Why Do Bathroom Walls Sweat: How to Stop It


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Bathroom wall sweat is condensation from steamy shower air meeting cold air by the walls. Cold air holds less water than warm air, so droplets form on the walls. To mitigate or stop sweating, increase bathroom temperature, ensure adequate ventilation, use dehumidifiers, or lower water temperature or duration.

I hate having wet bathroom walls. Hanging towels up to dry becomes a fruitless endeavor because they just soak up the water droplets on the wall behind them. The little rivulets of water always attract dirt and make my bathroom look gross. And, whenever I’m about to go out somewhere fancy, I invariably brush up against the wall and get a patch of wet on my outfit (which never seems to dry before I arrive at my destination, but that’s a different mystery).

Finally, I had enough of living with sweaty bathroom walls and decided to do something about it. I know a fair amount about bathroom ventilation from working on this blog, so I suspected the excess water was somehow related to the functioning of my bathroom fan. I was right, which you will see below, but I also discovered some other factors that are involved, and, most importantly, how to address the problem sustainably.

The “Sweat” Is Condensation

Unlike humans, your bathroom walls do not have sweat glands that cause them to perspire. Instead, the “sweat” that appears is a result of condensation forming on the walls.

Condensation occurs when the warm, moisture-filled air (such as the steam that forms after a hot shower) comes into contact with colder and less moist air (such as the air surrounding the cold tiles/walls in your bathroom). The hot air will move down this temperature gradient (from hot to cold), causing the evaporated water, or steam, to return to its liquid form. It does this because colder air holds less moisture than warmer air.

bathroom fan dripping because of condensation

These water droplets will then attach to the surface of the bathroom walls, and drip down, which can create the appearance of the walls sweating. If these droplets are yellow or brown in color, you might also want to have a read through my article on Why Do Bathroom Walls Sweat Yellow/Brown.

Low Bathroom Temperature Promotes Condensation

Bathrooms are the common victims of wall sweating, and this is because their very essence and characteristics provide the necessary requirements for condensation to occur.

As I explained above, condensation occurs because hot, wet air comes into contact with air that is colder and drier, which causes the evaporated water to transform into liquid and drip down the wall.

When you have a hot bath or shower, steam (hot, moist air) is produced. Since most bathrooms have a low temperature due to the tiling, lack of soft furnishings, open windows, etc., they are prone to condensation.

temperature meter

Poor Ventilation Adds to Condensation

When your bathroom ventilation is inadequate, the result is a build-up of shower/bath steam in the room. Exhaust fans, open windows, and a variety of alternative, but often less effective, ventilation systems are designed to remove the steam-laden air from the bathroom.

The rate at which steam is produced will most likely exceed the rate at which it is removed, so you have to leave the fan running after the shower, but it will dissipate the steam more rapidly than would happen naturally (without deliberate ventilation).

Less steam means less condensation. Less time in the bathroom means less time to condense. As a result, poor ventilation results in sweating bathroom walls.

Should You Be Concerned About the Condensation?

Condensation will occur quite often in your bathroom, particularly if you make use of the facilities regularly. Whenever we talk or read about bathroom moisture-related problems, we automatically link it to the steam created by the shower. However, it is really the condensation of this steam—the droplets that form on the surfaces of the bathroom—that are of concern.

That being said, you don’t need to go into a complete anxious spiral after every shower when you notice water dripping down your walls. As long as you see that the sweat disappears fairly quickly (and it should if you have sufficient ventilation in your bathroom), then you don’t really need to be concerned as it is purely a result of hot air meeting cold air.

The biggest problem you could potentially have on your hands is dry water marks on your tiles or paint, which can easily be removed with a slightly damp cloth. By drying your walls after a shower, you can prevent these marks from appearing in the first place.

Water marks from the ceiling, water flows from the ceiling

However, if the water tends to stay dripping down the walls for quite a long time, perhaps for hours or even over night, then it is a cause for concern. If the water is not evaporating, it is a sign that your bathroom is too humid and becoming saturated with water.

The humidity will cause water to settle on your walls and ceilings, which can cause serious issues to develop. These are not only a nightmare to rectify structurally but also bring along health hazards.

4 Solutions to Sweating Bathroom Walls

Unfortunately, condensation is always going to become a problem in your bathroom. However, you can take steps to actively reduce the amount of condensation that forms and, therefore, reduce the appearance of sweating walls.

1. Increase the Bathroom Temperature

Since the process of condensation requires hot and cold air, and no one will give up their hot steamy showers for ice baths, the only logical conclusion would be to increase the bathroom’s overall temperature. By doing this, you reduce the temperature gradient, which will lower the chance of condensation happening. 

As most bathrooms are constructed with cold materials like tile and porcelain and replacing these with carpets and material wall hangings is wildly ill-advised, there are other ways you can increase the temperature of the room.

Bathroom floors are a huge source of cold, dry air, so addressing this first will make a world of difference. There is really only one solution for cold floors in a bathroom where you can’t lay plushy rugs: underfloor heating. This doesn’t just warm the tiles, however; the heat will rise throughout the whole bathroom, increasing the overall temperature.

SunTouch TapeMat Electric Under Floor Heating Kit with Command Touch Programmable Thermostat 120V, 2.0' x 15.0' (30 Sq. Ft.), Orange

Another way to make your bathroom warmer is to pre-heat it before you use the shower or bath. You can do this by placing a small portable heater (amazon link) in the room, and closing the door for about 30 minutes before you need to use it. The air will become significantly warmer, so the steam won’t be able to condense as much.

Don’t forget to remove the electric heater from the bathroom before you shower!

As an added bonus, when you increase the overall temperature of the bathroom, you also reduce fogging of your mirror.

2. Ensure Adequate Ventilation

We have already established that sweating walls are only a cause of concern when they do not dry quickly. In order to prevent this, you will need to speed up the drying process. This can be done by making sure there is sufficient ventilation in your bathroom. 

If there is enough airflow in and out of the bathroom, there is less chance for the air to become saturated and cause the bathroom to become humid.

Park Ridge Products VBHI3218PR VBHI Vinyl Basement Hopper Window, 32" x 18", White

Making sure you keep a window open while you shower, and even open the bathroom door for a couple of hours afterward is an easy and simple way to increase the ventilation in the bathroom. While windows are considered adequate bathroom ventilation, few people actually use it effectively, so I always recommend some kind of mechanical alternative.

If you have one, make sure that your bathroom fan is working properly at removing steam from the room. If it isn’t, you can expect a lot more condensation to form.

Additionally, make sure your bathroom fan has the appropriate CFM for the room so that it can adequately keep up with the required air changes.

3. Install a Dehumidifier

Another way to decrease the amount of condensation in your bathroom is to invest in a dehumidifier to help remove moisture from the bathroom. These are particularly helpful if you do not have a bathroom fan.

While dehumidifiers cannot ventilate a room (they do not remove and replace air, only extract the water from the existing air) they do reduce the amount of moisture in the air. Less moisture means less chance of the air being warm and wet.

SEAVON Dehumidifier Small Dehumidifiers for Home 2200 Cubic Feet (260 sq ft), Portable and Compact 27 oz Capacity Quiet Dehumidifiers for Basements, Bedroom, Bathroom, RV, Closet, Auto Shut Off

4. Reduce the Temperature of the Water

On the other side of the issue, you can decrease the temperature gradient by making sure that you are not producing as much warm, moist air. If you do this, then the air cannot condense and form water droplets on your walls. 

There is a simple way to achieve this: have a cooler shower. I know, I know, there is nothing quite like soaking the day away while the hot water beats down your back, but having colder showers will definitely help your condensation issue.

The air in your bathroom won’t be getting as warm, so it won’t be able to hold as much moisture. Less moisture means less condensation.

temperature knob being turned to high

If you simply can’t reduce the temperature of your showers, then try reduce the time in which you have them. This way you get your steamy oasis, but your bathroom has less steam to condense.

Sources

https://www.mirashowers.co.uk/blog/how-to/how-to-deal-with-bathroom-condensation/

https://runtalnorthamerica.com/why-is-my-bathroom-cold/#:~:text=2)%20Bathroom%20design%20is%20not%20conducive%20to%20%E2%80%9Cwarmth%E2%80%9D.&text=The%20room%20feels%20much%20cooler,than%20the%20air%20temperature%20typically.

https://www.thespruce.com/tips-for-a-toasty-warm-bathroom-326923

https://longhomeproducts.com/blog/house-wet-walls/

https://www.mirashowers.co.uk/blog/how-to/how-to-deal-with-bathroom-condensation/

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