Construction cardboard?

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Jan 30, 2023
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We have an unfinished basement. The top part of the wall is isolated from the ground by some sort of cardboard. This is not cardboard used for shipping boxes (which is corrugated), but is pretty much the same cardboard as found in hardcover books (at least older), but just pretty thick (3.5mm), dense and it seems to have some element-resistant features. One of such pieces was damaged by an animal while ago so I am looking for a piece to repair, but surprisingly, such material does not seem to be widely used. I checked in several Home Depot, Lowe's and Ace Hardware stores and nobody carry anything like that. Worst, nobody knows how it is exactly called. They sell Concrete Form Tubes, made from pretty much same material. Any help will be greatly appreciated.
Maybe a photo of the product, in application, will help.
Are you saying this product separates the concrete basement walls from the bottom plate of the wooden framed walls?

Google sill sealer or sill gasket and take a look at the photos that pop up and see if that helps.

If that is the problem it is not something that can be easily replaced or patched as the house sits on top of it. You may want to use a calking product to seal it up.
This is how it looks from the crawling space of the basement. You can see a small part of concrete piece of the porch showing right above the hole in the middle of the picture. You can see the cardboard covering the rest of the porch part at the top. The hole is where that cardboard was before it was damaged by a ground hog. If I open adjacent insulated areas, there are no holes and the cardboard is intact, going from top to the bottom.

My guess is it is a Fiber Expansion Joint Filler material sold in sheet form.

It could have been part of the forming for the basement walls and extended above the wall height and just left there. I wouldn’t think it should be below grade holding back the soil and the poured patio on top. I wonder if the grade was brought up after construction to pour the slab and that’s how it got this way.

I have never seen this before maybe others here will have a comment. It doesn’t look proper to me. Not sure what the fix would be without cutting the slab back and removing the soil and doing something different from the outside. In short term I would fill the hole with some metal flashing to keep the critters out