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Kraft-Faced Insulation Under Sill Plate

SouthDakotaRoof | Posted in General Questions on

My house is a 1953 ranch style, poured concrete basement in zone 6A. My 2×4 walls had a fully bagged insulation of maybe mineral wool with kraft facing on both sides. Between my foundation and my sill plate is definatley kraft faced insulation, likely the same stuff from the walls just cut into strips. My floor framing is true 2x8s, and the only rot or water damage was from unflashed entry doors & unflashed porch.

I replaced the doors the correct way, removed the old porch, and replaced the damaged bit of rim joist. I am diy basement remodeling a full framing wall tear out, rebuild & foam board to modern  standards.

I am assuming that kraft facing does not prevent water wicking from foundation to the floors above. The house has survived 70 some years of this due to high levels of air passage drying everything up, I think.

Well, i removed everything to the studs on the exterior fully new in stud insulation, air sealed plywood sheathing (or at least my best attempt at it), eps, wrb, and smartside on a 1×4 rainscreen. Not so leaky now! The upper 3-1/2ish of my basement walls are above grade but covered by slate rock mortared over top the exterior foundation, it was done in the 70s says my neighbor

The drying potental of my vintage home & cement foundation has been reduced by my work so far & will be reduced even moreso as I intend to insulate the basement interior. Im assuming problems are going to start wicking their way into existance?

If i need to jack the house from inside to slip in a better sill seal (I have to do this, right?) I get how to do it on the end where the floor joists terminate into the rim, but how do I do this on the other two sides that dont have the joist ends?  Or am I not going to be able to get them hoisted for this purpose? If so then would i have to remove the slate from the outside surface for better drying safety? Or something im not aware of? In addition to these concerns my radon levels went from safe to way past 4 pci due to my sealing up so im going to now add radon remedation into the mix (begining with sealing the slab/foundation cracks & penetrations and redoing the attic again after the wiring update opened up a lot of light fixture penetrations  i had already sealed last winter. & Im shopping for a HRV for the basement)  whew, its a lot. I could really use some advice please. Thank you GBA.

*I couldnt find any mention of kraft insulation used this way when I googled- has anyone else seen or heard of this before? Is it a Regional thing or just a really unique choice by some hurried builder? Thanks again.

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  1. user-2310254 | | #1


    I will give your post a bump. Do you mean 3.5 inches of exposed foundation or 3.5 feet?

  2. Expert Member
    BILL WICHERS | | #2

    It sounds like you have some batt-type insulation smashed between the sill plate and the top of the masonry foundation wall as a sort of sill sealer? I've never seen that before. You're correct that kraft paper isn't a capillary break, you need something plastic or metal for that purpose.

    You don't necassarily have to put in a capillary break, but it's often a good idea, especially if you're planning on sealing up the masonry in some way (crawlspace liner, rigid foam insulation, etc.). I like to use thin (1/32") black HDPE sheet for this purpose because it's slippery, fairly stiff, and cheap. It's probably the easiest material to slide into a small gap to retrofit a capillary break into an old basement wall.


  3. user-5946022 | | #3

    Post a photos. It is hard to understand what you have based on the description.

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