Sign In to join the community | Help
Build & Remodel


Wet walls and mold buildup-HELP!

Have been dealing with this issue for years now.  Our bedroom walls and living room walls get cold, wet, and black mold builds every winter.  Its frustrating cause I have our beds next to the walls.  I clean them off but this seems crazy to have to do this every winter.  We put cement next to some wall on the exterior ground and put some type of mesh barrier on other exterior ground areas.  I was gonna put insulation in walls but don't know if that would help. Please help.

Not what you were looking for ? Try posting a question
Posted 2013-01-31T22:00:52+0000  by mexicube mexicube


I would not deny the possibility that there might be structural problems in this house, but from the limited information supplied, it is quite possible that the mildew is the result of internal factors such as excess humidity, underinsulated walls, house temperatures kept too cool with resultant high relative humidity and little air movement. At a minimum, get a hygrometer to get an actual reading. Readings of significantly over 40% starts begging problems, especially if this a very cold climate.


What condition are the windows in? Do they sweat a lot? Is the woodwork and drywall in good shape around them?


If the house is early 1970's, the wall insulation may be minimal. If it is pre-WW2, the insulation may be totally lacking! It might be informative to cut a small observation hole in the wall down where the mildew is prevalent. Does the mold seem limited to the living side of the drywall or plaster, or are there signs of it in the wall cavity. This will also show positively how much insulation, if any, is present.


I agree with Steel Toes, more information and a few pics would be helpful.

Best Answer

Posted 2013-02-06T05:28:43+0000  by ordjen




I have often seen this situation in older homes where the insulation is not up to present standards.

the exterior walls get very cool and condensation forms on them, especially behind beds and dressers where no air is moving and they are shielded from the rooms heat.


Bedrooms tend to be relatively humid areas. Two people sleeping with the doors closed can generate alot of humidity. Add to this that most people turn the heat down at night while sleeping. As the heat goes down, the relative humidity goes up and then moisture condenses on the cool walls.


Try keeping your beds and dressers just a little away from the walls to allow air to circulate back there. Anything that keeps air moving will help, such as letting the furnace fan trun or having a ceiling fan running slowly. Keeping the house heat up keeps the relative humidity down.


Before you paint, make sure you first kill all the adtive mildew with a bleach solution. Be careful, bleach will also bleach carpeting! Paint only with a high quality paint such as Behr's Ultra. Ultra is inherently mildew resistant due to its nano technology, but all Behr paints also contain a chemical mildecide.


Of course, the walls can also be built out and insulated better, but this is considerable expense and mess. Try the lesser meathods first.


After painting, you might also try misting the area with Concrobium. This is a clear, odorless , harmless spray which will sit on the surface of the paint and help prevent mildew from returning. This is available in the paint department at Home Depot.


Hope this has helped

Posted 2013-02-01T17:04:42+0000  by ordjen

Hi mexicube,


What type of siding do you have on the outside?


Is this home over the crawlspace?


Do you think you can post some pictures of the walls and present mold and mildew?


I have to, on this part, disagree on this one with ordjen. If you’re getting mold and mildew over the bedroom and living room walls, it is time to get this immediately corrected. Are bedroom and living room walls on the same side of the house?


But first tell us a little bit more about your home?


What type of heating do you have and where is it located?


Your location (zip only)?



Posted 2013-02-05T19:59:30+0000  by George_HD_CHI

The house was made in the 50's.  The living room walls are in the front of the house.  The kids bedroom walls is on the same side as the living room.  Our bedroom walls are in the back oposite side.  The windows do sweat a lot.  Don't know how to post pictures but I did take some if you can help me figure that out.


Thank you,



Posted 2013-02-12T22:25:43+0000  by mexicube

I don't have siding on the house and am pretty sure its stucco.  We have a wall heater that is located in the hallway. The master bedroom walls are on different side of house that living room and kids room. My zip is 95204.  I took pics but dont know how to post.

Posted 2013-02-12T22:29:35+0000  by mexicube




To post a picture: when you write your comments in the window, you will see several icons above your text. Click on the icon  second to the right of the sunny face. I  am not sure what it is supposed to be, but when you click on it, a browse window will open which will let you post any picture that is on your computer.


Have you bought a hygrometer ( moisture meter) yet.? They are not very expensive. My guess is that it is going to show relative humidity in the 60's or above. That is TOO much humidity.


If you have a 50's house, you probably don't have insulated glass windows. Excess humidity will make them sweat to the point that water will pool on the sill; Storm windows would help cure this.


Do your bathrooms have effective exhaust fans? Or fans at all?


Does your cooking range have a vent? Cooking is a major sourse of humidity.


Does your laundry have an exhaust fan? Another major source , especially in a family with lots of kids generating multiple wash loads.


Is your house built on a crawl space that has no vapor barrier on the ground?


I am not sure how temperate Stockton, California is. The colder the climate, the more problems with moisture.


Just a few thoughts of what could be increasing moisture in your house. One thing for sure, mildew does not exist in dry environments. Get rid of the moisture, and the mildew will cease.

Posted 2013-02-13T00:35:20+0000  by ordjen

I havent bought a hygrometer yet.  So you think getting proper windows installed could be the solution?  I also wanted to mention that I noticed the walls get very cold in the winter and very hot in the winter.  I don't have exhaust fans.  I have a vent above the range stove. Dont know if the house is above a crawl space.  The house is right on the ground.  The mildew has been worse this winter because its been much colder this winter.

Posted 2013-02-13T17:44:34+0000  by mexicube

correction to my prior post.  The walls get very cold in the winter and hot in the summer.  Also, I attached a couple of pics.  Hope you can see them.

Posted 2013-02-13T17:47:14+0000  by mexicube




I don't thnk new windows will solve your problem, sweating windows  are merely a symptom of what is happening. If I am correct that your humidity in the house is too high, you must take efforts to bring it down. Proper exhaust venting is important. Trying to limit the amount of moisture being generated might also help.


It does sound like you don't have sufficient insulation in your walls. Unfortuantely, there is no easy, inexpensive cure for this. Insulation can be retro-fitted, but it is not cheap. You might want to get professional advice from an insulation company. When the walls are cold, moisture will condence on them. It might not be visible as wetness, but is sufficiently moist to support mildew growth.


You apparently do not have central heating, but rather a centrally located wall heater.  Central heating by its nature circulates the air in the house and equalizes moisture concentrations throughout the house. Keeping the house warmer and keeping the air moving will help control mildew. If the rooms have air moving, the cold surfaces will not let condenced moisture form. Slow moving ceiling fans would also help prevent condensation build-up.


It is by design that when a house has central heat, that the vents are always placed along the outside walls and usually under the windows. This washes the cold walls with warm, dryer air, making the room more comfortable and also controlling condensation on exterior walls.


In my paint contracting days in Chicago, I frequently had to deal with such condesation while painting. Latex paints are mostly water. Suddenly putting several gallons of paint on the walls dramatically raises the relative humidity. Most of the time this was not a problem, but when in was very cold outside, moisture would start to form on cold outside walls. To counter this, I carried box fans in my truck to keep the air moving, especially against the cold, outside walls.

Posted 2013-02-13T18:46:53+0000  by ordjen

Hello again,


Thank you for all the advice so far.  What can I do right now until I find the right insulation option?  The walls in my bedroom are wet.  I've moved some furniture but cant move my bed since the room is not big enough.  I open windows in the bathroom, bedrooms, living room as often as cold weather permits. 

Posted 2013-02-13T19:08:41+0000  by mexicube
Not what you were looking for ? Try posting a question