Page 1 of 1

Basement Floor and Wall Insulation Prior to Slab

Posted: Fri Apr 26, 2019 12:13 pm
by mkicki
Hello, we are in the middle of building our home, currently all I have is the gravel in the basement and concrete foundation/framing done. Before I pour my slab, would like to get an idea of what is the best/most efficient option to insulate the basement. For now I bought the 2 inch rigid pink boards to lay on the gravel to install thermal heating prior to pouring the slab. I also have over 200 sheet of the .5 inch pink rigid board, should I use that on all walls as a moisture barrier as I already see 2 cracks on
the wall, thus to prevent future leaks? if so, should I use those boards all throughout the basement walls and then pour the concrete over them at the base? I was also thinking of using the 6mm plastic covering on the walls if not the .5 board. I will be finishing the basement up within a few months, haven't gotten around to see if we will do spray or rolls. The plan is to use 2x4s as the basement walls. I would like to get the best solution prior to pouring my slab. Thanks

Re: Basement Floor and Wall Insulation Prior to Slab

Posted: Fri Apr 26, 2019 9:13 pm
by Shannon
What do mean by “foundation/framing”?
What is your general location?

Re: Basement Floor and Wall Insulation Prior to Slab

Posted: Sun Apr 28, 2019 9:56 am
by mkicki
Sorry, I meant the house is pretty much up with framing done, and all mechanicals going in as we speak. So basement is currently just foundation walls and gravel on the floor. Want to plan all of this prior to pouring the slab. Location is Chicagoland suburbs.

Re: Basement Floor and Wall Insulation Prior to Slab

Posted: Sun Apr 28, 2019 10:24 am
by Shannon
yes your plans are all fine. I prefer the rigid foam on the walls as moisture barrier instead of poly because it gives you a thermal break as well. I prefer 1” foam because it gives you a better R factor.

Re: Basement Floor and Wall Insulation Prior to Slab

Posted: Wed May 08, 2019 9:29 am
by mkicki
Thank you Shannon, as a preference between the membrane type you would do with the rigid foam and use tape on the seams? what is the preferred way to attach the rigid board to the wall? I see minor cracks in the foundation already, that is why I want to make sure I get this all done prior to pouring the slab.

Re: Basement Floor and Wall Insulation Prior to Slab

Posted: Wed May 08, 2019 9:31 am
by mkicki
Also forgot to add, if I do use the .5 inch rigid foam as the barrier, in the future I can always spray closed cell to add more R value or any bat correct?

Re: Basement Floor and Wall Insulation Prior to Slab

Posted: Wed May 08, 2019 5:13 pm
by Shannon
yes if you are using the 1/2" foam tape the seams if you use something thicker with shiplap edges taping is not usually needed. Yes you can and should insulate more once the basement is framed.With 1/2" foam you can use some foam adhesive and the odd 1-1/2" Tapcon masonry screw with a larger washer on the head. Drill a hole and screw in the odd Tapcon to hold things in place.
Usually a moisture barrier is not really needed until you frame and finish the basement. It will not keep moisture out it only directs moisture to the floor instead of into the wall cavity and insulation. It is also really just for moisture due to frost or slight wicking through the concrete it is not meant to fix leaky basements . You should also have a proper water proofing installed on the exterior below grade and weeping tile to manage water.

Re: Basement Floor and Wall Insulation Prior to Slab

Posted: Thu May 09, 2019 9:35 am
by mkicki
My only concern is that I have this stuff https://www.homedepot.com/p/Owens-Corni ... /100320356

which I bought for exterior insulation prior to brick, which I don't need anymore, and was thinking of using it on the basement walls, reading through their site, I don't know if this can be used below grade, although it does looks like the 2 inch board that I used on the outside of the foundation below grade prior to back fill. My plan is to finish the basement within 6 months of completing the rest of the home, and will be laying 2 inch rigid foam under the slab with radiant heat installed as well. So you think just the .5 inch board won't be enough for any future water leaks, even if I install it on the wall all the way to the footing and the concrete slab will cover the board like 4 inches on the sides of each wall. I want to put all of this on prior to pour so that between the foundation wall and slab I have that 1/2 board, good idea?

Re: Basement Floor and Wall Insulation Prior to Slab

Posted: Thu May 09, 2019 7:52 pm
by Shannon
Oh it will for sure direct water down under the slab, I'm just saying that interior moisture barriers are not meant to be depended on to stop water penetration , exterior water proofing is a must. So i hope that you did that under your 2" foam?

Re: Basement Floor and Wall Insulation Prior to Slab

Posted: Fri May 10, 2019 7:24 am
by mkicki
Yes the contractor did some dampproofing black spray prior to the 2 inch board, but as an extra layer of protection, I want to do something from the inside as well cause who knows how long that black stuff will last.

Re: Basement Floor and Wall Insulation Prior to Slab

Posted: Fri May 10, 2019 8:36 pm
by Shannon
What you wanna do will work