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Old 02-19-2009, 12:06 PM   #1
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Do I need to remove this?


Beginning my basement framing project...do I need to remove this half-insulated wall that already exists or can I build my new walls/framing in front of it?



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Old 02-19-2009, 12:13 PM   #2
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Do I need to remove this?


might be the picture, but it looks like moisture already got to the insulation. If so I would remove it and only use rigid or spray insulation in a basement.

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Old 02-19-2009, 12:14 PM   #3
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Do I need to remove this?


Are you talking about the black stains? I got some waterproofers to check it out, its just dust/soot (theres a chimney above there in the pic). There were some leaks but those are being repaired.
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Old 02-19-2009, 12:18 PM   #4
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Do I need to remove this?


More insulation is never a problem, a 2nd vapor barrier would be
If you add a wall do not add another vapor barrier
In my parent basement it was the same setup
I only built a 1/2 wall at the bottom & insulated the bottom
The wall went about about chair rail height
A 2x8 on the top of the wall provided a nice drink ledge all the way around
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Old 02-19-2009, 12:23 PM   #5
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Do I need to remove this?


I'm building a ceiling to floor wall, so if I remove the vapor barrier can I build right in front of it? or should I remove the old insualtion and everything right down to the concrete?
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Old 02-19-2009, 12:30 PM   #6
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Do I need to remove this?


Can i ask a dumb question (hope this doesnt hijack the thread but its sort of relevant)... Is this style of "half insulation" common to certain parts of the country? I live in NJ and have never ever seen a basement half insulated? Is it because in NJ most of the basements are completely underground? Do builders only insulate half when a majority is above ground?

I understand the science of doing it this way (frost line..etc) but i just never see it in NJ. I usually see no insulation at all. Clearly its originally an unfinished basement what was the point of half insulation? Maybe i don't see enough new houses. And almost invariably guys finish the basement and then the half wall is re-done.

(or taken advantage of with the drink shelf.. good idea). I guess what i'm saying is that most people never leave it as is.. so what was the point in the first place?
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Old 02-19-2009, 01:33 PM   #7
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Do I need to remove this?


yes, remove the vapor barrier and build a new wall. The top and bottom get treated differently since air flows in at the bottom and out at the top. Also the bottom may very well have adequate exterior insulation which is the best way to go. So if you heat this room and it stays heated for a while when the heat is off, you may not need any additional insulation. Or insulated the new wall is not a bad safety net and would not hurt anything. Then add a new sealed vapor barrier to this wall behind the sheetrock
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Old 02-19-2009, 02:00 PM   #8
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Do I need to remove this?


Quote:
Originally Posted by windowguy View Post
Can i ask a dumb question (hope this doesnt hijack the thread but its sort of relevant)... Is this style of "half insulation" common to certain parts of the country? I live in NJ and have never ever seen a basement half insulated? Is it because in NJ most of the basements are completely underground? Do builders only insulate half when a majority is above ground?

I understand the science of doing it this way (frost line..etc) but i just never see it in NJ. I usually see no insulation at all. Clearly its originally an unfinished basement what was the point of half insulation? Maybe i don't see enough new houses. And almost invariably guys finish the basement and then the half wall is re-done.

(or taken advantage of with the drink shelf.. good idea). I guess what i'm saying is that most people never leave it as is.. so what was the point in the first place?
Usually the point is to save on initial construction costs
A lot of houses are only 1/2 in the ground
Or the front of the house is fully underground, & the back is a walk out basement. In many cases a lot of people like it unfinished. They are not paying more for finish work, less livable space as far as purchase price. And they get to finish it & increase the value of their home

Say its 320 with unfinished basement, 380 with a finished basement. By doing the work after purchase they can "gain" an increase in value of the home

We have a stream on the property
So our basement will never be finished space

Last edited by Scuba_Dave; 02-19-2009 at 02:23 PM. Reason: sp
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Old 02-19-2009, 02:00 PM   #9
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Do I need to remove this?


You're going to need to prevent the concrete from transferring moisture to the walls. How are you going to do that? Concrete is like a giant sponge and contains a lot of moisture. The most common way to deal with this is to place your vapor barrier directly on the concrete and to place the bottom plate for the wall on top of the plastic as it lays on the floor. Your concrete walls will not be flat, so snap a line 3 3/4 inches or more, depending on concrete being plumb and straight. It's good to give a quarter inch space between the studs and concrete even with the plastic being there because it keeps the plastic from being punctured on the grit and sharp edges of concrete. I like to snap all the lines and then cut all the plates. After the bottom plate is secured, you can plumb up to locate and snap lines for all the top plates. Then just measure 6 or more at a time and toenail into place.
As a rule, always put the vapor barrier on the opposite side of which way the wall will dry during normal conditions. A concrete wall is only going to diffuse moisture into the air or materials it touches.
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Old 02-19-2009, 02:23 PM   #10
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Do I need to remove this?


Actually putting the vapor barrier against the concrete is a bad idea
If this is a newer house (looks it) then the tar on the outside of the foundation is a vapor barrier. Putting up insulation w/paper creates a vapor barrier on the inside. I would never put plastic right against concrete, that's just creating a space for mold to grow

Removing the plastic eliminates a total double vapor barrier
You want the wall OUT from the concrete at least 2" to allow air to circulate & any moisture to dry
Bottom plate of the wall MUST be PT or some other rot resistant wood. You should also have fire blocking in the wall every 10'
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Old 02-19-2009, 03:39 PM   #11
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Do I need to remove this?


I have posted a picture below what will happen to a wall with poly to the inside in the basement. This stuff is science. How will the wall dry? The basement wall only dries to the inside. I prescribed a vapor barrier to the concrete and this is what is recommended by science. Now, depending on where you are this could be polyethylene or 2" polystyrene. The fact of the matter is that the wall is going to give off moisture continuously whether you want it to or not and when that moisture gets in to the wall assembly, it has to go out and the only way is to the interior. If a plastic vapor barrier is preventing it, the wall will grow mold like crazy. A vapor barrier to the inside with proper insulation simply prevents the moisture from two things, condensing and migrating to the wall assembly at too fast a rate.


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Old 02-19-2009, 05:11 PM   #12
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So you simply moved the mold from the insulation to the wall
Problem not solved, just not seen
And that wall looks too close to the cement wall judging by the window
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Old 02-19-2009, 05:24 PM   #13
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Quote:
Originally Posted by Scuba_Dave View Post
We have a stream on the property
So our basement will never be finished space
You bought/built in a flood plain? Why?
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Old 02-19-2009, 05:34 PM   #14
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Do I need to remove this?


As long as there is sufficient insulation, no mold or mildew will grow on the inside because excessive moisture will not build and the water is being mitigated via the wall assembly. It's a procedure thats recommended and tested by research and approved by building inspectors and codes. The key is remembering that concrete always carries moisture and that the moisture has to be dealt with. Also remember that mold needs three things to grow...a surface, food, and moisture. If you allow the moisture to get to the wall assembly and stay there, you will have mold...however, if you allow controlled migration of the moisture to exit the wall assembly and not build, mold will not grow.
That said, every basement should have a way to condition the air to deal with the high relative humidity whether it be by a dehumidfier or an air exchanger.
Another must is a good perimeter drain and proper backfill.
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Old 02-19-2009, 06:00 PM   #15
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Do I need to remove this?


Quote:
Originally Posted by jogr View Post
You bought/built in a flood plain? Why?
House is 50 years old, not a flood plain
I'm building a 24x36 addition W/same size garage under
No need to finish the basement, storage only

Mold will grow anywhere it is trapped between the plastic & a damp cement wall. Cement is a surface

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