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Another Vapor Barrier Thread


psustang89's Avatar
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01-13-12, 04:46 AM   #1  
Another Vapor Barrier Thread

There are many vapor barrier threads out there, but I think my situation is a little different than most.

My house was built in the 40's, very little insulation, no french drains, etc. There is still a room in the corner of the basement with a dirt floor; the old coal sellar. I plan to pour the floor and frame the room as a laundry room (wood 2x4 framing, drop ceiling). The rest of the basement will remain bare concrete block walls. The walls do get damp, but in 8 yrs I have never had water on the floor of the basement.

The question: given my senario, do I need A) insulation behind the drywall of the new laundry room and B) where should the vapor barrier go.

Thanks for the help!

 
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Bud9051's Avatar
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01-13-12, 06:17 AM   #2  
Hi 89, if you have been reading then you know where the answer is going to start, eliminate the moisture at its source. Here is one of the problems. You know the wall gets damp, but it really doesn't get that damp. Not quite. Even walls that look dry can be passing gallons of water per day, it is just evaporating before you can see it. In your case, enough is passing through that you can see it, thus certainly many gallons are going into the air. If you block that evaporation, the moisture/water is still going to be coming through, but now it can't evaporate, it builds up behind your vapor barrier. Water will continue to push through until the inside is as wet as the outside, a law of physics. That is why sealers painted on the inside of a foundation wall most often fail, because the water pressure just builds and builds trying to equalize with the outside.

Now, the problem gets worse. In our modern age of improving the energy performance of our homes, the first step is to reduce the air leakage. But in your case, that is where all of this moisture is going. Tighten up the home, you or the next owner, and without knowing, those walls might start growing mold. Basements are perhaps the most difficult area to renovate because most were built long before moisture control measures were part of the construction process. Even homes being built today, often they will short change the life of the building by eliminating the water resistant barriers we now know are necessary.

Can you back up and do it right? I doubt you would want to spend that kind of money. What should you do? IMO, leave those exterior basement walls looking just like basement walls and control the humidity with a dehumidifier. Here's a thought. Have you seen those imitation bricks they paint onto concrete driveways. Have one brick wall and three others done as you like, and no moisture trapped where it can become a problem.

Bud

 
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01-13-12, 06:25 AM   #3  
Make sure you get a moisture barrier under the slab when you pour it in the room, the dirt floor could be adding a lot of moisture to the house.

 
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01-13-12, 07:52 AM   #4  
Thanks for the help. Based on your responses, it seems that my best, most cost effective plan will be to add a moisture barrier under the new slab (plastic I'm assuming) and leaving the 2 exterior walls as bare block. I only planned to frame with dry wall to dress up the room, so this isn't a major problem. Although the drop ceiling may look awkward butted up against the bare block, not sure.

Thanks again

 
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01-13-12, 08:01 AM   #5  
Do the floor first and then see whether the walls still get damp. That said, you may be best served leaving them bare but it's too soon to say. Personally, I wouldn't put in the ceiling either but I don't feel the need to dress up a utility room.

 
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01-13-12, 10:21 AM   #6  
Here is some reading to confuse you further . Just remember, all basements are different so not all advice applies to yours. My main concern is that you already know you have a moisture problem and finishing those walls is not going to make it better. That said, you can finish the above ground areas and even down a bit below to apply some rigid insulation and give you a matching area for your drop ceiling. Any moisture behind that first foot of below grade concrete will be able to escape to the inside below the one foot mark. Just a thought.
http://www.eere.energy.gov/buildings...s/db/35017.pdf

Bud

 
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01-15-12, 11:06 AM   #7  
As a laundry room you will be adding quite a lot of water vapor from time to time, but I imagine that neither you or your family will be living down there?
If this is the case, then all of the time you can have ventilation.
Any damp that finds its way from the walls or washing will continue to escape outwards as it does at present.
Ignore ideas of trying to block or divert the water vapor, these will only lead to trouble.

 
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