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leveling garage floor for living space

akgourmet | Posted in Construction Techniques on September 24, 2008 01:04am

I am re-doing a poorly done garage-to-family-room conversion and I need some help with the floor. It is currently a wavy, sloping concrete surface and I want to level it (or at least flatten) so I can install laminate. The room is 20’x20’and to make it perfectly level the low side will have to come up about 1.5″. Since premixed leveling compound is expensive compared to cement, I’m considering using a mortar mixture of 1 part portland cement, 2 parts lime and 9 parts sand. Is this a good idea? If I clean the existing surface thoroughly with a degreaser (Simple Green?) will the leveling mixture stick and not break up? I read on another website that I can use a cement and water mixture to “paint” the surface prior to filling to insure a good bond. Any thoughts?

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  1. User avater
    xxPaulCPxx | Sep 24, 2008 02:18am | #1

    There are acrylic products that will help you bond to the previous slab.  Goes on like watery elmers glue, dries like it too.

    Rebuilding my home in Cypress, CA
    Also a CRX fanatic!

    I don't feel it's healthy to keep your faults bottled up inside me.

  2. gordsco | Sep 24, 2008 03:23am | #2

    Why not insulate with polystyrene and install plywood floor on sleepers?

    The floor would be warmer.

    Or call a concrete truck and pour a level slab over the existing. Use wire mesh and don't worry about the bonding. 

     

  3. User avater
    Jeff_Clarke | Sep 24, 2008 03:48am | #3

    The SLC is expensive for a reason - it works.

    I would not recommend using the mortar mixture you describe, because it would llikely be much more than it is cracked up to be, if you know what I mean.

    Jeff

  4. Waters | Sep 24, 2008 03:58am | #4

    Around here you can't really do that without insulating--code wise.  I did one a while back with 2x4 sleepers and rigid foam as prev. described.  Then go wood subfloor over that.

    Far far superior to concrete alone under there.

     

  5. Billy | Sep 24, 2008 06:07am | #5

    You can reduce your SLC costs by using pea gravel as fill in the deep part of the pour.  The SLC manufacturers (or at least Custom Building Products) says it's OK.

    Billy

    1. akgourmet | Sep 24, 2008 08:42pm | #6

      thanks for the responses.  I don't want to use a sleeper system because of headroom and doorway transition issues.  The flooring will extend into a short hallway that leads to 2 bedrooms, a bath and a stairway. There is also a doorway on the opposite side that leads to the new attached garage. I might be able to use 1/2" foam board under the laminate for insulation, but definitely not 2x4's and plywood.

      What made me think of using mortar was this article:

      http://www.taunton.com/finehomebuilding/how-to/articles/mortar-what-type-need.aspx

      The type O should be sufficient for my purpose.  The current 20 year old slab is smooth and does not have any cracks, so the leveling compound just needs good compressive strength, which mortar does.  Maybe I'll use a latex additive to give it a little more flexibility, but I still think it  will work.  I already have a bag of cement and some sand left over from another project so I think I will mix up a batch and try it in a section.  I'll report back.

      The idea for the cement "paint" came from here:

      http://www.askthebuilder.com/429_Concrete_Overlays.shtml

       

      1. akgourmet | Mar 23, 2010 05:07pm | #7

        here's a quick update on my project.  It's been done for several months, but I just haven't gotten around to visiting this site. 

        My final mixture was 1 part portland cement to 3 parts sand and I used a bonding product to stick it to the slab.  I'd mix it up in a 5 gallon bucket and spread it with a straight 8' stud.  I lost count of the number of buckets I mixed up, but I used 100 lbs of cement.

         After I was satisfied with the fill and flatness, I layed down 6 mil poly, then 3/4" tongue and groove OSB and screwed it to the slab with Tapcon screws.  Layed laminate on top of that and it looks great with no soft spots or squeeks. 

        1. calvin | Mar 23, 2010 05:31pm | #8

          Way to go!

          People come back here on occasion and report back.

          You might have set the record for time gone.

          Thanks!

          How bout a picture of the project?

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