# Bathroom walls sweating?



## promax

Hey guys I have a customer that told me over the phone that his bathroom walls (that he is hiring me to repaint) have what looks like water streaks or water drip marks on them. I've seen this before in some bathrooms and always just cleaned the walls down well and painted 2 coats of eggshell or matte finish on it. Any ideas on what causes this and if there is a way to stop it completely by use of certain paints and primers. Would like to know an actual process on this one as opposed to just cleaning and slapping on 2 coats (oh and also praying i don't get an angry call about it after the fact lol) thanks for any info you guys have on this.


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## dvab

The cause is excessive moisture coupled with lack of ventilation. The phenomenon is caused by moisture condensing on the walls and extracting surfactants or other soluble compounds from the paint film. Though often referred to as surfactant leaching, these extracts are not always surfactants. Sometimes they can simply be washed off and will eventually leach out completely, other times, these extractives will permanently stain the surface. Some paints are more or less prone to doing it - try to go with a K&B type product since they are built for this environment.


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## The Paint Supplier

There are coatings out there that claim "no streaking". I would stick to a bathroom specific paint eggshell or higher. I have seen some testing done on the Zinsser Kitchen and Bath vs Muralo Nano Kote. The Nano Kote had no streaks. The only negative is that they don't come in the dark bases.

The Paint Supplier


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## HQP2005

HO needs an exhaust fan installed. If he has one already, tell him to leave it on for 30 minutes after showering with the door closed to vent out the excess moisture.


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## Schmidt & Co.

^^^What he said. Long hot showers cause condensation to form and run down the walls spotting the substrate. The solution is to marry my wife. From then on you will only take cold showers.


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## Builtmany

HQP2005 said:


> HO needs an exhaust fan installed. If he has one already, tell him to leave it on for 30 minutes after showering with the door closed to vent out the excess moisture.


I install push button timers for this exact use. That way the shower user can leave it on for 30 mins after exiting the room and it will turn itself off automatically.


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## Amish Elecvtrician

Let's look at the bigger picture ....

Others have correctly addressed the ventilation issue. There will never be a solution if the ventilation isn't fixed.

The simple fact is that the cheapest bath fans move enough air ONLY if there's a very short, straight exhaust duct made of rigid metal. Any other duct run requires a bigger fan.

Just as important is the fact that no fan can take air out, unless there is also a way for air to get in. If there isn't a vent in the door, the door ought to stop an inch or two above the floor.

Painters face a special problem in painting bathrooms: leaching. Moisture that sits atop paint will leach pigments out of the paint, then deposit those pigments when they dry. Since iron is one of the pigments, we end up with 'rust spots' on the ceiling.

With all the technology we have, it's still pretty hard to beat good, old fashioned shellac for moisture resistance. Perhaps we might want to make it 'standard' to apply a coat of shellac in bathrooms- especially the ceilings.


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## Oden

Schmidt & Co. said:


> ^^^What he said. Long hot showers cause condensation to form and run down the walls spotting the substrate. The solution is to marry my wife. From then on you will only take cold showers.[/Q
> 
> The problem is to marry my wife. She empties the water heater every single shower. Its like a sauna in there when she is done. Waterfalls run down the walls. I freshen it up with a roller periodically.


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## playedout6

Is it just me... or is the problem compounded if the said bathroom has had a K&B paint applied and it had and oil base paint on it a couple of coats previously? I hear of problems from people who have painted it themselves and they seem to have more problems with the wall runs . Sometime I tend to think the culprit is the lack of a proper Prime coat over the oil when it was converted previously to latex.


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