I'm working on finishing my basement with 6 corners. The back wall is solid concrete with 4 corners (the garage is above one section). There is no moisture, and I plan on keeping it fresh with the two windows on the non-concrete side. Should I use both mortar waterproofing paint and r-tech insulation with drywall or pick one per wall? There is already wood and drywall in the basement too. How do I find regulations? I want to stay up to code. I'm in Georgia, USA. red is concrete; green side has a door and windows to outside

This is where the concrete wall gradually changes into an insulated wood wall

Back wall, bottom left of drawing

basement door

  • A basement with 6 corners. Does that mean the room is hexagonal? What does the number of corners have to do with the sealant selection? Where is the existing wood/drywall in relation to the section you're now looking to seal up? Maybe a picture or, at least, a drawing edited into your question would help.
    – FreeMan
    Commented Jan 5, 2022 at 15:25
  • I added a drawing and were the concrete wall connects to the outside wall
    – MoKi
    Commented Jan 5, 2022 at 16:36
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    Ah! You have a house on a hill. The foundation walls are poured concrete, but only extend upwards as much as necessary to hold back the dirt. Above that are standard 2x4 (or 2x6) framed walls to get up to the basement ceiling height. One wall is poured concrete all the way up because that wall is the one that's completely buried by dirt.
    – FreeMan
    Commented Jan 13, 2022 at 16:04
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    It seems to be the general consensus that coatings on the inside of concrete basement walls will fail. In order to control water, you needed to have a proper waterproofing membrane installed on the outside of the walls and, possibly a French drain to help any rain water run off to a better place. Assuming you have proper water proofing on the outside, you shouldn't really need to worry about it on the inside - just frame out as you normally would and apply insulation & drywall.
    – FreeMan
    Commented Jan 13, 2022 at 16:06
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    Are you sure there is no moisture? If you have no water collecting inside the basement that's great! But usually there will be moisture coming through the walls and floors that needs to be dealt with in the finishing plans. Tape a sheet of plastic to the wall, and lay down some plastic on the floor. Leave it for a few weeks that includes some heavy rainfall. See if the covered concrete becomes damp. If so, you need to plan to either contain the moisture at maximum (saturated) level or to create a ventilated air barrier. I think usually you just assume there is some dampness.
    – jay613
    Commented Jan 13, 2022 at 18:00

1 Answer 1


Code in your area possibly does not require insulation for below grade concrete wall.

If you wish to add insulation, apply XPS 1in to 2in thick, continuously along the concrete, then (1) add 2x3, 2x4 or 2x6 framing to fill with fibreglass, or (2) thin 1x4 strapping -without further insulation- for drywall backing.

XPS will keep concrete moisture out of the living space, but it is not a solution for wet exterior walls.

For aesthetic reasons you could build out the entire side wall floor to ceiling so that the finished above grade section is even with the below grade. You can build it out over the existing drywall, and no additional insulation will be required.

  • If it met code when built and you've done nothing to the foundation, then it still meets code. "coatings on the inside of concrete basement walls will fail" - "you needed to have a proper waterproofing membrane installed on the outside of the walls" - " I think usually you just assume there is some dampness."
    – Mazura
    Commented Jun 8, 2023 at 3:06

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