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Sealing/insulating exposed foundation


birch's Avatar
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Join Date: May 2002
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NY

04-25-16, 09:58 AM   #1  
Sealing/insulating exposed foundation

The room I am renovating has 2 exterior walls that are 4' cement foundation. Most is above grade. The 3rd pic shows a 10' section that is partially below grade due to a planting bed (u can see some mold).
Should I seal with dry lock or cover with a viper barrier?
The wall will be furred out 4". It was not insulated. Should I insulate? If so can I sue bats or do I need foam boards?
Cheers!


Last edited by birch; 04-25-16 at 10:20 AM.
 
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birch's Avatar
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04-27-16, 04:29 AM   #2  
I was having a tough time attaching pics. Hopefully this works
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04-27-16, 09:31 AM   #3  
I can't see the mold that clearly and only see two pictures. But what looks like mold on the lower portion of the wall, the concrete looks to have plastic over it.

A couple of problems here. One, the fiberglass insulation was installed without the drywall which would have served as an air barrier. Air seeps past the Kraft facing and reaches the cold exterior surface and deposits moisture and forms ice and ultimately mold. Second, the plastic on the lower portion trapped the moisture coming through the wall and may have again helped to grow mold.

Where vapor barriers are sometime used and even required, they must be part of a complete assembly. And, recent advice concerning insulation against a foundation tends to advise against a vapor barrier. Most often recommended would be to use 2" or whatever your code requires, of rigid foam, then your stud wall and fiber insulation to fill. The rigid insulation will allow a very small amount of drying to the inside and keep the inside surface warm enough to prevent condensation.

Link below:
Understanding Basements | Building Science Corporation

Bud

 
birch's Avatar
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04-29-16, 04:33 AM   #4  
Thanks bud. I have a few questions.
1. "A couple of problems here. One, the fiberglass insulation was installed without the drywall which would have served as an air barrier. "
What does this mean? There was not any insulation or vapor barrier over the foundation. The wall was furred out and had paneling.

2. Are you saying that insulation is only required on the section that is below grade? The part where there is a planting bed outside. Where the mold is. What about the rest that is above grade?

I have recently sealed all of the cement with dry lock. I will check the link for more info.
Cheers!

 
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04-29-16, 07:55 AM   #5  
1. During cold weather you would probably have found ice behind the drywall next to the sheathing. The paneling still would not have been an air barrier so there could have been moisture behind it as well. Any furring strips against the foundation needed to be pressure treated and correct fasteners used.
2. All walls need insulation in your climate and it should be at least minimum code level. Not sure what code you are currently under but here is a link for 2009.
https://energycode.pnl.gov/EnergyCod...ate=New%20York

Drylock is a water barrier ot a moisture barrier as in moisture vapor. That means the inside will still be increasing in moisture level trying to equalize with the outside. In most cases you omit a vapor barrier on the inside to prevent accumulation by drying to the inside.

Bud

 
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