skin while cooler room air moves across the wet body.
Some users experience this as a persistent cold draught.
The bigger and more open the shower, the more important the room's heating strategy becomes.
This is another example of why a walk-in shower should not be evaluated only through photographs.
The photo shows:
glass;
tiles;
hardware.
It does not show:
moving air;
surface temperature;
user comfort.
A Simple Test I Would Do Before Finalising the Layout
Take the bathroom floor plan.
Forget the screen length for a moment.
Mark four things.
First: the shower head.
Second: where the person will normally stand.
Third: the open edge of the glass.
Fourth: the nearest moisture-sensitive item outside the shower.
Now look at the line from the user toward that item.
If the vanity is sitting directly beyond the open edge with no meaningful barrier, that deserves attention before anything is built.
Then ask:
Could the shower head move deeper?
Could the opening face another direction?
Could the vanity move behind the glass line?
Would a short return panel solve the problem?
Is the gap beside the vanity actually cleanable?
This is not a hydraulic model.
It does not predict exactly where every droplet will land.
It does something more practical:
it exposes obviously vulnerable layouts before they become expensive.
A Representative Renovation Scenario
Consider a 1600 mm-long walk-in shower.
The designer specifies a 1000 mm fixed screen.
The vanity is positioned about 250 mm beyond the open end.
On the drawing, the screen appears substantial.
During installation, the rain head is placed relatively close to the front because that location works neatly with the plumbing.
The user now stands near the end of the fixed panel.
Once the shower is used, water bouncing from the user's arms and shoulders passes through the opening and reaches the side of the vanity.
The original question had been:
Is 1000 mm enough glass?
The glass was never really the problem.
The problem was the relationship between:
where the water was being generated
and
where the glass stopped.
The same room could potentially have performed better with:
the shower head farther back;
the opening rotated;
the vanity moved to the protected side;
a short return panel.
Those decisions are easy before waterproofing.
They are much less convenient afterwards.
Before You Commit to the Open Side
An open walk-in shower deserves a quick reality check before rough-in and waterproofing are finalised.
Confirm where the user will actually stand, not just where the shower head appears on the product drawing. Look from that position toward the open edge.
Then check what is immediately outside it.
If it is:
tiled wall;
generous open floor;
the layout has more tolerance.
If it is:
vanity cabinetry;
toilet paper;
towels;
timber joinery;
the design should be less forgiving of escaped spray.
Also test the shower in “non-standard” use:
hand-shower rinsing;
cleaning;
children;
two-person use if relevant.
Finally, look at the floor separately.
Ask where escaped water travels after it lands, because good splash geometry and good drainage still need to work together.
Final Thought
A good walk-in shower is not one that contains every molecule of water.
That is an unrealistic standard for an intentionally open enclosure.
A good design controls enough of the water that the remaining splash lands somewhere the bathroom is designed to tolerate.
That distinction matters.
The goal should not be:
“How do I stop absolutely all water leaving the shower?”
It should be:
“How do I make sure the water that does escape cannot create an everyday problem?”
That is why the most important line on a walk-in shower drawing is not necessarily the length of the glass.
It is the invisible line between the person under the water and the things outside the shower that need to stay dry.
Design that relationship first.
Then decide how much glass you actually need.
Sources and Further Reading
MBIE — E3 Internal Moisture
New Zealand Building Code guidance relating to managing moisture within buildings.
https://www.building.govt.nz/building-code-compliance/e-moisture/e3-internal-moisture
MBIE / CodeHub — E3/AS2 Internal Moisture
Acceptable Solution relating to internal wet-area moisture management.
https://codehub.building.govt.nz/resources/e3as2-first-edition