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Concrete Moisture Meter … how to read

JeffBuck | Posted in Construction Techniques on May 13, 2008 10:04am

How do ya read a concrete moisture meter?

current job the gypspan over the radiant heat tubes is still damp.

hope to seal with red guard by this weekend.

 

GC borrowed a moisture meter … I haven’t seen it …

said he took some readings but it had three scales and he couldn’t convert to a percentage to tell him the actual moisture content.

I have no idea brand, make, model, style pins or pinless.

 

did some quick checking on the net … most of what I saw have a “reference scale” for the concrete modes … and most also has Green / Yellow / Red led’s that let ya know Yup, Maybe and Nope.

Looked like the ref scale for the green light was 0-85.

Yellow was 85-95

and Red was greater than 95.

 

are these numbers universal or brand specific.

I also don’t know what “numbers” he got a readings ….

hope his coordinate with what I can figure out.

 

I’ve never run into a rush job with a damp slab …

gotta see what Red Guard says is a good level to go on top of also.

 

any ideas? Just starting the search.

Jeff

    Buck Construction

 Artistry In Carpentry

     Pittsburgh Pa

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Replies

  1. dovetail97128 | May 13, 2008 10:52pm | #1

    How about using the universal meter?

    Piece of plastic laid on the gypcrete. If the underside shows moisture the next day you have problems.

    They can't get your Goat if you don't tell them where it is hidden.
  2. davidmeiland | May 14, 2008 12:13am | #2

    Jeff, we poured about 600SF of 1-1/2" gypcrete a few months back. It puts a LOT of moisture into the building, so I got a big dehumidifier in there and ran it for a while, but the gyp itself was dry and hard a few days after the pour. I would be careful about running a membrane over it unless you are sure the moisture has cured out. The gyp sub should be able to give you some guidelines--the sub that did our pour provided quite a bit of tech info on how to prep, what to expect, how to follow, etc. My tilesetter used redgard and fabric over the gyp in the bathroom and it seemed extremely tight to me once it was dry.

    I've heard a couple of horror stories about mold possibly caused by poured gyp. Who knows if they're true.

    1. User avater
      JeffBuck | May 14, 2008 10:54pm | #3

      from talking to the GC the gyp subs tells everyone a different story each time he's aslked a Q. Guess they had issues with him even leading up to this particular pour.

      the old plastic taped down was done on Mon ... came up dripping wet.

      the gypspan was poured last Monday.

      it was the gyp sub who told the HVAC sub to not worry about getting the heat on.

      for some reason the hvac sub took that to heart and took it a step farther to forget some parts to get the heat on after the GC said fire it up.

      looks like it's gonna be one of those jobs.

       

      I'll redo the old plastic test over Fri nite then probably make a bunch of panic'd calls from the driveway early sat morning ...

       

      that's usually how these things go.

      everyone wants yer opinion till U tell the truth and it screws up the pretend schedule

       

      Jeff    Buck Construction

       Artistry In Carpentry

           Pittsburgh Pa

      1. davidmeiland | May 14, 2008 11:15pm | #4

        You already know this but I can't stop myself.... I would be really careful running a membrane over gyp that isn't fully dry. If the moisture has to escape down thru the floor, and around the edges, it may cause mold and they'll try to hang you.

        The dehumidifier I rent is a Drizair 1100. It took about 4 gallons of water per day out of the house. I put it in there a little while after they did the gyp, and kept it a month, until the rockers were all done and gone and the primer was up. It made a huge difference.

        1. User avater
          JeffBuck | May 15, 2008 12:11am | #5

          the only thing pointing in my favor is the spec's on laying down the red guard.

          they have special instructions for going over GypSpan.

           

          I'm to cut the red guard one part to four parts cold / clean water.

          that's to go first as a primer coat.

           

          then, I can roll full strength right over that.

          my thinking ... they're not too worried about moisture in the slab, if the first step is to throw alot of moisture into the slab.

           

          I have read horrow stories about the red guard lifting pretty much in full sheets.

          some were found to be the GypSpan laid too wet to make it more fluid, which, this wasn't, as there's humps in the bigger rooms that have to be ground down. Guess when it's mixed "wet" is gets soft and chalky on top.

          the other's sounded like the primer step was skipped and if just didn't bond.

           

          if I was the GC I'd be worried about all the finish materials.

          They're trimming along with all this moisture and no heat.

           

          whole house is gonna move.

          Jeff    Buck Construction

           Artistry In Carpentry

               Pittsburgh Pa

          1. davidmeiland | May 15, 2008 04:09am | #6

            My tilesetter did pretty much that... thinned-down coat of redgard followed by full-strength with fabric embedded then I believe a second coat. I tried to peel one corner and it was tight.

  3. mizshredder2 | May 15, 2008 04:58am | #7

    "How do ya read a concrete moisture meter?"

    I use my eyes; but you're welcome to be more creative...

     

     

    G, D & R!

     

    "We choose our joys and sorrows long before we experience them."

     — Kahlil Gibran

    1. User avater
      JeffBuck | May 15, 2008 03:58pm | #8

      the way things are going on this job the GC may have been overlooking that part!

      Jeff    Buck Construction

       Artistry In Carpentry

           Pittsburgh Pa

      1. mizshredder2 | May 17, 2008 12:46am | #9

        roh roh

        doesn't sound good...........

         

        "We choose our joys and sorrows long before we experience them."

         — Kahlil Gibran

  4. Pelipeth | May 17, 2008 03:38am | #10

    Like the other man said plastic sheeting. 2x2 duct tape to floor, moisture the next morning means it's NOT cured.

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