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Cracks in the joints on the back arch - Forno Bravo Forum: The Wood-Fired Oven Community



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Cracks in the joints on the back arch

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  • Cracks in the joints on the back arch

    After a lot of work I finally got the back arch to the oven completed. I thought it turned out good even though the middle 3 bricks gave me some problems. It isn’t the best looking but it will not be seen and I know what I need to do for the front arch. I went out to check on it this morning and saw cracks between the mortar and brick on 2 different joints (see attached pictures). I spray it down with my water bottle thinking it was only dry. I went back out later and the cracks are still there. This time I checked the structure and found that if I pushed up on the brick the entire middle portion moves.

    Info on what I did… Soaked the brinks for 30+ minutes, used Heatstop 50, and sprayed down entire arch with a water bottle multiple times the evening I built it.

    The only thing I could think of I didn’t do was not scoring the sides of the bricks (thought of that today when I found the problem).

    It isn’t 100% dry yet and I haven’t taken the form down.

    Should I wait a few days and see if the issue still exists? Should I take that portion off, remove the mortar, score the bricks and reset? Or…should I just keep building around it and hope the dome bricks hold it?



    Jeremy Ballanco

  • #2
    Re: Cracks in the joints on the back arch

    If it isn't solid now it isn't going to be later. It's easier to redo it now than later. I took 2 tries to get my first arch right.

    P.S. If you want to angle cut the bricks I have the Angleizer program. Send me a private msg with the span of your arch, rise, and brick size and I will send you the measurements to cut .
    Last edited by eprante; 04-07-2010, 02:29 PM.


    • #3
      Re: Cracks in the joints on the back arch

      I know this seems to be common wisdom on this board, but it is incorrect information for most applications: Do Not soak the bricks! If it is extremely hot (100+ degrees) and windy, it may be required to dip the bricks before placement, but NEVER soak them.

      The bond strength of the mortar relies upon the fact that the brick will draw moisture out of the mortar, and if it is saturated there will be no bond between the mortar and the brick.


      • #4
        Re: Cracks in the joints on the back arch

        I would second that advice. You don't want your bricks baked in the sun dry, but brickyards store them outside, and they arrive damp. This is how you want them. If you think they are dryer than that, a spray with a garden hose in the morning you use them will get them to the right humidity. You don't want surface water on the bricks.
        My geodesic oven project: part 1, part 2


        • #5
          Re: Cracks in the joints on the back arch

          My technique consisted of putting one session's worth of bricks in a low flat tub with the to-be-bonded surfaced fully submerged. However, as I retrieved a brick to start working on it I would very thoroughly tamp it on all sides with a thick towel. By the time I was buttering it up there was no water beading on it at all, it was just extremely undry. This practice worked very well for me.

          Website: http://keithwiley.com
          WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
          Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html


          • #6
            Re: Cracks in the joints on the back arch

            Thanks for the advice!

            As expected the bricks didn’t hold and I was able to pick them up very easily. The next question is do I reuse the set of 5 bricks that are bonded and try and put them back in the arch? I removed the mortar on the bricks so I have a clean surface to work with (see attached pictures). My first thought is to reuse the portion I took out but score the sides of the bricks with a grinder to give it something else to hold to. This would be the easiest but I would like to hear other people’s thoughts. While easy is nice I would rather do it right…

            Jeremy Ballanco


            • #7
              Re: Cracks in the joints on the back arch

              You need a frame to hold the arch and allow to dry for 3 days. Pending on mortar that you use it is difficult to say when it dries. My oven is still drying out when it cures.....


              • #8
                Re: Cracks in the joints on the back arch

                Looking back at the picture of the arch before you took it apart. The arch seems to have started going its own way with the 3rd brick on the left, that brick looks to be up off the form. I would be tempted to chisel that joint also and reset that brick so it rests flat down on the form. If you do that you probably won't be able to use the section that is still good. But it isn't going to be that hard to rebuild it. I was hesitant to take mine down because I struggled with it the first time. But the second time went much easier ( you get better with practice). Just pay attention to the joint thickness so when you get to the middle you have enough room for the center brick.

                A disclaimer: my entire masonry experience is doing my oven and there are several people on the blog with extensive experience- if they chime in with some advice that is different- listen to them.

                Good luck,