I need help figuring out best solution to fix my basement moisture/mold issue...

As far as I can tell, water is entering at bottom seam of poured concrete wall and basement floor. I considered external waterproofing, but I was quoted $32K (105ft of external wall) and I cannot afford that.

I am thinking of getting Basement Systems' Waterguard perimeter french drain installed with thermaldry vapor barrier on the walls that channels any water from the concrete wall into waterguard (thermal dry is a bubble wrap type material with bubbles facing wall and an aluminum coating on the interior side. Essentially the bubbles let water make its way to the bottom where it leaks into french drain. Aluminum coating is supposed to reflect most of radiant heat back into the basement and provide some insulating value).

It would be installed like this: Thermaldry with Waterguard

I have few questions/concerns:

  1. There are vertical expansion cuts in poured concrete walls. These tend to leak after rains. How can I waterproof these cuts that are ~1/4" wide and run top to bottom on wall? I used epoxy to fix cracks in walls before, but I would need massive amounts of the stuff to fill up the voids. Is there something else I could use?

  2. Instead of thermaldry, I was going to use spray on closed cell insulation on the walls, but I am concerned with continued water seepage through cracks (I had several cracks over the years) & expansion cuts. What would happen if I had closed cell insulation sprayed on concrete walls with these leaks? Would water push insulation off the walls? Would it leak through?

  3. Is it a good idea to have a vapor barrier against concrete walls? This bubble stuff has some insulating value but I am worried, humidity will still condense on the inside surface of vapor barrier. Is there an insulated vapor barrier available that would provide a thermal break while channeling any water from concrete wall to french drain?

  4. I would like to avoid spraying foam insulation on thermaldry as it would probably void warranty. Can you think of a way I could install rigid XPS over thermaldry with no air gaps (and without voiding warranty)? I asked installer this question and waiting on answer.

  5. There's an 1/8" wide crack in floor (maybe 10' long) - how should I have it fixed?

  6. I was thinking of rebuilding finished walls as: corning seal gasket, pressure treated 2x4" plate, 2x4" studs 24" on center. Not sure about what insulation I should use (I guess depends on if I can get XPS installed over bubble wrap) and 1/2" drywall on outside.

I am probably over complicating things, but I would like to have a solution that channels water from walls while also having a good thermal break to avoid condensation. Any and all advice is appreciated!!!

2 Answers 2


As a home inspector, I always recommend to seal water intrusion from the exterior whenever and wherever possible. Since you mentioned a poured concrete foundation, I would recommend hiring a professional crack repair company.They can inject a flexible polymer substance into the length of the cracks that should seal them in most cases as long as the foundation is not still moving (and the crack is expanding).

Based on your comments, I would be more concerned that the foundation was not poured properly and/or does not have steel reinforcements in the concrete, and may cause more problems in the future. Until you get the cracking repaired and sealed I would not suggest putting up a finished basement, because then you would get what the previous commenter said would be mold.

For the crack in the floor, that is typical for a floating floor and can be fixed with some concrete polymer caulk. No big deal.

But then, this thread is three years old, so you may be long past this issue.


To prevent basement mold you should minimize moisture. Must hire a professional mold service to remove mold growing in the basement, especially if the mold growth is large.

  • There was minimal mold on baseboards only. I am trying to solve issue before it gets out of hand.
    – MRAK
    Aug 19, 2015 at 15:25

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