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  • stuccoing dome over insulation details?

    hello... I'm getting closer to getting the oven on top of my constructed base, exciting! (should the hearth dry for at least a wk before loading it with the oven?)

    Once I mortar the dome joints and cover with insulation, how does one put a stucco surface on top of the 'squishy' surface of the insulation? I understand you can use the metal stucco lath available at home depot, but l'm not getting how it all stays together to allow the stucco to be applied artfully? is everything wired together somehow? is the lath somehow anchored to the hearth?

    I'd like to make this vaguely aesthetic, without having to start over when I mess it up.

    Any help appreciated.

    Ben

  • #2
    Re: stuccoing dome over insulation details?

    I formed the dome with rebar and then wrapped it with chicken wire. I filled the gap with the vermiculite/portland and then added some mortar on top. I tried to use the lath but it failed miserably.
    Last edited by Les; 09-12-2011, 09:47 PM.
    Check out my pictures here:
    http://www.fornobravo.com/forum/f8/les-build-4207.html

    If at first you don't succeed... Skydiving isn't for you.

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    • #3
      Re: stuccoing dome over insulation details?

      Ben,

      Many of us who built domes used some sort of rebar birdcage affair to which we tied our wire to support the stucco. It makes it easier to shape the quasi-hemisphere dome shape.

      Here's a link to my thread which shows the birdcage I built for my WFO. It was time consuming but made the actual task of stuccoing fairly easy. And at over three years so far no cracking.

      http://www.fornobravo.com/forum/43/s...html#post38564

      Hope this helps,
      Wiley

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      • #4
        Re: stuccoing dome over insulation details?

        Lots of builders cover the blanket with a layer of vermiculite/cement/water to get a nice shape, then stucco over that.
        Kindled with zeal and fired with passion.

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        • #5
          Re: stuccoing dome over insulation details?

          i did not use a fire blanket but only 4 inches of vermiculite concrete as my insulation then chichen wire and concrete render . if i was to build another oven i would let the vemiculite concrete fully cure and dry out totaly before i rendered my dome . i have added some pics of my vermiculite layerhttp://www.fornobravo.com/forum/members/emsoven-albums-vemiculite.html

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          • #6
            Re: stuccoing dome over insulation details?

            Hello,

            Once you use the metal lath to help form the shape you want your oven, you can use rebar ties to tie down the lath. Then you can apply the stucco directly over the lathe.

            Thanks,
            Heidi
            Last edited by HeidiL2011; 09-14-2011, 12:52 PM.

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            • #7
              Re: stuccoing dome over insulation details?

              Hi all

              Please excuse my ignorance i am a newbie after all but "Lathe" i have seen many references to this mythical beast but have as yet not stumbled across a description, where i come from a lathe is a metal / wood turning machine ...........please help!

              Thanks

              Gazz
              "I didn't touch it, it was like that when i found it..."

              Thanks

              Gazz

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              • #8
                Re: stuccoing dome over insulation details?

                Chicken wire is easier to shape. You can also cut it into short pieces which can be placed, overlapping each other under the stucco, as you go.the smaller pieces cope with the compound curve (curving in both directions)
                Kindled with zeal and fired with passion.

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                • #9
                  Re: stuccoing dome over insulation details?

                  thanks for the responses.... I can see I'll have to get creative, great.

                  so consensus is I need to make some kind of pencil rebar armature over the insulation? I see in the installation manual they talk about drilling 1/4" holes in the hearth to anchor the pencil rebar. Then cover with chicken wire.

                  does the gap NEED to be filled with vermiculite? the 3in ceramic insulation is spec for this oven, so more insulation, which may have some benefit for residual heat (I plan mostly pizzas, so high heat), is not strictly called for. Seems like some air gap would be fine, assuming my armature is strong enough to hold the stucco and abuse.

                  (the thought of having to mess around with another fill, e.g. vermiculite and cement, finding it and buying it, is giving me a headache.)

                  where does one get vermiculite BTW? I doubt its at the local HD.

                  thanks!

                  Ben

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                  • #10
                    Re: stuccoing dome over insulation details?

                    Gazz, it should be spelled lath, try a search of plaster and lath and you should get more info than you ever could need. Modern lath is a form of expanded metal where a sheet of metal is slit in a myriad of short slits in one direction and then pulled/stretched 90 degrees to the slits.

                    Ben, vermiculite is fairly common at nurseries and places that sell stuff for the garden. Our local "True Value Hardware" carries it but it can get spendy if purchased at such places. You can also get perlite at nurseries, it's sold as a soil additive for much the same purpose that one uses vermiculite (ie: hold moisture and lighten dense soils). Vermiculite is often used for insulation and in ground pool installers use it (beware some is siliconized so it is water repellent...not what you want if you are mixing it with cement and water expecting to make vermicrete)

                    Hope this helps,

                    Wiley

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                    • #11
                      Re: stuccoing dome over insulation details?

                      thanks Wiley... so perlite is the same a vermiculite?

                      thanks

                      ben

                      *** forget it I found the answer in the FB glossary, I guess they are the same thing. ben
                      Last edited by skinnydoc; 09-13-2011, 09:30 PM.

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                      • #12
                        Re: stuccoing dome over insulation details?

                        I would fill any gaps with vermiculite or perlite. It will help hold everything in place and give you more heat retention. I might even help your oven heat up faster.

                        Mike

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                        • #13
                          Re: stuccoing dome over insulation details?

                          Ben,
                          Perlite is made of small pieces of volcanic glass which have trapped water. These small chips are very rapidly heated to a high temperature where upon they pop sort of like popcorn.

                          Vermiculite is a form of the mineral mica. It comes from alluvial deposits and is also mined. Lots of bad press several years back from the stuff mined in Libby, Montana which also had serious levels of asbestos with the finished product. Vermiculite available today is closely checked to be free of asbestos.

                          So they are not the same material. Be sure to wear a filter mask when working with either product and gloves are recommended when working with perlite. Eye protection advisable as well.

                          I would also recommend filling any free areas between the high tech insulation and the dome shell with either product as they are better insulators than a simple void. I did that with my WFO and even after several hours of firing the outer shell is still ambient temperature.

                          Insulation is good.

                          Hope this helps,
                          Wiley

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                          • #14
                            Re: stuccoing dome over insulation details?

                            thanks guys...

                            so maybe just loose vermi- / perlite? I could rig up the mesh to be fine enough to retain it, or should I do the 6:1 vermicrete thing that FB talks about?

                            thanks for any details, very helpful in planning this out.

                            Ben

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                            • #15
                              Re: stuccoing dome over insulation details?

                              Ben,
                              I went the route of fine mesh...in my case I used window screen. My thoughts went like this: My whole WFO is an experiment and should I want to change something in the future I can simply bore a hole in the stucco and with a shop vac and suck out the vermiculite. Thus I can reuse the vermiculite. Also I didn't want the excess water to have to get out of the structure had I gone with vermicrete. My rebar birdcage is attached via construction adhesive to the stand. Should I need to modify something I can run a sawzall around the bottom and the whole outer shell could be lifted off as one piece, again for reuse (theoretically at least).

                              So far I have not had problems that would necessitate such drastic measures. I used to work in boatyards and one rule of thumb regarding boats: Close something up so you cannot get access to it and you will need to get access to repair, adjust or replace. Same rule seems to apply to most things.

                              I'm also a big believer is redundant systems and having spare parts, but that is my own craziness and off topic.

                              Bests,
                              Wiley

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