Waterproofing basement walls


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Old 06-21-16, 01:40 PM
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Waterproofing basement walls

I am at the start of my basement finishing project and before I begin to install the rigid foam insulation against my cinder block walls I would to know if it is a good idea to waterproof the walls with something like Drylock or Zinnser Watertight before I do anything else.
 
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Old 06-21-16, 02:00 PM
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Hopefully all water issues have been resolved before you add the rigid. What is left is the moisture vapor and it passes through the blocks and if it hits a vapor barrier, the moisture level slowly equalizes until the extreior side of that VB is as wet as the soil outside. And check the description on Drylock, it doesn't block moisture vapor, good and bad.

What many choose to do is omit any vapor barrier and allow the moisture to dry to the inside right through the pink or blue rigid. Be sure the rigid you select does not have a foil or plastic face.

The key is to start with no moisture issues, liquid or vapor. What do you have.

Bud
 
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Old 06-21-16, 02:07 PM
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Waterproofing is done on the outside with gutters, downspout extensions and grading. Anything done on the inside is water mitigation.
 
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Old 06-21-16, 05:03 PM
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Bud,
I have the 1 inch green Kingspan xps rigid foam insulation sold at Lowes. Hopefully that is ok. Is there any special adhesive and tape I should be using?
 
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Old 06-21-16, 05:16 PM
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A quick look and that appears to be unfaced so not a true vapor barrier, which is fine. Some adhesives will dissolve the foam board so verify what you buy. I have used Loctite PL3 and it works great. With all adhesives you need something to hold them in place while the adhesive sets.

As for tape go with what is recommended for that foam board. It will be there for a long time and I've seen where the 2" packaging tape has been used and it falls off. Most any brand for foam board will probably work, but I prefer what they recommend.

I assume this will be getting a stud wall in front of that foam, with drywall?

Bud
 
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Old 06-21-16, 06:03 PM
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I bought tyvek tape and will double check if that is ok. I have seen where other people have used it successfully. After the rigid foamboard is installed I will install 2x4's and install 1/2 inch mold resistant drywall. I will also install unfaced r-13 batt insulation in the wall cavity. Hopefully this works out ok after all the research I have done.
 
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Old 06-21-16, 07:41 PM
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There are details as to how to build the walls, like treated 2x4 on the bottom in contact with the concrete, maybe a sill sealer layer under that. All fasteners that attach to the treated lumber need to be rater for that use. The back of the wall if above the foundation will need some drywall as a fire stop. No gap between wall and rigid unless it needs a little ti be vertical and straight. And no vapor barrier. Keep the drywall 3/4" off of the floor.

Luck
Bud
 
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Old 06-30-16, 05:02 AM
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Is the R13 unfaced wall insulation ok to use here? Or is that overkill? Also, since it is pretty hard to find unfaced wall insulation in my area, can I use faced and take the paper backing off?
 
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Old 06-30-16, 08:49 AM
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R-13 or Roxul R-15 should be fine. The Roxul comes without the facing and is dense enough to press fit between the studs and stay in place. My guess is, unfaced r-13 fiberglass is not available because it wouldn't stay in place as well. But, you can install the faced and then peel off the center 12" to defeat the vapor barrier issue. The face stapled edges will then hold the insulation in place.

Bud
 
 

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