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Discussion Forum

Mortar or Thinset

MikeHennessy | Posted in Construction Techniques on June 16, 2008 07:43am

I’m not a mason, and I don’t play one on TV, so maybe someone here can help me out.

I’m applying some sandstone (not fake stone) facing to a painted brick fireplace. I’ve Tapcon’d some diamond lath on the brick face and I’m ready to start laying up stone. The stone ranges from about 1″ thick to 2+” thick. Any advice on whether to stick it up with thinset vs. mortar? Should I use an admix for either?

Mike Hennessy
Pittsburgh, PA

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Replies

  1. User avater
    rjw | Jun 16, 2008 08:06pm | #1

    Thinset especially formulated for use with natural stone

    http://www.custombuildingproducts.com/ProductCatalog/SettingMaterials/MediumBedMortars/MarbleGraniteFortifiedPremium.aspx?user=arc&lang=en

    I'm not sure if the diamond lath is the right backer, though


    Remember Mary Dyer, a Christian Martyr (Thank you, Puritans)
    http://en.wikipedia.org/wiki/Mary_Dyer


    May your whole life become a response to the truth that you've always been loved, you are loved and you always will be loved" Rob Bell, Nooma, "Bullhorn"

    1. MikeHennessy | Jun 16, 2008 09:36pm | #3

      Diamond lath is what the stone yard said to use, so that's what I've done so far -- unless/until someone talks me out of it. ;-)

      Thanks for the stone set link.

      Mike HennessyPittsburgh, PA

      1. davidmeiland | Jun 16, 2008 09:52pm | #5

        Based on what you've already done, I don't think thinset is the right product for you, because of the diamond lath and also the possible thickness of mortar you need--you say the stone ranges from 1" to 2", and if you intend to make the face plane out the thinset will be much too thick.

        You can use most thinset up to maybe 3/8" thick without breaking too many laws. I would instead use mason's mix available in sacks. Caveat: talk to a tech rep at the company whose product you intend to use and describe your installation completely. They can give their blessing if appropriate.

        If you want to use thinset, I would float a mortar bed over the brick and lath first. It's definitely not a job for a first-timer, IMO.

         

        1. Notchman | Jun 16, 2008 10:18pm | #6

          I agree with David. Just use Type S mortar and parge it onto and into the lath....cover the lathe and make it as smooth as you can. When it's fairly stiff "comb" it; there is a tool for this, but you can also use a V-notched trowel (1/4- 3/8"). The purpose is to give bite to your layup mortar for the stone.It IS actually pretty easy to do, especially in the small area you have. Use a rubber trowel to parge onto the lathe...I use a black or white rubber trowel cause they last longer, but one of those red rubber tile grouting trowels works just fine.The real trick, if you haven't done it before, is to get the mortar just right; not too wet....you should be able to make a soft "snowball" out of it without it falling apart or oozing between your fingers.

          1. MikeHennessy | Jun 16, 2008 10:21pm | #8

            This sounds like the plan.

            Thanks.

            Mike HennessyPittsburgh, PA

        2. MikeHennessy | Jun 16, 2008 10:20pm | #7

          I don't really want the stone face planar. The stone yard guy said mortar would work -- I just wondered if thinset or using an admix with the mortar would be "stickier".

          I've laid stone before -- just haven't tried to bond it to a painted surface like this.

          Mike HennessyPittsburgh, PA

  2. User avater
    Heck | Jun 16, 2008 08:16pm | #2

    Hmmm. Painted brick. Needs either cbu screwed to it, or stucco lath and base coat, then the stone.

    Then mortar for the joints and thinset for the wall interface.

    I use just mortar on a vertical set like that.

    Inside or outside?

     


           

    1. MikeHennessy | Jun 16, 2008 09:39pm | #4

      It's inside. Only about 12 sq ft. -- just an area about 1' wide around a fireplace opening. As I replied to the earlier post, diamond lath was recommended by the stone yard -- I'm just fishing for a "second opinion".

      I suppose I could trowel a brown coat of mortar or something first, if that would be better.

      Mike HennessyPittsburgh, PA

  3. User avater
    JeffBuck | Jun 16, 2008 11:16pm | #9

    buy a nice bottle of wine ... cook a nice meal.

    then have big, scary, crazy Bob come over and install it however he wants!

     

    me ... not a mason either ... I'd be inclined to keep the lath and use mortar.

    bet either way U go it'll stay stuck.

    Jeff

        Buck Construction

     Artistry In Carpentry

         Pittsburgh Pa

    1. MikeHennessy | Jun 17, 2008 01:52am | #11

      "then have big, scary, crazy Bob come over and install it however he wants!"

      Shhhh. Don't tip him off. It'll be a surprise when he gets here for the pulled pork dinner.

      ;-)

      Mike HennessyPittsburgh, PA

      1. DanteO | Jun 17, 2008 02:28am | #16

        I would use Type M mortar...it's "stickier"

  4. Henley | Jun 17, 2008 01:49am | #10

    My plan would be-
    A scratch coat over the metal, finished with a "Scarifier"
    IE the tool previously mentioned to leave lots of scratches.
    Then butter the backs of the stones as I lay them.
    Oops- with type-S mortar.
    It never hurts to ad bonding agent (except for your tools).
    Then point the joints in at the end.

    This is your standard Cultured Stone method, and for all
    intents and purposes that is how your going to be working.

    Pre-wet the scratch coat, and keep your mud sticky but not wet.

    When you set a stone you kind of wiggle squish it in then
    hold still for a second or two.

    As you point, keep the mud dry enough that it doesn't smear.
    Just fill it up at first, then let it set up.
    come back later and compress the mud into the joint.
    Then strike it back to the required depth.
    When it is just barely workable, go over all the joint with
    a small stiff brush. Work the mud into all the nooks and crannies of the joints, while smoothing and evening them out.

    Long winded, and you probably already know this stuff, but
    hey just in case.

    Chuck

    1. MikeHennessy | Jun 17, 2008 01:54am | #12

      Sounds like we have a consensus. Thanks ALL.

      Mike HennessyPittsburgh, PA

    2. User avater
      JeffBuck | Jun 17, 2008 01:56am | #13

      I second the scratch coat method.

      Jeff    Buck Construction

       Artistry In Carpentry

           Pittsburgh Pa

  5. FNbenthayer | Jun 17, 2008 02:12am | #14

    Painted brick- I'd use a good modified thinset to scratch coat, then mortar.

     

     

     

     

    The awful thing is that beauty is mysterious as well as terrible. God and the devil are fighting there, and the battlefield is the heart of man.
    - Fyodor Dostoyevski

  6. segundo | Jun 17, 2008 02:22am | #15

    all I know about mortar is that if you mix mortar with a pitchfork, you are a mortar forker!

  7. MikeHennessy | Jul 08, 2008 12:21am | #17

    Well, using the advice of all here, I was able to re-face the brick with stone. Turned out pretty nice, too!

    I started with 4" sandstone and cut it down to 1" - 2" thick. Didn't do a two-coat mortar base -- just one, since it's such a small area and the brick mortar joints were deep enough to form a decent key. Before, during and after:

    View Image

    View Image

    View Image

    View Image

    Funny -- in the pics, the stone looks fake, but in person, it's pretty nice lookin' -- WAY better'n the fake stuff.

    Cap & trim on the chair rail, some EZ crown, and I'm done!

    Thanks again.

    Mike Hennessy
    Pittsburgh, PA

    1. User avater
      BillHartmann | Jul 08, 2008 07:11am | #18

      How about a close up of the corbells on the mantle.And the pattern on the sides. Are those inlays are just a pattern routed..
      .
      A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.

      1. MikeHennessy | Jul 08, 2008 02:57pm | #21

        "How about a close up of the corbells on the mantle."

        I'll snap a few more pics tonight and post 'em then.

        "And the pattern on the sides. Are those inlays are just a pattern routed."

        Both. I routed the cherry with a masonite template and then inlayed it with walnut. The circle at the bottom was a regular PIA to do. Kinda like a guitar soundhole rosette, but harder because it's smaller and a closed circle. Took 4 plys of walnut exactly .042" thick to fill the groove without cracking. I'm not in a big hurry to do it again. Between cutting the template and messing with trying to consistently cut those tiny walnut strips on my cheapo TS, these two panels took the better part of 6 hours.

        Mike HennessyPittsburgh, PA

      2. MikeHennessy | Jul 08, 2008 11:53pm | #24

        Here ya go on the closer pics. One of My Lovely Assistant oiling the mantel prior to completion (to be later finished off with shellac -- Frenchy'll love it!), and two more closer of the corbels and inlay. Shows off some nice curley cherry as well.

        View Image

        View Image

        View Image

         

        Mike HennessyPittsburgh, PA

         

         

        1. User avater
          BillHartmann | Jul 09, 2008 12:12am | #25

          That is what I did on my cherry mantle. Used an "oil". I expermimented and think that I used an oil/varnish finish. Then set it out in the sun for about 6 hours.Then shellaced it..
          .
          A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.

          1. MikeHennessy | Jul 09, 2008 02:16pm | #27

            I use danish oil/garnet shellac on cherry furniture a lot. I like the look, but I'm just a bit concerned that the heat from the fireplace won't be kind to the shellac. Shouldn't be a problem, but still, . . . .

            Mike HennessyPittsburgh, PA

          2. User avater
            BillHartmann | Jul 09, 2008 02:49pm | #29

            The heat wasn't in my case, but mine is a little higher..
            .
            A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.

        2. User avater
          JeffBuck | Jul 09, 2008 04:22am | #26

          that is some purty work!

           

          Jeff    Buck Construction

           Artistry In Carpentry

               Pittsburgh Pa

          1. MikeHennessy | Jul 09, 2008 02:19pm | #28

            Thanks, Jeff.

            Mike HennessyPittsburgh, PA

          2. User avater
            JeffBuck | Jul 10, 2008 04:40am | #30

            bet it looks even better in person.

             

            maybe from a seated position ...

            I dunno ... with a nice cold beer in hand ...

             

             

            free?

             

            just thinking out loud here.

            Jeff

                 Buck Construction

             Artistry In Carpentry

                 Pittsburgh Pa

          3. MikeHennessy | Jul 10, 2008 03:12pm | #31

            "bet it looks even better in person.maybe from a seated position ...I dunno ... with a nice cold beer in hand ... "

            LOL. Heck, it'll look better when it's DONE, beer or no -- I've been screwing around with this room for about two months now and I'm ready to be outa there!

            I'm at the point where everything needs to be prefinished before installing (everything that butts up to a wall/ceiling).

            I hate that part. I'd rather just cut, shoot, and worry about the finish later. (I always regret that when I'm trying to finish after the fact.)

            In this case, with a rubbed oil finish followed by shellac, there's no way I'd try that on this stuff after installation, so every piece has a 3 or 4-day wait time between cutting and installing.

            Fortunately, My Lovely Assistant has more patience than I.

            Mike HennessyPittsburgh, PA

  8. User avater
    McDesign | Jul 08, 2008 01:51pm | #19

    Thinset seems to harden very slowly in thick sections - a fist-sized leftover wad in a bucket will stay soft for a few days, while the same batch trowled thinly and used will stiffen right up.  Not sure how they do that.

    Forrest

    1. User avater
      BillHartmann | Jul 08, 2008 03:22pm | #22

      Are you talking about regular thinset or latex modified?This has come up in discussions about the type of thinset used with porclien tile and Ditra. The plain is cemment based and cures by chemical reaction.The modified needs to dry, for at least part of it's cure..
      .
      A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.

      1. User avater
        McDesign | Jul 08, 2008 07:03pm | #23

        Ah.  That would be the reason, I bet.  I haven't used Ditra yet.

        Forrest - rhyming

  9. Jer | Jul 08, 2008 02:03pm | #20

    It's been a while, but I used to do this. Mortar (mason's mix) over the lath, just enough to cover the wire, float it flat but leave it rough. Now use your thinset for natural stone with a 3/8" square notched trowel to set your sandstone.

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