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Partial basement reno

Posted by garybsp (My Page) on
Wed, Feb 4, 09 at 13:26


I am planning on removing and replacing old walls in my basement in hopes of making it a more comfy living space.
The house was built in the late 1920s I believe.
The existing basement walls seem to be 2x2 studs and either wood chips (I know crazy), or fibreglass in between the studs, no vapor barrier and plywood walls. The subfloor is raised the width of a 2x4 (ie. 4 inches up). I'm not sure what moisture issues I will find when removing the walls but I plan to address them as I go. The basement seems to need dehumidification in the summer but there is no obvious moisture issues. On unfinished walls in the unfinished furnace/laundry room space maybe a little efflorescence.

Here's my plan. I plan to leave the subfloor in place as this would be cheaper than demolishing it and likely repouring concrete. I then plan on putting 2" XPS board on the walls and 2X3 studs over that and drywall over that.

I guess this is where I need some advice:

Should I be sealing the walls with something assuming they are not sealed already or will the XPS board be enough? If there is some efflorescence showing on the walls can I put the XPS board over this? Is all this worth it if a don't plan to do anything with the floor (ie. insulate it)? Lastly, do inside basement walls between finished and unfinished space need to be insulated or is this a no-no?

Thanks for any advice. In a perfect world if I had a lot of cash I'd hire out to get the basement done-up properly from scratch but I don't have the cash so I thought just replacing the walls might help the space become a little more comfy.


Follow-Up Postings:

RE: Partial basement reno

Dehumidification is always needed.

I wonder what the raised floor is over. I once bought a home that had a "finished" lowered basement. What I didn't realise was that it had been lowered by the removal of the concrete and setting of the 2x4s directly into the soil below.

I wouldn't seal the walls as most "sealants" trap the moisture moving from outside to inside in the summer and damage the walls. The efflorescence is likely due to the excessive humidity on the interior in the summer. Water vapour condenses on the wall and brings the salts to the surface. It wouldn't hurt to check outside water sources as well.

The distinction isn't between unfinished and finished. It is between conditioned and unconditioned space.

RE: Partial basement reno

Thanks worthy, I appreciate the comments.

I did remove a small bit of subfloor at one point to see what was under there. I'll take a closer look but it seems like just older concrete. I can't tell if it is heaving or cracked or moist, however. When the walls come down maybe I can access under the subfloor a litte easier and see. The furnace/laundry room area has no subfloor and by the looks of it more recently poured concrete. This concrete floor looks to be an inch and a half higher than the floor under the subfloor.

I have made sure that the downspouts take the water well away from the house.

Well the "finished" part of my basement is conditioned I think. At least if "conditioned" means hot air and return vents are installed. Is this what you mean by "conditioned"?

Thanks again.


RE: Partial basement reno

Building Science definition of conditioned space: "The part of the building that is designed to be thermally conditioned for the comfort of occupants or for other occupancies or for other reasons."

If you're merely in the Cold Zone of Canuckistan, you can more economically insulate the basement walls with a combination of 1" XPS and FG between the 2x3s than the 2"XPS. That's what I do here in Raccoon City (TO).


Instead of insulating between the finished and unfinished space, insulate and finish the foundation walls. No need for a great finish either--drywall and tape is enough. Otherwise your furnace is pumping heat to the outside. The greatest heat loss from the basement is the first four feet, especially the rim joist area.

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