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Help with modular oven - decorative arch. - Forno Bravo Forum: The Wood-Fired Oven Community

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  • Help with modular oven - decorative arch.

    I hope someone can help. I've got my modular oven built up and have insulated with blanket and an inch or so of vermicrete. Today I built a decorative arch with firebricks cut in half but realise now that the oven and arch are not linked together and the arch can just fall forwards. I realised this when I was cleaning excess mortar off and the arch tilted forward slightly. Should I be thinking of maybe grinding out some mortar from the arch and embedding some wire ties to link to the render coats of the dome? Of if I extended the render coat to encompass the firebricks so that only the front face was showing?
    Up to now everything has gone fine and I feel stupid to have missed this in the planning. Anyone got any ideas?

  • #2
    Re: Help with modular oven - decorative arch.

    I wouldn't do any grinding . I would take the arch down, and start over, before I would do that! But, how about drilling? .
    joe watson

    "A year from now, you will wish that you had started today "

    My Build
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    • #3
      Re: Help with modular oven - decorative arch.

      I build my ovens this way. I have 8 wire ties in the arch that tie it to the outer shell. You simply attach your outer shell to the decorative arch. That way the whole of the inner parts of the oven are free to expand without placing pressure on the outer shell or decorative arch.
      Kindled with zeal and fired with passion.

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      • #4
        Re: Help with modular oven - decorative arch.

        Originally posted by Gulf View Post
        I wouldn't do any grinding . I would take the arch down, and start over, before I would do that! But, how about drilling? .
        With regard to drilling brick I worry that the vibration would only weaken the arch bond and make it fall down anyway, however if I drill the mortar when it is cured I might be able to clear out a small area without weakening it? Of should I try to do it before it cures and is still a llittle soft?

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        • #5
          Re: Help with modular oven - decorative arch.

          Originally posted by david s View Post
          I build my ovens this way. I have 8 wire ties in the arch that tie it to the outer shell. You simply attach your outer shell to the decorative arch. That way the whole of the inner parts of the oven are free to expand without placing pressure on the outer shell or decorative arch.
          In the UK we have wall ties which are stiff wires in a dumbbell shape which are used in construction of brick walls with a cavity to tie the two walls together, and are embedded in the mortar between layers. Sadly you can only buy them in large quantities and I need a handful. Do you think I could try to make some ties by knotting some wire and shoving it into holes drilled into the mortar before replacing the mortar?
          I understand the concept of tying the arch to the outer shell. However in all of my browsing of the forums I've never seen any reference of how builders join the arch to the main oven. Until now that is!

          I'll have a think.

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          • #6
            Re: Help with modular oven - decorative arch.

            I make my own wire ties and embed them in the cast arch. But if you build in brick you just pop them onto the mortar bed as you lay the bricks. This is faster, easier and stronger than drilling and screwing. Screws have a tendency to come loose when you start applying heat.
            Kindled with zeal and fired with passion.

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            • #7
              Re: Help with modular oven - decorative arch.

              Originally posted by david s View Post
              I make my own wire ties and embed them in the cast arch. But if you build in brick you just pop them onto the mortar bed as you lay the bricks. This is faster, easier and stronger than drilling and screwing. Screws have a tendency to come loose when you start applying heat.
              Great minds etc. I have cut up a couple of wire coat hangers, twisted the ends to give some purchase, and have drilled holes into the mortar between the bricks. I'll mortar them in the morning. One of the mortar wedges came a bit loose so I'll try and take it out and replace in full.

              How do you fix the wire ties at the other end? Presently they're on top of vermicrete layer. Should I put a small screw into the loop and screw slightly into the vermicrete and then embed in the scratch coat of render, or stucco, or just use render alone?

              I can't believe that this is the first issue I've had as a first time builder, with no experience, relying on this forum for guidance. Mind you, vermicrete was an absolute pig to work with...

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              • #8
                Re: Help with modular oven - decorative arch.

                I use much thinner wire than coat hanger stuff. Once you have some loops sticking out you can thread wire all over the dome and through your loops. This gives the outer shell (I'm assuming you are doing an igloo) something to hold onto and ties it into the decorative arch.
                Kindled with zeal and fired with passion.

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                • #9
                  Re: Help with modular oven - decorative arch.

                  I put chicken wire on the ceramic blanket and packed the vermicrete into it. Do I need to be putting more chicken wire on to reinforce the scratch coast of render? I was planning to just render onto the vermicrete, adding fibres to the first two costs for strength and flexibility, then a final finishing coat.

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                  • #10
                    Re: Help with modular oven - decorative arch.

                    Originally posted by RobDodds View Post
                    With regard to drilling brick I worry that the vibration would only weaken the arch bond and make it fall down anyway, however if I drill the mortar when it is cured I might be able to clear out a small area without weakening it? Of should I try to do it before it cures and is still a llittle soft?
                    Unless you use a hammerdrill , drilling wont be near as damaging as grinding. The sooner the better imo .
                    joe watson

                    "A year from now, you will wish that you had started today "

                    My Build
                    My Picasa Web Album

                    Comment


                    • #11
                      Re: Help with modular oven - decorative arch.

                      Originally posted by RobDodds View Post
                      ......I've never seen any reference of how builders join the arch to the main oven.
                      If you don't mind, I'm having trouble understanding what you mean by this. Are you talking about the arch for the oven opening or the vent arch? Maybe I should just stay off the forum until I get back from miami...my brain might have had it.
                      Old World Stone & Garden

                      Current WFO build - Dry Stone Base & Gothic Vault

                      When we build, let us think that we build for ever.
                      John Ruskin

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                      • #12
                        Re: Help with modular oven - decorative arch.

                        Originally posted by RobDodds View Post
                        I put chicken wire on the ceramic blanket and packed the vermicrete into it. Do I need to be putting more chicken wire on to reinforce the scratch coast of render? I was planning to just render onto the vermicrete, adding fibres to the first two costs for strength and flexibility, then a final finishing coat.
                        Yeah, I use fibres in the outer shell too, it's way faster than chicken wire.
                        Kindled with zeal and fired with passion.

                        Comment


                        • #13
                          Re: Help with modular oven - decorative arch.

                          So I ended up drilling into the mortar at the back of the decorative arch - not using the hammer drill but still a couple of wedges cracked out. Five thin wire ties were made from a cheap coat hanger and mortared into place. I've now applied the scratch coat of stucco, reinforced with glass fibres and the wire ties are buried in this, about 1 inch thick. Hopefully (not a word I like to use!) this will set up and secure the front arch sufficiently. I also plan to extend the next coats of stucco to partially enclose the arch so giving it more support. Arch form will be coming off tonight so we'll see!!!

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                          • #14
                            Re: Help with modular oven - decorative arch.

                            I'm not sure why you are worried about lateral pressure pushing your arch forward.
                            Old World Stone & Garden

                            Current WFO build - Dry Stone Base & Gothic Vault

                            When we build, let us think that we build for ever.
                            John Ruskin

                            Comment


                            • #15
                              Re: Help with modular oven - decorative arch.

                              Originally posted by stonecutter View Post
                              I'm not sure why you are worried about lateral pressure pushing your arch forward.
                              At this stage the only thing holding the arch in place is the mortar join at its base.I think this is what RobDodds means.
                              If you look carefully you can see the wire ties in the arch. I usually tie bits of coloured wool on to the ends so you can see them or they get easily buried by the vermicrete layer and are hard to find. They work as a depth gauge too.
                              Last edited by david s; 05-19-2014, 10:39 AM.
                              Kindled with zeal and fired with passion.

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