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Basement exterior insulation over waterproofing

TNCave | Posted in General Questions on

Our basement exterior wall was waterproofed below grade today. The installation and warranty required the placement of material about 1/2” thick over the waterproofing. This material appears to be very permeable.

We are planning to insulate the basement from the exterior. Will this “unplanned” additional layer of permeable material cause any problems with our basement insulation? I was thinking that it might hold water if covered by rigid foam.

Any advice would be appreciated.



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  1. onslow | | #1


    The photos leave a lot of questions to ask. Is the fiberglass like material placed against the block wall first and then overcoated with what looks like bituminous goop? The second photo might have a strong shadow line which makes it look like the black goo is applied on both sides of the fiberglass mat. Is that the case? Any website to direct us to that would help explain the intent of the process and why the warranty requires the mat? What will be happening with the block portion not being waterproofed? Is this the area you intend to insulate with foam board and will it remain above grade?

  2. Jon_R | | #2

    Water or air that is trapped there won't matter. If it flows it would remove building heat that you are trying to retain.

  3. TNCave | | #3

    The process is an application of some sprayed on bituminous goo followed by a protective layer of some sort of fiber material. This is the process my builder uses on all below grade basements and is installed by a local contractor. The non waterproofed area is above grade. My intent is to cover it all with rigid foam, then mesh and stucco above grade and at the transition.

    I wasn’t certain now that we have this additional material that is permeable. Also, should we cut the exterior rigid foam along the same line as the fiber, eliminating any air gap above it, or does it not really matter?

    Thanks for the advice.


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