Replies

1. Expert Member
   MALCOLM TAYLOR | Nov 24, 2019 07:41pm | #1

   rdugan,

   No, although both approaches assume there is enough moisture to need channeling to the ground, and that dealing with it on the interior as a good strategy. My own feeling is that if you have that much moisture making it's way through the wall, you should try and stop it before it reaches the interior.

2. 
   rdugan | Nov 24, 2019 07:49pm | #2

   Thanks Malcolm,

   We've already addressed the major source of bulk water (overflowing gutters and improperly placed/terminated downspouts,) but after having to demo a finished basement due to water intrusion/mold, i'd like to be extra cautious. There are cracks in our poured cement foundation, which we will be repairing, but I'm sure that won't be the last of them. We are also adding an interior perimeter drain, and I'm thinking these channeled foam products could be an alternative to the dimple board - at least above the usual termination, if not altogether, considering we will also be insulating w/ foam.

   Also digging a trench to re-waterproof the exterior is prohibitive in our situation.

1. Expert Member
   MALCOLM TAYLOR | Nov 24, 2019 08:16pm | #3

   Given that I'd go with the channelled foam. However both products you are considering are for exterior foundation applications. Maybe it doesn't matter, or maybe there is a better one available?

1. 
   rdugan | Nov 25, 2019 06:34am | #4

   I had noticed they were only marketed for exterior, but assumed it wouldn't matter (although that was a main reason for asking my question.) Amvic has a similar product called Amdrain, which they even market as appropriate for below-grade interior, though am having a hard time locating a local distributor.

   In general though, I was just curious why more people haven't talked about this option. Maybe it's just too expensive?

1. 
   brendanalbano | Nov 25, 2019 10:40am | #5

   This is speculation, but it may just be a matter of dimple mat + foam solves the problem with two "regular" products. The channeled foam might be a specialty product in many regions, and even if it's easy to order, the barrier between "can pick it up at the lumberyard" vs. "have to special order it" seems like it's always a slightly bigger deal than I expect.

   Also, standard boilerplate if you haven't heard it already: XPS (in the U.S.) is produced with a blowing agent that has tremendously higher global warming potential than the blowing agents used in EPS. You should use EPS if at all possible.

3. 
   Jon_R | Nov 25, 2019 10:49am | #6

   > i'd like to be extra cautious

   I think many people with basements wish they had belt and suspenders when it comes to water entry.

   Unlike the exterior, the amount of bulk water reaching the interior of the wall should be small. As long as you don't run horizontal glue lines, my guess is that just taping smooth foam joints should keep water flowing downward (vs the problematic inward) . In a new build, lapping under-slab poly up and to the interior side of the wall foam should ensure that the water is directed under the slab (vs out onto the floor). You should use something similar (ie, water in the foam/concrete gap must be reliably directed to the drain).

1. Expert Member
   Dana Dorsett | Nov 25, 2019 02:10pm | #7

   >"As long as you don't run horizontal glue lines, my guess is that just taping smooth foam should keep water flowing downward (vs the problematic inward) ."

   That's a good point!

   Using blobs of adhesive rather than long beads for the initial mounting of the foam allows a micro-channel capillary break + drain space. Sealing just the top of the foam to the foundation as the only horizontal complete blockage is adequate for controlling convection around the foam layer.

2. 
   rdugan | Nov 25, 2019 06:53pm | #8

   This makes sense, though i wonder if this might cause just a bit more absorption / slower dry time? Despite the fact it should all be sealed, I really just don't love the idea of any more latent moisture inside the envelope than necessary. Any concerns w/ just routing my own micro channels in flat panels (maybe opens some cells causing higher absorption?)

   I was actually also wondering if i could completely forego the slab traversal barrier (dimple was suggested by contractors, as is commonly the case i believe?) and just seal the bottom of the foam to the slab - assuming the channels were shallower than the slab-wall gap (of course this would absolutely be the case if using flat panels.) We also have a sub-slab depressurization system for radon mitigation, and it seems it would be much easier to seal the top of foam panels (even if channeled) as opposed to dimple membrane.