Sealing concrete basement floor


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Old 06-24-15, 12:56 PM
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Sealing concrete basement floor

I am looking into sealing my concrete basement floor. Water isn't really a problem, I am mainly concerned about odor. The basement was quite musty and much of the scent disappeared when I pulled out all the old nasty cat hair covered carpet and laminate/underlayment. I still sneeze a bit while working down there though and would like to seal the floor and reduce odor as much as possible before I put down new laminate.

I am wondering if I should get an actual penetrating/epoxy/oil sealer on the floor or if something like original kilz would be good enough. If would probably prefer putting down some sort of waterproofing sealer that's meant for basement floors if it handles odor as well. I'm not really sure what to get though. Preferably something I can find at Walmart or Lowes. Any suggestions?

Thanks
 
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Old 06-24-15, 01:32 PM
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Welcome to the forums.

What's the cause of the odor?
 
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Old 06-24-15, 01:44 PM
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Thanks. I think the old dirty carpet was a big part of it, but also the basement door had a rotted out threshold which I have since removed and will be replacing. It allowed the laminate's underlayment in front of it to get wet often. After that was removed I noticed a big difference in odor. I have a HEPA filter running and a fan in front of the door trying to get as much of the odor out as possible. I just wanted to be extra cautious and seal the floor to keep out any odor that could be coming from it. I am not aware of having any allergies, but I still get a little sniffly down there. As you can see I am not 100% sure. It just smells like a musty basement to me. I am just hoping sealing the basement will help a bit.
 
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Old 06-24-15, 02:07 PM
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Musty basements are usually caused by mold and mildew, which are in turn a result of moisture issues. That moisture doesn't have to be visible water, it can and most frequently is, moisture vapor. Unfortunately, treating the floor will not prevent it. The solution is most often a case of managing it. You start by measuring the humidity down there and then running a dehumidifier until the temperature adjusted RH is below 40%.

Is this a finished basement, walls and ceiling? Are the walls insulated?

Bud
 
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Old 06-24-15, 02:14 PM
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Since you mention the odor I suspect you may have water vapor coming up through the concrete. An easy test is to take a piece of plastic or even a garbage bag and smooth it out flat on the floor. Then tape all the edges down. Then in a few days pull up the plastic and see if the under side or concrete is wet. It's good to test in several areas around the space. If you do find water you'll have to be more cautious with how you treat the floor.
 
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Old 06-24-15, 02:19 PM
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Yes, it was fully finished when I moved in with exception of a utility room which is insulated with no drywall. The only thing I have removed was the flooring. I thought I read somewhere that concrete is porous and can let in moisture and sealing can help reduce that. Is that not correct? I will see If I can get a tool to measure the humidity level down there.
 
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Old 06-24-15, 02:24 PM
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Since you mention the odor I suspect you may have water vapor coming up through the concrete. An easy test is to take a piece of plastic or even a garbage bag and smooth it out flat on the floor. Then tape all the edges down. Then in a few days pull up the plastic and see if the under side or concrete is wet. It's good to test in several areas around the space. If you do find water you'll have to be more cautious with how you treat the floor.
I will give that a try. I did have a blue tarp on the concrete for the past few months and didn't notice any water on it or the floor when I pulled it up a few days ago. It wasn't taped down though.
 
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Old 06-24-15, 02:37 PM
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In the utility room where the walls are insulated but no drywall, how was it insulated? Did they install vertical studs and then add fiberglass insulation between the studs? Is there a vapor barrier under or over the fiberglass insulation?

Bud
 
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Old 06-24-15, 02:59 PM
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I don't think there is any barrier other than the insulation. This is what is looks like.
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Last edited by stickshift; 06-26-15 at 08:23 AM. Reason: Removed quoting of entire post
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Old 06-24-15, 03:26 PM
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That insulation is called "blanket insulation" with the less than flattering nick name of "the Diaper".
Photo #3 in the link below. The reason that musty small has become synonymous with basements is because they have been building them wrong for so long. Maybe not wrong, it is just that basements were originally intended to simply hold up our homes. I has been our fault for deciding all that space is too good to waste, but unfortunately it is poorly prepared to become quality living space. New homes can be built with dry basements, but existing homes are almost beyond being dry.

In your case it is the musty small that gives us a hint that something is wrong and unfortunately it is probably more than leftover odors from that carpet you removed. I always find it troubling to offer up difficult news, but the link I referenced will help explain. My approach would start by removing some of that blanket insulation shown in the picture to see how it is performing. I would then look for a place to see if that same insulation is behind the existing drywall. Then, that same link explains how to build and insulate a basement wall. Beyond providing the information, what you decide to do will be up to you.

Best
Bud
BSD-103: Understanding Basements — Building Science Information
 
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Old 06-24-15, 07:47 PM
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I checked behind the insulation in a number of places in the utility room and did not see any signs of mold/mildew/moisture. The concrete looked dry without any stains and the insulation was not discolored at all. There was one part I couldn't check due to junk in the way, but I will try to move it all tomorrow and give that a look. Could the french drain cause a musty scent? Its not 100% sealed as there are holes in the cover.

I bought a dehumidifier and will be running it all night in the utility room. Humidity was in the high 60s.

Ill try a few places behind drywall tomorrow. I don't want to patch many holes though.
 
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Old 06-25-15, 06:01 PM
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Found some issues today. Much of the basement walls are actually above the ground. I'm not sure why I didn't think of that earlier. I live on the slope of a hill. Anyway, the sections above the poured concrete/blanket insulation do appear to have water issues. This is right where the deck meets the house. I even found some white mold in there. The board on the deck side has turned green in the crack. As a bonus, apparently my hot water tank appears to be leaking and made a puddle in a section of the utility room I don't go often.
I'm a little scared about the location of where the water issue is...
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Where the deck meets the house. I think water sits in the crack where it turned green.

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Wider angle view of where the deck meets the house


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Something growing under the deck

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Just under the deck

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Another view under the deck. Water will actually sit at the base of the wall and it does appear like there has been water on inside in the past adjacent to this section.

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One of the notches just below the first floor of the house and above the poured concrete wall. The deck on the outside meets right around here and it appears to have places that have been wet previously

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Similar to above, just another section

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A whitish mold in another section

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Puddle under water heater complete with dead mouse
 
 

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