Basement waterproof/finishing in climate zone 4

Old 06-05-17, 02:54 PM
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Question Basement waterproof/finishing in climate zone 4

Hello all,

I purchased a house in Atlanta, GA (Climate Zone 4) four years ago which was originally built in 1986. Im about to start finishing the below grade basement (approx. 1600 sq ft total). Part of the basement is bounded by a poured in place concrete foundation wall. The remainder of the basement perimeter has already been framed/insulated fiberglass insulation between the studs. There are two windows & one door on the far side of the basement (opposite the foundation wall).

The basement has been dry for over a year now, ever since I hired a plumber to fix a microscopic leak in the main copper water line. I do have to run a dehumidifier for 2/3 of the year to limit the Georgia humidity. The basement is currently not under HVAC, but the furnace and AC is sized to accommodate the increased square footage once its finished.

Id like to install drywall on the foundation walls and minimize how much space we would lose for framing. Still debating whether or not I need to paint the Foundation Walls with a Water barrier paint (Drylok Latex or Bear Waterproof Acrylic). Might not be worth the hassle, since my 30-year basement appears to be dry?? House was built around 1986, so we don't know if they added a water proof barrier or insulation to the outside part of the concrete foundation wall.

I'm leaning toward "tongue and groove" XPS (rigid insulation) boards that are mounted directly to the Foundation Wall with appropriate liquid adhesive. Maybe 2 or 1.5 thick boards for good moisture resistance, mild insulation, and sound barrier. I now Owens Corning has the pink XPS boards and Dow has a similar blue XPS Styrofoam product.

Then mount steel Furring (aka Hat) Channels vertically through the XPS rigid boards, into the Foundation Wall with Ramset Power Actuated Gun & Ramset nails.

Then 4' x 8' moisture resistant drywall mounted to the Furring Channels with appropriate screws. This will leave a bit of cavity between the drywall and the XPS to help dampen sound on the basement walls with the concrete foundation. It would also allow any moisture to evaporate naturally if it ever came through the foundation wall and rigid XPS insulation boards.

Any Ramset experts know if the Ramset nails will blow through the 1.5 or 2" XPS board?

I really don't want to have problems with moisture in the walls down the road, however I really don't want to tear down all the drywall/rigid insulation on the concrete if it's not needed. From what I can read, we really don't need a whole lot of insulation in Climate Zone 4 (Atlanta) for below grade basements. The XPS acts more as a moisture resistant sound barrier with minor insulating value.
I would install regular drywall directly into the wood studs for the section that is already framed.

Any thoughts on this potential plan of action? Thanks for your advice.
Old 06-05-17, 03:09 PM
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In 1986 it's likely all they did to waterproof the exterior was install a drain [weeping] tile and coat the foundation with tar.

IMO it's better to build a 2x4 wall set out an inch or so from the foundation wall. That helps to alleviate any moisture issues that might come up along with giving you room to run the electrical.

almost forgot welcome to the forums!

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