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Insulating a walk-out basement slab.

Snort | Posted in Construction Techniques on May 2, 2009 12:12pm

I’ve got one coming up, and I’ve never seen an attractive and energy efficient, yet abuse resistant solution. Whatchu got?

www.tvwsolar.com

Now I wish I could give Brother Bill his great thrill I would set him in chains at the top of the hill Then send out for some pillars and Cecil B. DeMille He could die happily ever after”

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  1. calvin | May 02, 2009 12:26am | #1

    A thermal break between the foundation wall and the slab of course.

    And one under the door threshold if you can detail it that way.  I've found you need to hug the wall with infloor radiant or you toes feel the chill as you get close to the door/wall.

    A separate stone sill can project out into the ozone, while maintaining separation from the slab.  Any slab movement will be at that point so hiding it under the threshold gives a bit of insurance to the finish flooring...........such as tile.

    A Great Place for Information, Comraderie, and a Sucker Punch.

    Remodeling Contractor just outside the Glass City.

    http://www.quittintime.com/

     

    1. Snort | May 02, 2009 01:34am | #2

      We were planning on a monolithic pour, turndown footing style. The backfilled parts will be Superior walls, 2x6 stud walls at the slab on grade.We can make the forms from below ground PT w/ rigid insulation inside, and leave the PT, but I've never like the look, or having foam below grade. It hasn't been a problem, yet, just looking for something better.Slab won't be radiant, spring and fall temp swings here can make it a bit uncomfortable.I like your door idea. The floor will be tiled.http://www.tvwsolar.com

      Now I wish I could give Brother Bill his great thrill

      I would set him in chains at the top of the hill

      Then send out for some pillars and Cecil B. DeMille

      He could die happily ever after"

      1. Snort | May 02, 2009 03:36pm | #3

        Bumpity bumphttp://www.tvwsolar.com

        Now I wish I could give Brother Bill his great thrill

        I would set him in chains at the top of the hill

        Then send out for some pillars and Cecil B. DeMille

        He could die happily ever after"

  2. User avater
    JonBlakemore | May 07, 2009 08:18am | #4

    I've never done this detail before, but have considered it. How many lineal feet of walkout are we talking about? I'm assuming it's 10' or less.

    Could you place some foam in the middle of the "wall" portion of the slab? If you have 4" of concrete on the outside, 2" of foam, and 4" concrete on the inside I would think you would have the best of both worlds. The interior edge of the foam would be covered by the 2x6 framing (assuming the sills are set in 1/2" for the sheathing to flush out with the foundation face) and you should have enough room for your anchor bolts.View Image

    I believe this is what the Dow T-Mass wall is, although I've never worked with that either.

     

    Jon Blakemore

    RappahannockINC.com Fredericksburg, VA

    1. Snort | May 07, 2009 03:29pm | #5

      Jon, That might work for a small section, but this is 85' with 4 corners.After looking at the new code requirements for insulating a turndown slab, we're bagging it, and maybe literally...might try the FastFoot form.Conventional footing, block to the top of the slab, beveled rigid foam inside. Solves a lot of problems, except for labor<G>http://www.tvwsolar.com

      Now I wish I could give Brother Bill his great thrill

      I would set him in chains at the top of the hill

      Then send out for some pillars and Cecil B. DeMille

      He could die happily ever after"

  3. Kivi | May 07, 2009 03:52pm | #6

    What about using a course of ICF blocks to form the downturn portion of the footing. Leave the outside edge with the foam intact, while the inside is lower to allow for the thickness of the floor.  You end up with a nice thermal break all the way around.  If you dont want to do parging/covering the outside foam directly, maybe use the ICF block with the built-in brick ledge,  onto which you could lay a veneer of concrete block as a durable exterior.  Near grade, the ICF foam on my house was just parged with concrete, and has held up fine for about 5 years so far.

    It's cold where I am so we also put a layer of rigid foam under the floor before it was poured.

    1. User avater
      JonBlakemore | May 07, 2009 07:34pm | #7

      How do you parge with concrete? I would think the aggregate, even if it was not that coarse, would present a problem. The parge coats I'm familiar with are 1/8"-1/2" thick. 

      Jon Blakemore RappahannockINC.com Fredericksburg, VA

      1. Kivi | May 07, 2009 08:10pm | #8

        sorry.. meant mortar i guess.. although there is a particular product for parging over the ICF foam.

    2. Snort | May 08, 2009 02:03am | #9

      I'm not as familiar with ICFs as I should be... I'll check them out.http://www.tvwsolar.com

      Now I wish I could give Brother Bill his great thrill

      I would set him in chains at the top of the hill

      Then send out for some pillars and Cecil B. DeMille

      He could die happily ever after"

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