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Floor question - Forno Bravo Forum: The Wood-Fired Oven Community

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Floor question

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  • Floor question

    So I laid the floor bricks last night and granted I was thirsty and it was getting dark but I swear that in the night my bricks shifted a bit and left bigger gaps between them than when I laid them. Should I mix up a batch of refractory mortar and fill the gaps or will they be fine. There is a solid 4 1/2-5" of percrete underneath. Also if anyone is planning on building and running a thermocouple under the floor I beseech you to put a straw in the structural hearth layer to run the wire through. I tried for an hour to drill through the concrete before giving up and going from the side through the percrete.
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    antibacterial soap...just say no!

  • #2
    Re: Floor question

    I don't think the gaps are a problem. They will fill with wood ash quickly enough. I wouldn't mortar them.
    My geodesic oven project: part 1, part 2

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    • #3
      Re: Floor question

      Just make sure the surface feels level and doesn't catch a peel. I actually took a belt sander to mine, made the hearth surface as smooth as a baby's bottom (yes, thats a bit extreme - I just didn't like the end result of using an angle grinder)

      Ash WILL fill in the voids bwtween the bricks the first time (and every time) you brush your ashes

      RT

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      • #4
        Re: Floor question

        Thanks guys,
        I think I am going to try the belt sander method.
        antibacterial soap...just say no!

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        • #5
          Re: Floor question

          I filled my gaps with dry fireclay, left over from bedding down the floor bricks on the Cal Sil boards. It's practically the same composition as my bricks (40% alumina and 60% silica) so I assume it will behave in a similar manner thermally to the neighbouring bricks. Easy to fill even the narrowest of gaps, as it has the consistency of talc powder.

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          • #6
            Re: Floor question

            That was sort of my thought, to fill it with some thermal material. I just wondered
            a.) if it was neccessary to the oven's function and heat retention.
            b.) if I just used the dry clay if it wouldn't rear its head in my crusts.

            I love the response to questions on this forum. How helpful.
            antibacterial soap...just say no!

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            • #7
              Re: Floor question

              Ive seen a few of these same posts with the hearth bricks. A good tip to get these nice and flat is to have a rubber mallet on hand when laying them also using a notched trowel is 100% easier than trying to back butter them.
              Fire brick are pretty consistent in size, most of the problems people encounter I think is related to not moistening the bricks enough, soak those babies. If the bricks are nice and moist and have not wicked the moisture out of the fire clay mixture it will stay workable for a long time, long enough to beat the bricks into submission after getting them all down... try to keep them level as you go then go back and beat down the ones that are giving you trouble.

              As others have stated Don't fill the gaps they will fill themselves. Putting the fire clay in although sounds good in theory would be a disaster come bake time. In my opinion the hearth bricks are best left loose because there is a lot of movement going on. I'm curious about others who have mortared them together with the refractory mortar any separation? I'm on a quest to find out as much "field" information I can about this stuff..I'm Old School--fire clay but this stuffs got me excited if it really does what it says it does.
              Last edited by Unofornaio; 07-25-2007, 10:08 PM.
              http://www.palmisanoconcrete.com

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              • #8
                Re: Floor question

                I had a couple of places where the gaps were big enough to bother me. I know it has been said ash would fill those, but I thought it would be better to fill with refractory mortar. The reason being that with the same thermal characteristic as the brick, as Hendo said, the heat transmission would be better. Ash would seem to be more of an insulator. Now, I am glad I did. It is hard enough to get the heat to soak the floor as it is. I have 5 really high temp firings and the floor is as beautiful now as the day I finished it.

                As a note. I also wet mortared my floor down with HeatStop. But in reality it still floats. I just wanted it to be a solid mass that floats. I say that, because, I layed the insulation board with a layer of wet mortar for eveness, then did the same with the floor bricks on top.
                Last edited by wlively; 07-26-2007, 07:41 PM. Reason: addition
                Wade Lively

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                • #9
                  Re: Floor question

                  Chalk another one up for the refractory mortar..Thanks
                  http://www.palmisanoconcrete.com

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                  • #10
                    Re: Floor question

                    It still seems that the majority feel that they should be left alone. I don't think that I would do the fireclay by itself thinking that the wet dough would pull up the dust from that everytime I cooked. I am a big fan of waiting on things that can't be undone very easily so I will wait and see if I think the oven's preformance is affected before I use the mortar.
                    antibacterial soap...just say no!

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                    • #11
                      Re: Floor question

                      Part of my thinking which led me to fill the cracks with dry fireclay, were Paulages comments some time ago: “i think what i'll end up doing, is fireclay slip pan between the wall and floor, and under the wall and hearth” and “i saved all of the sludge from cutting the bricks (maybe 1/2-3/4 gal. worth), and plan to try using this as a paste to fill any gaps.” You’d need to go back to the posts to establish the context of these comments.

                      In the end, I decided on fireclay for the gaps on the cooking floor, and a 50/50 mix of fireclay and dried, sifted “sludge” from the cut bricks for the gap between the dome and floor (without making a paste – just applying it dry). I think whatever I did, I’ll still end up eating either fireclay or ash – probably the latter after a few bakes!

                      My refractory mortar came pre-mixed (wet), so I couldn’t easily fill the floor gaps, unlike a dry mix could do, but this sounds like a good idea.

                      I’m still wondering if I should have added some fine sand to the gap between the floor and dome, but I still ask myself – why? Time will tell I guess, but I ain’t vacuuming it out now!

                      Cheers, Paul.

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                      • #12
                        Re: Floor question

                        Um, sand would be an improvement how? Does it taste better or something?



                        "He is no fool who gives what he cannot keep to gain what he cannot lose." - Jim Elliot

                        "Success isn't permanent and failure isn't fatal." -Mike Ditka
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                        • #13
                          Re: Floor question

                          Your wit is much appreciated - brings me back down to earth again! I considered sand though due to the number of posts which recommend a 50/50 mix of fireclay and sand to bed the floor bricks down. I used just dry fireclay as it 'flowed' better when I plonked each brick down. With sand in the mix I found it more difficult to level each brick. P.

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